htc_mbox.c

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/*
 * Copyright (c) 2007-2011 Atheros Communications Inc.
 * Copyright (c) 2011-2012 Qualcomm Atheros, Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "core.h"
#include "hif.h"
#include "debug.h"
#include "hif-ops.h"
#include <asm/unaligned.h>

#define CALC_TXRX_PADDED_LEN(dev, len)  (__ALIGN_MASK((len), (dev)->block_mask))

static void ath6kl_htc_mbox_cleanup(struct htc_target *target);
static void ath6kl_htc_mbox_stop(struct htc_target *target);
static int ath6kl_htc_mbox_add_rxbuf_multiple(struct htc_target *target,
                          struct list_head *pkt_queue);
static void ath6kl_htc_set_credit_dist(struct htc_target *target,
                       struct ath6kl_htc_credit_info *cred_info,
                       u16 svc_pri_order[], int len);

/* threshold to re-enable Tx bundling for an AC*/
#define TX_RESUME_BUNDLE_THRESHOLD  1500

/* Functions for Tx credit handling */
static void ath6kl_credit_deposit(struct ath6kl_htc_credit_info *cred_info,
                  struct htc_endpoint_credit_dist *ep_dist,
                  int credits)
{
    ath6kl_dbg(ATH6KL_DBG_CREDIT, "credit deposit ep %d credits %d\n",
           ep_dist->endpoint, credits);

    ep_dist->credits += credits;
    ep_dist->cred_assngd += credits;
    cred_info->cur_free_credits -= credits;
}

static void ath6kl_credit_init(struct ath6kl_htc_credit_info *cred_info,
                   struct list_head *ep_list,
                   int tot_credits)
{
    struct htc_endpoint_credit_dist *cur_ep_dist;
    int count;

    ath6kl_dbg(ATH6KL_DBG_CREDIT, "credit init total %d\n", tot_credits);

    cred_info->cur_free_credits = tot_credits;
    cred_info->total_avail_credits = tot_credits;

    list_for_each_entry(cur_ep_dist, ep_list, list) {
        if (cur_ep_dist->endpoint == ENDPOINT_0)
            continue;

        cur_ep_dist->cred_min = cur_ep_dist->cred_per_msg;

        if (tot_credits > 4) {
            if ((cur_ep_dist->svc_id == WMI_DATA_BK_SVC) ||
                (cur_ep_dist->svc_id == WMI_DATA_BE_SVC)) {
                ath6kl_credit_deposit(cred_info,
                              cur_ep_dist,
                              cur_ep_dist->cred_min);
                cur_ep_dist->dist_flags |= HTC_EP_ACTIVE;
            }
        }

        if (cur_ep_dist->svc_id == WMI_CONTROL_SVC) {
            ath6kl_credit_deposit(cred_info, cur_ep_dist,
                          cur_ep_dist->cred_min);
            /*
             * Control service is always marked active, it
             * never goes inactive EVER.
             */
            cur_ep_dist->dist_flags |= HTC_EP_ACTIVE;
        }

        /*
         * Streams have to be created (explicit | implicit) for all
         * kinds of traffic. BE endpoints are also inactive in the
         * beginning. When BE traffic starts it creates implicit
         * streams that redistributes credits.
         *
         * Note: all other endpoints have minimums set but are
         * initially given NO credits. credits will be distributed
         * as traffic activity demands
         */
    }

    /*
     * For ath6kl_credit_seek function,
     * it use list_for_each_entry_reverse to walk around the whole ep list.
     * Therefore assign this lowestpri_ep_dist after walk around the ep_list
     */
    cred_info->lowestpri_ep_dist = cur_ep_dist->list;

    WARN_ON(cred_info->cur_free_credits <= 0);

    list_for_each_entry(cur_ep_dist, ep_list, list) {
        if (cur_ep_dist->endpoint == ENDPOINT_0)
            continue;

        if (cur_ep_dist->svc_id == WMI_CONTROL_SVC)
            cur_ep_dist->cred_norm = cur_ep_dist->cred_per_msg;
        else {
            /*
             * For the remaining data endpoints, we assume that
             * each cred_per_msg are the same. We use a simple
             * calculation here, we take the remaining credits
             * and determine how many max messages this can
             * cover and then set each endpoint's normal value
             * equal to 3/4 this amount.
             */
            count = (cred_info->cur_free_credits /
                 cur_ep_dist->cred_per_msg)
                * cur_ep_dist->cred_per_msg;
            count = (count * 3) >> 2;
            count = max(count, cur_ep_dist->cred_per_msg);
            cur_ep_dist->cred_norm = count;

        }

        ath6kl_dbg(ATH6KL_DBG_CREDIT,
               "credit ep %d svc_id %d credits %d per_msg %d norm %d min %d\n",
               cur_ep_dist->endpoint,
               cur_ep_dist->svc_id,
               cur_ep_dist->credits,
               cur_ep_dist->cred_per_msg,
               cur_ep_dist->cred_norm,
               cur_ep_dist->cred_min);
    }
}

/* initialize and setup credit distribution */
static int ath6kl_htc_mbox_credit_setup(struct htc_target *htc_target,
                   struct ath6kl_htc_credit_info *cred_info)
{
    u16 servicepriority[5];

    memset(cred_info, 0, sizeof(struct ath6kl_htc_credit_info));

    servicepriority[0] = WMI_CONTROL_SVC;  /* highest */
    servicepriority[1] = WMI_DATA_VO_SVC;
    servicepriority[2] = WMI_DATA_VI_SVC;
    servicepriority[3] = WMI_DATA_BE_SVC;
    servicepriority[4] = WMI_DATA_BK_SVC; /* lowest */

    /* set priority list */
    ath6kl_htc_set_credit_dist(htc_target, cred_info, servicepriority, 5);

    return 0;
}

/* reduce an ep's credits back to a set limit */
static void ath6kl_credit_reduce(struct ath6kl_htc_credit_info *cred_info,
                 struct htc_endpoint_credit_dist *ep_dist,
                 int limit)
{
    int credits;

    ath6kl_dbg(ATH6KL_DBG_CREDIT, "credit reduce ep %d limit %d\n",
           ep_dist->endpoint, limit);

    ep_dist->cred_assngd = limit;

    if (ep_dist->credits <= limit)
        return;

    credits = ep_dist->credits - limit;
    ep_dist->credits -= credits;
    cred_info->cur_free_credits += credits;
}

static void ath6kl_credit_update(struct ath6kl_htc_credit_info *cred_info,
                 struct list_head *epdist_list)
{
    struct htc_endpoint_credit_dist *cur_list;

    list_for_each_entry(cur_list, epdist_list, list) {
        if (cur_list->endpoint == ENDPOINT_0)
            continue;

        if (cur_list->cred_to_dist > 0) {
            cur_list->credits += cur_list->cred_to_dist;
            cur_list->cred_to_dist = 0;

            if (cur_list->credits > cur_list->cred_assngd)
                ath6kl_credit_reduce(cred_info,
                             cur_list,
                             cur_list->cred_assngd);

            if (cur_list->credits > cur_list->cred_norm)
                ath6kl_credit_reduce(cred_info, cur_list,
                             cur_list->cred_norm);

            if (!(cur_list->dist_flags & HTC_EP_ACTIVE)) {
                if (cur_list->txq_depth == 0)
                    ath6kl_credit_reduce(cred_info,
                                 cur_list, 0);
            }
        }
    }
}

/*
 * HTC has an endpoint that needs credits, ep_dist is the endpoint in
 * question.
 */
static void ath6kl_credit_seek(struct ath6kl_htc_credit_info *cred_info,
                struct htc_endpoint_credit_dist *ep_dist)
{
    struct htc_endpoint_credit_dist *curdist_list;
    int credits = 0;
    int need;

    if (ep_dist->svc_id == WMI_CONTROL_SVC)
        goto out;

    if ((ep_dist->svc_id == WMI_DATA_VI_SVC) ||
        (ep_dist->svc_id == WMI_DATA_VO_SVC))
        if ((ep_dist->cred_assngd >= ep_dist->cred_norm))
            goto out;

    /*
     * For all other services, we follow a simple algorithm of:
     *
     * 1. checking the free pool for credits
     * 2. checking lower priority endpoints for credits to take
     */

    credits = min(cred_info->cur_free_credits, ep_dist->seek_cred);

    if (credits >= ep_dist->seek_cred)
        goto out;

    /*
     * We don't have enough in the free pool, try taking away from
     * lower priority services The rule for taking away credits:
     *
     *   1. Only take from lower priority endpoints
     *   2. Only take what is allocated above the minimum (never
     *      starve an endpoint completely)
     *   3. Only take what you need.
     */

    list_for_each_entry_reverse(curdist_list,
                    &cred_info->lowestpri_ep_dist,
                    list) {
        if (curdist_list == ep_dist)
            break;

        need = ep_dist->seek_cred - cred_info->cur_free_credits;

        if ((curdist_list->cred_assngd - need) >=
             curdist_list->cred_min) {
            /*
             * The current one has been allocated more than
             * it's minimum and it has enough credits assigned
             * above it's minimum to fulfill our need try to
             * take away just enough to fulfill our need.
             */
            ath6kl_credit_reduce(cred_info, curdist_list,
                         curdist_list->cred_assngd - need);

            if (cred_info->cur_free_credits >=
                ep_dist->seek_cred)
                break;
        }

        if (curdist_list->endpoint == ENDPOINT_0)
            break;
    }

    credits = min(cred_info->cur_free_credits, ep_dist->seek_cred);

out:
    /* did we find some credits? */
    if (credits)
        ath6kl_credit_deposit(cred_info, ep_dist, credits);

    ep_dist->seek_cred = 0;
}

/* redistribute credits based on activity change */
static void ath6kl_credit_redistribute(struct ath6kl_htc_credit_info *info,
                       struct list_head *ep_dist_list)
{
    struct htc_endpoint_credit_dist *curdist_list;

    list_for_each_entry(curdist_list, ep_dist_list, list) {
        if (curdist_list->endpoint == ENDPOINT_0)
            continue;

        if ((curdist_list->svc_id == WMI_DATA_BK_SVC)  ||
            (curdist_list->svc_id == WMI_DATA_BE_SVC))
            curdist_list->dist_flags |= HTC_EP_ACTIVE;

        if ((curdist_list->svc_id != WMI_CONTROL_SVC) &&
            !(curdist_list->dist_flags & HTC_EP_ACTIVE)) {
            if (curdist_list->txq_depth == 0)
                ath6kl_credit_reduce(info, curdist_list, 0);
            else
                ath6kl_credit_reduce(info,
                             curdist_list,
                             curdist_list->cred_min);
        }
    }
}

/*
 *
 * This function is invoked whenever endpoints require credit
 * distributions. A lock is held while this function is invoked, this
 * function shall NOT block. The ep_dist_list is a list of distribution
 * structures in prioritized order as defined by the call to the
 * htc_set_credit_dist() api.
 */
static void ath6kl_credit_distribute(struct ath6kl_htc_credit_info *cred_info,
                     struct list_head *ep_dist_list,
                  enum htc_credit_dist_reason reason)
{
    switch (reason) {
    case HTC_CREDIT_DIST_SEND_COMPLETE:
        ath6kl_credit_update(cred_info, ep_dist_list);
        break;
    case HTC_CREDIT_DIST_ACTIVITY_CHANGE:
        ath6kl_credit_redistribute(cred_info, ep_dist_list);
        break;
    default:
        break;
    }

    WARN_ON(cred_info->cur_free_credits > cred_info->total_avail_credits);
    WARN_ON(cred_info->cur_free_credits < 0);
}

static void ath6kl_htc_tx_buf_align(u8 **buf, unsigned long len)
{
    u8 *align_addr;

    if (!IS_ALIGNED((unsigned long) *buf, 4)) {
        align_addr = PTR_ALIGN(*buf - 4, 4);
        memmove(align_addr, *buf, len);
        *buf = align_addr;
    }
}

static void ath6kl_htc_tx_prep_pkt(struct htc_packet *packet, u8 flags,
                   int ctrl0, int ctrl1)
{
    struct htc_frame_hdr *hdr;

    packet->buf -= HTC_HDR_LENGTH;
    hdr =  (struct htc_frame_hdr *)packet->buf;

    /* Endianess? */
    put_unaligned((u16)packet->act_len, &hdr->payld_len);
    hdr->flags = flags;
    hdr->eid = packet->endpoint;
    hdr->ctrl[0] = ctrl0;
    hdr->ctrl[1] = ctrl1;
}

static void htc_reclaim_txctrl_buf(struct htc_target *target,
                   struct htc_packet *pkt)
{
    spin_lock_bh(&target->htc_lock);
    list_add_tail(&pkt->list, &target->free_ctrl_txbuf);
    spin_unlock_bh(&target->htc_lock);
}

static struct htc_packet *htc_get_control_buf(struct htc_target *target,
                          bool tx)
{
    struct htc_packet *packet = NULL;
    struct list_head *buf_list;

    buf_list = tx ? &target->free_ctrl_txbuf : &target->free_ctrl_rxbuf;

    spin_lock_bh(&target->htc_lock);

    if (list_empty(buf_list)) {
        spin_unlock_bh(&target->htc_lock);
        return NULL;
    }

    packet = list_first_entry(buf_list, struct htc_packet, list);
    list_del(&packet->list);
    spin_unlock_bh(&target->htc_lock);

    if (tx)
        packet->buf = packet->buf_start + HTC_HDR_LENGTH;

    return packet;
}

static void htc_tx_comp_update(struct htc_target *target,
                   struct htc_endpoint *endpoint,
                   struct htc_packet *packet)
{
    packet->completion = NULL;
    packet->buf += HTC_HDR_LENGTH;

    if (!packet->status)
        return;

    ath6kl_err("req failed (status:%d, ep:%d, len:%d creds:%d)\n",
           packet->status, packet->endpoint, packet->act_len,
           packet->info.tx.cred_used);

    /* on failure to submit, reclaim credits for this packet */
    spin_lock_bh(&target->tx_lock);
    endpoint->cred_dist.cred_to_dist +=
                packet->info.tx.cred_used;
    endpoint->cred_dist.txq_depth = get_queue_depth(&endpoint->txq);

    ath6kl_dbg(ATH6KL_DBG_HTC, "htc tx ctxt 0x%p dist 0x%p\n",
           target->credit_info, &target->cred_dist_list);

    ath6kl_credit_distribute(target->credit_info,
                 &target->cred_dist_list,
                 HTC_CREDIT_DIST_SEND_COMPLETE);

    spin_unlock_bh(&target->tx_lock);
}

static void htc_tx_complete(struct htc_endpoint *endpoint,
                struct list_head *txq)
{
    if (list_empty(txq))
        return;

    ath6kl_dbg(ATH6KL_DBG_HTC,
           "htc tx complete ep %d pkts %d\n",
           endpoint->eid, get_queue_depth(txq));

    ath6kl_tx_complete(endpoint->target, txq);
}

static void htc_tx_comp_handler(struct htc_target *target,
                struct htc_packet *packet)
{
    struct htc_endpoint *endpoint = &target->endpoint[packet->endpoint];
    struct list_head container;

    ath6kl_dbg(ATH6KL_DBG_HTC, "htc tx complete seqno %d\n",
           packet->info.tx.seqno);

    htc_tx_comp_update(target, endpoint, packet);
    INIT_LIST_HEAD(&container);
    list_add_tail(&packet->list, &container);
    /* do completion */
    htc_tx_complete(endpoint, &container);
}

static void htc_async_tx_scat_complete(struct htc_target *target,
                       struct hif_scatter_req *scat_req)
{
    struct htc_endpoint *endpoint;
    struct htc_packet *packet;
    struct list_head tx_compq;
    int i;

    INIT_LIST_HEAD(&tx_compq);

    ath6kl_dbg(ATH6KL_DBG_HTC,
           "htc tx scat complete len %d entries %d\n",
           scat_req->len, scat_req->scat_entries);

    if (scat_req->status)
        ath6kl_err("send scatter req failed: %d\n", scat_req->status);

    packet = scat_req->scat_list[0].packet;
    endpoint = &target->endpoint[packet->endpoint];

    /* walk through the scatter list and process */
    for (i = 0; i < scat_req->scat_entries; i++) {
        packet = scat_req->scat_list[i].packet;
        if (!packet) {
            WARN_ON(1);
            return;
        }

        packet->status = scat_req->status;
        htc_tx_comp_update(target, endpoint, packet);
        list_add_tail(&packet->list, &tx_compq);
    }

    /* free scatter request */
    hif_scatter_req_add(target->dev->ar, scat_req);

    /* complete all packets */
    htc_tx_complete(endpoint, &tx_compq);
}

static int ath6kl_htc_tx_issue(struct htc_target *target,
                   struct htc_packet *packet)
{
    int status;
    bool sync = false;
    u32 padded_len, send_len;

    if (!packet->completion)
        sync = true;

    send_len = packet->act_len + HTC_HDR_LENGTH;

    padded_len = CALC_TXRX_PADDED_LEN(target, send_len);

    ath6kl_dbg(ATH6KL_DBG_HTC,
           "htc tx issue len %d seqno %d padded_len %d mbox 0x%X %s\n",
           send_len, packet->info.tx.seqno, padded_len,
           target->dev->ar->mbox_info.htc_addr,
           sync ? "sync" : "async");

    if (sync) {
        status = hif_read_write_sync(target->dev->ar,
                target->dev->ar->mbox_info.htc_addr,
                 packet->buf, padded_len,
                 HIF_WR_SYNC_BLOCK_INC);

        packet->status = status;
        packet->buf += HTC_HDR_LENGTH;
    } else
        status = hif_write_async(target->dev->ar,
                target->dev->ar->mbox_info.htc_addr,
                packet->buf, padded_len,
                HIF_WR_ASYNC_BLOCK_INC, packet);

    return status;
}

static int htc_check_credits(struct htc_target *target,
                 struct htc_endpoint *ep, u8 *flags,
                 enum htc_endpoint_id eid, unsigned int len,
                 int *req_cred)
{

    *req_cred = (len > target->tgt_cred_sz) ?
             DIV_ROUND_UP(len, target->tgt_cred_sz) : 1;

    ath6kl_dbg(ATH6KL_DBG_CREDIT, "credit check need %d got %d\n",
           *req_cred, ep->cred_dist.credits);

    if (ep->cred_dist.credits < *req_cred) {
        if (eid == ENDPOINT_0)
            return -EINVAL;

        /* Seek more credits */
        ep->cred_dist.seek_cred = *req_cred - ep->cred_dist.credits;

        ath6kl_credit_seek(target->credit_info, &ep->cred_dist);

        ep->cred_dist.seek_cred = 0;

        if (ep->cred_dist.credits < *req_cred) {
            ath6kl_dbg(ATH6KL_DBG_CREDIT,
                   "credit not found for ep %d\n",
                   eid);
            return -EINVAL;
        }
    }

    ep->cred_dist.credits -= *req_cred;
    ep->ep_st.cred_cosumd += *req_cred;

     /* When we are getting low on credits, ask for more */
    if (ep->cred_dist.credits < ep->cred_dist.cred_per_msg) {
        ep->cred_dist.seek_cred =
        ep->cred_dist.cred_per_msg - ep->cred_dist.credits;

        ath6kl_credit_seek(target->credit_info, &ep->cred_dist);

        /* see if we were successful in getting more */
        if (ep->cred_dist.credits < ep->cred_dist.cred_per_msg) {
            /* tell the target we need credits ASAP! */
            *flags |= HTC_FLAGS_NEED_CREDIT_UPDATE;
            ep->ep_st.cred_low_indicate += 1;
            ath6kl_dbg(ATH6KL_DBG_CREDIT,
                   "credit we need credits asap\n");
        }
    }

    return 0;
}

static void ath6kl_htc_tx_pkts_get(struct htc_target *target,
                   struct htc_endpoint *endpoint,
                   struct list_head *queue)
{
    int req_cred;
    u8 flags;
    struct htc_packet *packet;
    unsigned int len;

    while (true) {

        flags = 0;

        if (list_empty(&endpoint->txq))
            break;
        packet = list_first_entry(&endpoint->txq, struct htc_packet,
                      list);

        ath6kl_dbg(ATH6KL_DBG_HTC,
               "htc tx got packet 0x%p queue depth %d\n",
               packet, get_queue_depth(&endpoint->txq));

        len = CALC_TXRX_PADDED_LEN(target,
                       packet->act_len + HTC_HDR_LENGTH);

        if (htc_check_credits(target, endpoint, &flags,
                      packet->endpoint, len, &req_cred))
            break;

        /* now we can fully move onto caller's queue */
        packet = list_first_entry(&endpoint->txq, struct htc_packet,
                      list);
        list_move_tail(&packet->list, queue);

        /* save the number of credits this packet consumed */
        packet->info.tx.cred_used = req_cred;

        /* all TX packets are handled asynchronously */
        packet->completion = htc_tx_comp_handler;
        packet->context = target;
        endpoint->ep_st.tx_issued += 1;

        /* save send flags */
        packet->info.tx.flags = flags;
        packet->info.tx.seqno = endpoint->seqno;
        endpoint->seqno++;
    }
}

/* See if the padded tx length falls on a credit boundary */
static int htc_get_credit_padding(unsigned int cred_sz, int *len,
                  struct htc_endpoint *ep)
{
    int rem_cred, cred_pad;

    rem_cred = *len % cred_sz;

    /* No padding needed */
    if  (!rem_cred)
        return 0;

    if (!(ep->conn_flags & HTC_FLGS_TX_BNDL_PAD_EN))
        return -1;

    /*
     * The transfer consumes a "partial" credit, this
     * packet cannot be bundled unless we add
     * additional "dummy" padding (max 255 bytes) to
     * consume the entire credit.
     */
    cred_pad = *len < cred_sz ? (cred_sz - *len) : rem_cred;

    if ((cred_pad > 0) && (cred_pad <= 255))
        *len += cred_pad;
    else
        /* The amount of padding is too large, send as non-bundled */
        return -1;

    return cred_pad;
}

static int ath6kl_htc_tx_setup_scat_list(struct htc_target *target,
                     struct htc_endpoint *endpoint,
                     struct hif_scatter_req *scat_req,
                     int n_scat,
                     struct list_head *queue)
{
    struct htc_packet *packet;
    int i, len, rem_scat, cred_pad;
    int status = 0;
    u8 flags;

    rem_scat = target->max_tx_bndl_sz;

    for (i = 0; i < n_scat; i++) {
        scat_req->scat_list[i].packet = NULL;

        if (list_empty(queue))
            break;

        packet = list_first_entry(queue, struct htc_packet, list);
        len = CALC_TXRX_PADDED_LEN(target,
                       packet->act_len + HTC_HDR_LENGTH);

        cred_pad = htc_get_credit_padding(target->tgt_cred_sz,
                          &len, endpoint);
        if (cred_pad < 0 || rem_scat < len) {
            status = -ENOSPC;
            break;
        }

        rem_scat -= len;
        /* now remove it from the queue */
        list_del(&packet->list);

        scat_req->scat_list[i].packet = packet;
        /* prepare packet and flag message as part of a send bundle */
        flags = packet->info.tx.flags | HTC_FLAGS_SEND_BUNDLE;
        ath6kl_htc_tx_prep_pkt(packet, flags,
                       cred_pad, packet->info.tx.seqno);
        /* Make sure the buffer is 4-byte aligned */
        ath6kl_htc_tx_buf_align(&packet->buf,
                    packet->act_len + HTC_HDR_LENGTH);
        scat_req->scat_list[i].buf = packet->buf;
        scat_req->scat_list[i].len = len;

        scat_req->len += len;
        scat_req->scat_entries++;
        ath6kl_dbg(ATH6KL_DBG_HTC,
               "htc tx adding (%d) pkt 0x%p seqno %d len %d remaining %d\n",
               i, packet, packet->info.tx.seqno, len, rem_scat);
    }

    /* Roll back scatter setup in case of any failure */
    if (scat_req->scat_entries < HTC_MIN_HTC_MSGS_TO_BUNDLE) {
        for (i = scat_req->scat_entries - 1; i >= 0; i--) {
            packet = scat_req->scat_list[i].packet;
            if (packet) {
                packet->buf += HTC_HDR_LENGTH;
                list_add(&packet->list, queue);
            }
        }
        return -EAGAIN;
    }

    return status;
}

/*
 * Drain a queue and send as bundles this function may return without fully
 * draining the queue when
 *
 *    1. scatter resources are exhausted
 *    2. a message that will consume a partial credit will stop the
 *    bundling process early
 *    3. we drop below the minimum number of messages for a bundle
 */
static void ath6kl_htc_tx_bundle(struct htc_endpoint *endpoint,
                 struct list_head *queue,
                 int *sent_bundle, int *n_bundle_pkts)
{
    struct htc_target *target = endpoint->target;
    struct hif_scatter_req *scat_req = NULL;
    int n_scat, n_sent_bundle = 0, tot_pkts_bundle = 0;
    int status;
    u32 txb_mask;
    u8 ac = WMM_NUM_AC;

    if ((HTC_CTRL_RSVD_SVC != endpoint->svc_id) &&
        (WMI_CONTROL_SVC != endpoint->svc_id))
        ac = target->dev->ar->ep2ac_map[endpoint->eid];

    while (true) {
        status = 0;
        n_scat = get_queue_depth(queue);
        n_scat = min(n_scat, target->msg_per_bndl_max);

        if (n_scat < HTC_MIN_HTC_MSGS_TO_BUNDLE)
            /* not enough to bundle */
            break;

        scat_req = hif_scatter_req_get(target->dev->ar);

        if (!scat_req) {
            /* no scatter resources  */
            ath6kl_dbg(ATH6KL_DBG_HTC,
                   "htc tx no more scatter resources\n");
            break;
        }

        if ((ac < WMM_NUM_AC) && (ac != WMM_AC_BK)) {
            if (WMM_AC_BE == ac)
                /*
                 * BE, BK have priorities and bit
                 * positions reversed
                 */
                txb_mask = (1 << WMM_AC_BK);
            else
                /*
                 * any AC with priority lower than
                 * itself
                 */
                txb_mask = ((1 << ac) - 1);

            /*
             * when the scatter request resources drop below a
             * certain threshold, disable Tx bundling for all
             * AC's with priority lower than the current requesting
             * AC. Otherwise re-enable Tx bundling for them
             */
            if (scat_req->scat_q_depth < ATH6KL_SCATTER_REQS)
                target->tx_bndl_mask &= ~txb_mask;
            else
                target->tx_bndl_mask |= txb_mask;
        }

        ath6kl_dbg(ATH6KL_DBG_HTC, "htc tx pkts to scatter: %d\n",
               n_scat);

        scat_req->len = 0;
        scat_req->scat_entries = 0;

        status = ath6kl_htc_tx_setup_scat_list(target, endpoint,
                               scat_req, n_scat,
                               queue);
        if (status == -EAGAIN) {
            hif_scatter_req_add(target->dev->ar, scat_req);
            break;
        }

        /* send path is always asynchronous */
        scat_req->complete = htc_async_tx_scat_complete;
        n_sent_bundle++;
        tot_pkts_bundle += scat_req->scat_entries;

        ath6kl_dbg(ATH6KL_DBG_HTC,
               "htc tx scatter bytes %d entries %d\n",
               scat_req->len, scat_req->scat_entries);
        ath6kl_hif_submit_scat_req(target->dev, scat_req, false);

        if (status)
            break;
    }

    *sent_bundle = n_sent_bundle;
    *n_bundle_pkts = tot_pkts_bundle;
    ath6kl_dbg(ATH6KL_DBG_HTC, "htc tx bundle sent %d pkts\n",
           n_sent_bundle);

    return;
}

static void ath6kl_htc_tx_from_queue(struct htc_target *target,
                     struct htc_endpoint *endpoint)
{
    struct list_head txq;
    struct htc_packet *packet;
    int bundle_sent;
    int n_pkts_bundle;
    u8 ac = WMM_NUM_AC;
    int status;

    spin_lock_bh(&target->tx_lock);

    endpoint->tx_proc_cnt++;
    if (endpoint->tx_proc_cnt > 1) {
        endpoint->tx_proc_cnt--;
        spin_unlock_bh(&target->tx_lock);
        ath6kl_dbg(ATH6KL_DBG_HTC, "htc tx busy\n");
        return;
    }

    /*
     * drain the endpoint TX queue for transmission as long
     * as we have enough credits.
     */
    INIT_LIST_HEAD(&txq);

    if ((HTC_CTRL_RSVD_SVC != endpoint->svc_id) &&
        (WMI_CONTROL_SVC != endpoint->svc_id))
        ac = target->dev->ar->ep2ac_map[endpoint->eid];

    while (true) {

        if (list_empty(&endpoint->txq))
            break;

        ath6kl_htc_tx_pkts_get(target, endpoint, &txq);

        if (list_empty(&txq))
            break;

        spin_unlock_bh(&target->tx_lock);

        bundle_sent = 0;
        n_pkts_bundle = 0;

        while (true) {
            /* try to send a bundle on each pass */
            if ((target->tx_bndl_mask) &&
                (get_queue_depth(&txq) >=
                HTC_MIN_HTC_MSGS_TO_BUNDLE)) {
                int temp1 = 0, temp2 = 0;

                /* check if bundling is enabled for an AC */
                if (target->tx_bndl_mask & (1 << ac)) {
                    ath6kl_htc_tx_bundle(endpoint, &txq,
                                 &temp1, &temp2);
                    bundle_sent += temp1;
                    n_pkts_bundle += temp2;
                }
            }

            if (list_empty(&txq))
                break;

            packet = list_first_entry(&txq, struct htc_packet,
                          list);
            list_del(&packet->list);

            ath6kl_htc_tx_prep_pkt(packet, packet->info.tx.flags,
                           0, packet->info.tx.seqno);
            status = ath6kl_htc_tx_issue(target, packet);

            if (status) {
                packet->status = status;
                packet->completion(packet->context, packet);
            }
        }

        spin_lock_bh(&target->tx_lock);

        endpoint->ep_st.tx_bundles += bundle_sent;
        endpoint->ep_st.tx_pkt_bundled += n_pkts_bundle;

        /*
         * if an AC has bundling disabled and no tx bundling
         * has occured continously for a certain number of TX,
         * enable tx bundling for this AC
         */
        if (!bundle_sent) {
            if (!(target->tx_bndl_mask & (1 << ac)) &&
                (ac < WMM_NUM_AC)) {
                if (++target->ac_tx_count[ac] >=
                    TX_RESUME_BUNDLE_THRESHOLD) {
                    target->ac_tx_count[ac] = 0;
                    target->tx_bndl_mask |= (1 << ac);
                }
            }
        } else {
            /* tx bundling will reset the counter */
            if (ac < WMM_NUM_AC)
                target->ac_tx_count[ac] = 0;
        }
    }

    endpoint->tx_proc_cnt = 0;
    spin_unlock_bh(&target->tx_lock);
}

static bool ath6kl_htc_tx_try(struct htc_target *target,
                  struct htc_endpoint *endpoint,
                  struct htc_packet *tx_pkt)
{
    struct htc_ep_callbacks ep_cb;
    int txq_depth;
    bool overflow = false;

    ep_cb = endpoint->ep_cb;

    spin_lock_bh(&target->tx_lock);
    txq_depth = get_queue_depth(&endpoint->txq);
    spin_unlock_bh(&target->tx_lock);

    if (txq_depth >= endpoint->max_txq_depth)
        overflow = true;

    if (overflow)
        ath6kl_dbg(ATH6KL_DBG_HTC,
               "htc tx overflow ep %d depth %d max %d\n",
               endpoint->eid, txq_depth,
               endpoint->max_txq_depth);

    if (overflow && ep_cb.tx_full) {
        if (ep_cb.tx_full(endpoint->target, tx_pkt) ==
            HTC_SEND_FULL_DROP) {
            endpoint->ep_st.tx_dropped += 1;
            return false;
        }
    }

    spin_lock_bh(&target->tx_lock);
    list_add_tail(&tx_pkt->list, &endpoint->txq);
    spin_unlock_bh(&target->tx_lock);

    ath6kl_htc_tx_from_queue(target, endpoint);

    return true;
}

static void htc_chk_ep_txq(struct htc_target *target)
{
    struct htc_endpoint *endpoint;
    struct htc_endpoint_credit_dist *cred_dist;

    /*
     * Run through the credit distribution list to see if there are
     * packets queued. NOTE: no locks need to be taken since the
     * distribution list is not dynamic (cannot be re-ordered) and we
     * are not modifying any state.
     */
    list_for_each_entry(cred_dist, &target->cred_dist_list, list) {
        endpoint = cred_dist->htc_ep;

        spin_lock_bh(&target->tx_lock);
        if (!list_empty(&endpoint->txq)) {
            ath6kl_dbg(ATH6KL_DBG_HTC,
                   "htc creds ep %d credits %d pkts %d\n",
                   cred_dist->endpoint,
                   endpoint->cred_dist.credits,
                   get_queue_depth(&endpoint->txq));
            spin_unlock_bh(&target->tx_lock);
            /*
             * Try to start the stalled queue, this list is
             * ordered by priority. If there are credits
             * available the highest priority queue will get a
             * chance to reclaim credits from lower priority
             * ones.
             */
            ath6kl_htc_tx_from_queue(target, endpoint);
            spin_lock_bh(&target->tx_lock);
        }
        spin_unlock_bh(&target->tx_lock);
    }
}

static int htc_setup_tx_complete(struct htc_target *target)
{
    struct htc_packet *send_pkt = NULL;
    int status;

    send_pkt = htc_get_control_buf(target, true);

    if (!send_pkt)
        return -ENOMEM;

    if (target->htc_tgt_ver >= HTC_VERSION_2P1) {
        struct htc_setup_comp_ext_msg *setup_comp_ext;
        u32 flags = 0;

        setup_comp_ext =
            (struct htc_setup_comp_ext_msg *)send_pkt->buf;
        memset(setup_comp_ext, 0, sizeof(*setup_comp_ext));
        setup_comp_ext->msg_id =
            cpu_to_le16(HTC_MSG_SETUP_COMPLETE_EX_ID);

        if (target->msg_per_bndl_max > 0) {
            /* Indicate HTC bundling to the target */
            flags |= HTC_SETUP_COMP_FLG_RX_BNDL_EN;
            setup_comp_ext->msg_per_rxbndl =
                        target->msg_per_bndl_max;
        }

        memcpy(&setup_comp_ext->flags, &flags,
               sizeof(setup_comp_ext->flags));
        set_htc_pkt_info(send_pkt, NULL, (u8 *) setup_comp_ext,
                 sizeof(struct htc_setup_comp_ext_msg),
                 ENDPOINT_0, HTC_SERVICE_TX_PACKET_TAG);

    } else {
        struct htc_setup_comp_msg *setup_comp;
        setup_comp = (struct htc_setup_comp_msg *)send_pkt->buf;
        memset(setup_comp, 0, sizeof(struct htc_setup_comp_msg));
        setup_comp->msg_id = cpu_to_le16(HTC_MSG_SETUP_COMPLETE_ID);
        set_htc_pkt_info(send_pkt, NULL, (u8 *) setup_comp,
                 sizeof(struct htc_setup_comp_msg),
                 ENDPOINT_0, HTC_SERVICE_TX_PACKET_TAG);
    }

    /* we want synchronous operation */
    send_pkt->completion = NULL;
    ath6kl_htc_tx_prep_pkt(send_pkt, 0, 0, 0);
    status = ath6kl_htc_tx_issue(target, send_pkt);

    if (send_pkt != NULL)
        htc_reclaim_txctrl_buf(target, send_pkt);

    return status;
}

static void ath6kl_htc_set_credit_dist(struct htc_target *target,
                struct ath6kl_htc_credit_info *credit_info,
                u16 srvc_pri_order[], int list_len)
{
    struct htc_endpoint *endpoint;
    int i, ep;

    target->credit_info = credit_info;

    list_add_tail(&target->endpoint[ENDPOINT_0].cred_dist.list,
              &target->cred_dist_list);

    for (i = 0; i < list_len; i++) {
        for (ep = ENDPOINT_1; ep < ENDPOINT_MAX; ep++) {
            endpoint = &target->endpoint[ep];
            if (endpoint->svc_id == srvc_pri_order[i]) {
                list_add_tail(&endpoint->cred_dist.list,
                          &target->cred_dist_list);
                break;
            }
        }
        if (ep >= ENDPOINT_MAX) {
            WARN_ON(1);
            return;
        }
    }
}

static int ath6kl_htc_mbox_tx(struct htc_target *target,
                  struct htc_packet *packet)
{
    struct htc_endpoint *endpoint;
    struct list_head queue;

    ath6kl_dbg(ATH6KL_DBG_HTC,
           "htc tx ep id %d buf 0x%p len %d\n",
           packet->endpoint, packet->buf, packet->act_len);

    if (packet->endpoint >= ENDPOINT_MAX) {
        WARN_ON(1);
        return -EINVAL;
    }

    endpoint = &target->endpoint[packet->endpoint];

    if (!ath6kl_htc_tx_try(target, endpoint, packet)) {
        packet->status = (target->htc_flags & HTC_OP_STATE_STOPPING) ?
                 -ECANCELED : -ENOSPC;
        INIT_LIST_HEAD(&queue);
        list_add(&packet->list, &queue);
        htc_tx_complete(endpoint, &queue);
    }

    return 0;
}

/* flush endpoint TX queue */
static void ath6kl_htc_mbox_flush_txep(struct htc_target *target,
               enum htc_endpoint_id eid, u16 tag)
{
    struct htc_packet *packet, *tmp_pkt;
    struct list_head discard_q, container;
    struct htc_endpoint *endpoint = &target->endpoint[eid];

    if (!endpoint->svc_id) {
        WARN_ON(1);
        return;
    }

    /* initialize the discard queue */
    INIT_LIST_HEAD(&discard_q);

    spin_lock_bh(&target->tx_lock);

    list_for_each_entry_safe(packet, tmp_pkt, &endpoint->txq, list) {
        if ((tag == HTC_TX_PACKET_TAG_ALL) ||
            (tag == packet->info.tx.tag))
            list_move_tail(&packet->list, &discard_q);
    }

    spin_unlock_bh(&target->tx_lock);

    list_for_each_entry_safe(packet, tmp_pkt, &discard_q, list) {
        packet->status = -ECANCELED;
        list_del(&packet->list);
        ath6kl_dbg(ATH6KL_DBG_HTC,
               "htc tx flushing pkt 0x%p len %d  ep %d tag 0x%x\n",
               packet, packet->act_len,
               packet->endpoint, packet->info.tx.tag);

        INIT_LIST_HEAD(&container);
        list_add_tail(&packet->list, &container);
        htc_tx_complete(endpoint, &container);
    }

}

static void ath6kl_htc_flush_txep_all(struct htc_target *target)
{
    struct htc_endpoint *endpoint;
    int i;

    dump_cred_dist_stats(target);

    for (i = ENDPOINT_0; i < ENDPOINT_MAX; i++) {
        endpoint = &target->endpoint[i];
        if (endpoint->svc_id == 0)
            /* not in use.. */
            continue;
        ath6kl_htc_mbox_flush_txep(target, i, HTC_TX_PACKET_TAG_ALL);
    }
}

static void ath6kl_htc_mbox_activity_changed(struct htc_target *target,
                         enum htc_endpoint_id eid,
                         bool active)
{
    struct htc_endpoint *endpoint = &target->endpoint[eid];
    bool dist = false;

    if (endpoint->svc_id == 0) {
        WARN_ON(1);
        return;
    }

    spin_lock_bh(&target->tx_lock);

    if (active) {
        if (!(endpoint->cred_dist.dist_flags & HTC_EP_ACTIVE)) {
            endpoint->cred_dist.dist_flags |= HTC_EP_ACTIVE;
            dist = true;
        }
    } else {
        if (endpoint->cred_dist.dist_flags & HTC_EP_ACTIVE) {
            endpoint->cred_dist.dist_flags &= ~HTC_EP_ACTIVE;
            dist = true;
        }
    }

    if (dist) {
        endpoint->cred_dist.txq_depth =
            get_queue_depth(&endpoint->txq);

        ath6kl_dbg(ATH6KL_DBG_HTC,
               "htc tx activity ctxt 0x%p dist 0x%p\n",
               target->credit_info, &target->cred_dist_list);

        ath6kl_credit_distribute(target->credit_info,
                     &target->cred_dist_list,
                     HTC_CREDIT_DIST_ACTIVITY_CHANGE);
    }

    spin_unlock_bh(&target->tx_lock);

    if (dist && !active)
        htc_chk_ep_txq(target);
}

/* HTC Rx */

static inline void ath6kl_htc_rx_update_stats(struct htc_endpoint *endpoint,
                          int n_look_ahds)
{
    endpoint->ep_st.rx_pkts++;
    if (n_look_ahds == 1)
        endpoint->ep_st.rx_lkahds++;
    else if (n_look_ahds > 1)
        endpoint->ep_st.rx_bundle_lkahd++;
}

static inline bool htc_valid_rx_frame_len(struct htc_target *target,
                      enum htc_endpoint_id eid, int len)
{
    return (eid == target->dev->ar->ctrl_ep) ?
        len <= ATH6KL_BUFFER_SIZE : len <= ATH6KL_AMSDU_BUFFER_SIZE;
}

static int htc_add_rxbuf(struct htc_target *target, struct htc_packet *packet)
{
    struct list_head queue;

    INIT_LIST_HEAD(&queue);
    list_add_tail(&packet->list, &queue);
    return ath6kl_htc_mbox_add_rxbuf_multiple(target, &queue);
}

static void htc_reclaim_rxbuf(struct htc_target *target,
                  struct htc_packet *packet,
                  struct htc_endpoint *ep)
{
    if (packet->info.rx.rx_flags & HTC_RX_PKT_NO_RECYCLE) {
        htc_rxpkt_reset(packet);
        packet->status = -ECANCELED;
        ep->ep_cb.rx(ep->target, packet);
    } else {
        htc_rxpkt_reset(packet);
        htc_add_rxbuf((void *)(target), packet);
    }
}

static void reclaim_rx_ctrl_buf(struct htc_target *target,
                struct htc_packet *packet)
{
    spin_lock_bh(&target->htc_lock);
    list_add_tail(&packet->list, &target->free_ctrl_rxbuf);
    spin_unlock_bh(&target->htc_lock);
}

static int ath6kl_htc_rx_packet(struct htc_target *target,
                struct htc_packet *packet,
                u32 rx_len)
{
    struct ath6kl_device *dev = target->dev;
    u32 padded_len;
    int status;

    padded_len = CALC_TXRX_PADDED_LEN(target, rx_len);

    if (padded_len > packet->buf_len) {
        ath6kl_err("not enough receive space for packet - padlen %d recvlen %d bufferlen %d\n",
               padded_len, rx_len, packet->buf_len);
        return -ENOMEM;
    }

    ath6kl_dbg(ATH6KL_DBG_HTC,
           "htc rx 0x%p hdr 0x%x len %d mbox 0x%x\n",
           packet, packet->info.rx.exp_hdr,
           padded_len, dev->ar->mbox_info.htc_addr);

    status = hif_read_write_sync(dev->ar,
                     dev->ar->mbox_info.htc_addr,
                     packet->buf, padded_len,
                     HIF_RD_SYNC_BLOCK_FIX);

    packet->status = status;

    return status;
}

/*
 * optimization for recv packets, we can indicate a
 * "hint" that there are more  single-packets to fetch
 * on this endpoint.
 */
static void ath6kl_htc_rx_set_indicate(u32 lk_ahd,
                       struct htc_endpoint *endpoint,
                       struct htc_packet *packet)
{
    struct htc_frame_hdr *htc_hdr = (struct htc_frame_hdr *)&lk_ahd;

    if (htc_hdr->eid == packet->endpoint) {
        if (!list_empty(&endpoint->rx_bufq))
            packet->info.rx.indicat_flags |=
                    HTC_RX_FLAGS_INDICATE_MORE_PKTS;
    }
}

static void ath6kl_htc_rx_chk_water_mark(struct htc_endpoint *endpoint)
{
    struct htc_ep_callbacks ep_cb = endpoint->ep_cb;

    if (ep_cb.rx_refill_thresh > 0) {
        spin_lock_bh(&endpoint->target->rx_lock);
        if (get_queue_depth(&endpoint->rx_bufq)
            < ep_cb.rx_refill_thresh) {
            spin_unlock_bh(&endpoint->target->rx_lock);
            ep_cb.rx_refill(endpoint->target, endpoint->eid);
            return;
        }
        spin_unlock_bh(&endpoint->target->rx_lock);
    }
}

/* This function is called with rx_lock held */
static int ath6kl_htc_rx_setup(struct htc_target *target,
                   struct htc_endpoint *ep,
                   u32 *lk_ahds, struct list_head *queue, int n_msg)
{
    struct htc_packet *packet;
    /* FIXME: type of lk_ahds can't be right */
    struct htc_frame_hdr *htc_hdr = (struct htc_frame_hdr *)lk_ahds;
    struct htc_ep_callbacks ep_cb;
    int status = 0, j, full_len;
    bool no_recycle;

    full_len = CALC_TXRX_PADDED_LEN(target,
                    le16_to_cpu(htc_hdr->payld_len) +
                    sizeof(*htc_hdr));

    if (!htc_valid_rx_frame_len(target, ep->eid, full_len)) {
        ath6kl_warn("Rx buffer requested with invalid length htc_hdr:eid %d, flags 0x%x, len %d\n",
                htc_hdr->eid, htc_hdr->flags,
                le16_to_cpu(htc_hdr->payld_len));
        return -EINVAL;
    }

    ep_cb = ep->ep_cb;
    for (j = 0; j < n_msg; j++) {

        /*
         * Reset flag, any packets allocated using the
         * rx_alloc() API cannot be recycled on
         * cleanup,they must be explicitly returned.
         */
        no_recycle = false;

        if (ep_cb.rx_allocthresh &&
            (full_len > ep_cb.rx_alloc_thresh)) {
            ep->ep_st.rx_alloc_thresh_hit += 1;
            ep->ep_st.rxalloc_thresh_byte +=
                le16_to_cpu(htc_hdr->payld_len);

            spin_unlock_bh(&target->rx_lock);
            no_recycle = true;

            packet = ep_cb.rx_allocthresh(ep->target, ep->eid,
                              full_len);
            spin_lock_bh(&target->rx_lock);
        } else {
            /* refill handler is being used */
            if (list_empty(&ep->rx_bufq)) {
                if (ep_cb.rx_refill) {
                    spin_unlock_bh(&target->rx_lock);
                    ep_cb.rx_refill(ep->target, ep->eid);
                    spin_lock_bh(&target->rx_lock);
                }
            }

            if (list_empty(&ep->rx_bufq))
                packet = NULL;
            else {
                packet = list_first_entry(&ep->rx_bufq,
                        struct htc_packet, list);
                list_del(&packet->list);
            }
        }

        if (!packet) {
            target->rx_st_flags |= HTC_RECV_WAIT_BUFFERS;
            target->ep_waiting = ep->eid;
            return -ENOSPC;
        }

        /* clear flags */
        packet->info.rx.rx_flags = 0;
        packet->info.rx.indicat_flags = 0;
        packet->status = 0;

        if (no_recycle)
            /*
             * flag that these packets cannot be
             * recycled, they have to be returned to
             * the user
             */
            packet->info.rx.rx_flags |= HTC_RX_PKT_NO_RECYCLE;

        /* Caller needs to free this upon any failure */
        list_add_tail(&packet->list, queue);

        if (target->htc_flags & HTC_OP_STATE_STOPPING) {
            status = -ECANCELED;
            break;
        }

        if (j) {
            packet->info.rx.rx_flags |= HTC_RX_PKT_REFRESH_HDR;
            packet->info.rx.exp_hdr = 0xFFFFFFFF;
        } else
            /* set expected look ahead */
            packet->info.rx.exp_hdr = *lk_ahds;

        packet->act_len = le16_to_cpu(htc_hdr->payld_len) +
            HTC_HDR_LENGTH;
    }

    return status;
}

static int ath6kl_htc_rx_alloc(struct htc_target *target,
                   u32 lk_ahds[], int msg,
                   struct htc_endpoint *endpoint,
                   struct list_head *queue)
{
    int status = 0;
    struct htc_packet *packet, *tmp_pkt;
    struct htc_frame_hdr *htc_hdr;
    int i, n_msg;

    spin_lock_bh(&target->rx_lock);

    for (i = 0; i < msg; i++) {

        htc_hdr = (struct htc_frame_hdr *)&lk_ahds[i];

        if (htc_hdr->eid >= ENDPOINT_MAX) {
            ath6kl_err("invalid ep in look-ahead: %d\n",
                   htc_hdr->eid);
            status = -ENOMEM;
            break;
        }

        if (htc_hdr->eid != endpoint->eid) {
            ath6kl_err("invalid ep in look-ahead: %d should be : %d (index:%d)\n",
                   htc_hdr->eid, endpoint->eid, i);
            status = -ENOMEM;
            break;
        }

        if (le16_to_cpu(htc_hdr->payld_len) > HTC_MAX_PAYLOAD_LENGTH) {
            ath6kl_err("payload len %d exceeds max htc : %d !\n",
                   htc_hdr->payld_len,
                   (u32) HTC_MAX_PAYLOAD_LENGTH);
            status = -ENOMEM;
            break;
        }

        if (endpoint->svc_id == 0) {
            ath6kl_err("ep %d is not connected !\n", htc_hdr->eid);
            status = -ENOMEM;
            break;
        }

        if (htc_hdr->flags & HTC_FLG_RX_BNDL_CNT) {
            /*
             * HTC header indicates that every packet to follow
             * has the same padded length so that it can be
             * optimally fetched as a full bundle.
             */
            n_msg = (htc_hdr->flags & HTC_FLG_RX_BNDL_CNT) >>
                HTC_FLG_RX_BNDL_CNT_S;

            /* the count doesn't include the starter frame */
            n_msg++;
            if (n_msg > target->msg_per_bndl_max) {
                status = -ENOMEM;
                break;
            }

            endpoint->ep_st.rx_bundle_from_hdr += 1;
            ath6kl_dbg(ATH6KL_DBG_HTC,
                   "htc rx bundle pkts %d\n",
                   n_msg);
        } else
            /* HTC header only indicates 1 message to fetch */
            n_msg = 1;

        /* Setup packet buffers for each message */
        status = ath6kl_htc_rx_setup(target, endpoint, &lk_ahds[i],
                         queue, n_msg);

        /*
         * This is due to unavailabilty of buffers to rx entire data.
         * Return no error so that free buffers from queue can be used
         * to receive partial data.
         */
        if (status == -ENOSPC) {
            spin_unlock_bh(&target->rx_lock);
            return 0;
        }

        if (status)
            break;
    }

    spin_unlock_bh(&target->rx_lock);

    if (status) {
        list_for_each_entry_safe(packet, tmp_pkt, queue, list) {
            list_del(&packet->list);
            htc_reclaim_rxbuf(target, packet,
                      &target->endpoint[packet->endpoint]);
        }
    }

    return status;
}

static void htc_ctrl_rx(struct htc_target *context, struct htc_packet *packets)
{
    if (packets->endpoint != ENDPOINT_0) {
        WARN_ON(1);
        return;
    }

    if (packets->status == -ECANCELED) {
        reclaim_rx_ctrl_buf(context, packets);
        return;
    }

    if (packets->act_len > 0) {
        ath6kl_err("htc_ctrl_rx, got message with len:%zu\n",
               packets->act_len + HTC_HDR_LENGTH);

        ath6kl_dbg_dump(ATH6KL_DBG_HTC,
                "htc rx unexpected endpoint 0 message", "",
                packets->buf - HTC_HDR_LENGTH,
                packets->act_len + HTC_HDR_LENGTH);
    }

    htc_reclaim_rxbuf(context, packets, &context->endpoint[0]);
}

static void htc_proc_cred_rpt(struct htc_target *target,
                  struct htc_credit_report *rpt,
                  int n_entries,
                  enum htc_endpoint_id from_ep)
{
    struct htc_endpoint *endpoint;
    int tot_credits = 0, i;
    bool dist = false;

    spin_lock_bh(&target->tx_lock);

    for (i = 0; i < n_entries; i++, rpt++) {
        if (rpt->eid >= ENDPOINT_MAX) {
            WARN_ON(1);
            spin_unlock_bh(&target->tx_lock);
            return;
        }

        endpoint = &target->endpoint[rpt->eid];

        ath6kl_dbg(ATH6KL_DBG_CREDIT,
               "credit report ep %d credits %d\n",
               rpt->eid, rpt->credits);

        endpoint->ep_st.tx_cred_rpt += 1;
        endpoint->ep_st.cred_retnd += rpt->credits;

        if (from_ep == rpt->eid) {
            /*
             * This credit report arrived on the same endpoint
             * indicating it arrived in an RX packet.
             */
            endpoint->ep_st.cred_from_rx += rpt->credits;
            endpoint->ep_st.cred_rpt_from_rx += 1;
        } else if (from_ep == ENDPOINT_0) {
            /* credit arrived on endpoint 0 as a NULL message */
            endpoint->ep_st.cred_from_ep0 += rpt->credits;
            endpoint->ep_st.cred_rpt_ep0 += 1;
        } else {
            endpoint->ep_st.cred_from_other += rpt->credits;
            endpoint->ep_st.cred_rpt_from_other += 1;
        }

        if (rpt->eid == ENDPOINT_0)
            /* always give endpoint 0 credits back */
            endpoint->cred_dist.credits += rpt->credits;
        else {
            endpoint->cred_dist.cred_to_dist += rpt->credits;
            dist = true;
        }

        /*
         * Refresh tx depth for distribution function that will
         * recover these credits NOTE: this is only valid when
         * there are credits to recover!
         */
        endpoint->cred_dist.txq_depth =
            get_queue_depth(&endpoint->txq);

        tot_credits += rpt->credits;
    }

    if (dist) {
        /*
         * This was a credit return based on a completed send
         * operations note, this is done with the lock held
         */
        ath6kl_credit_distribute(target->credit_info,
                     &target->cred_dist_list,
                     HTC_CREDIT_DIST_SEND_COMPLETE);
    }

    spin_unlock_bh(&target->tx_lock);

    if (tot_credits)
        htc_chk_ep_txq(target);
}

static int htc_parse_trailer(struct htc_target *target,
                 struct htc_record_hdr *record,
                 u8 *record_buf, u32 *next_lk_ahds,
                 enum htc_endpoint_id endpoint,
                 int *n_lk_ahds)
{
    struct htc_bundle_lkahd_rpt *bundle_lkahd_rpt;
    struct htc_lookahead_report *lk_ahd;
    int len;

    switch (record->rec_id) {
    case HTC_RECORD_CREDITS:
        len = record->len / sizeof(struct htc_credit_report);
        if (!len) {
            WARN_ON(1);
            return -EINVAL;
        }

        htc_proc_cred_rpt(target,
                  (struct htc_credit_report *) record_buf,
                  len, endpoint);
        break;
    case HTC_RECORD_LOOKAHEAD:
        len = record->len / sizeof(*lk_ahd);
        if (!len) {
            WARN_ON(1);
            return -EINVAL;
        }

        lk_ahd = (struct htc_lookahead_report *) record_buf;
        if ((lk_ahd->pre_valid == ((~lk_ahd->post_valid) & 0xFF)) &&
            next_lk_ahds) {

            ath6kl_dbg(ATH6KL_DBG_HTC,
                   "htc rx lk_ahd found pre_valid 0x%x post_valid 0x%x\n",
                   lk_ahd->pre_valid, lk_ahd->post_valid);

            /* look ahead bytes are valid, copy them over */
            memcpy((u8 *)&next_lk_ahds[0], lk_ahd->lk_ahd, 4);

            ath6kl_dbg_dump(ATH6KL_DBG_HTC,
                    "htc rx next look ahead",
                    "", next_lk_ahds, 4);

            *n_lk_ahds = 1;
        }
        break;
    case HTC_RECORD_LOOKAHEAD_BUNDLE:
        len = record->len / sizeof(*bundle_lkahd_rpt);
        if (!len || (len > HTC_HOST_MAX_MSG_PER_BUNDLE)) {
            WARN_ON(1);
            return -EINVAL;
        }

        if (next_lk_ahds) {
            int i;

            bundle_lkahd_rpt =
                (struct htc_bundle_lkahd_rpt *) record_buf;

            ath6kl_dbg_dump(ATH6KL_DBG_HTC, "htc rx bundle lk_ahd",
                    "", record_buf, record->len);

            for (i = 0; i < len; i++) {
                memcpy((u8 *)&next_lk_ahds[i],
                       bundle_lkahd_rpt->lk_ahd, 4);
                bundle_lkahd_rpt++;
            }

            *n_lk_ahds = i;
        }
        break;
    default:
        ath6kl_err("unhandled record: id:%d len:%d\n",
               record->rec_id, record->len);
        break;
    }

    return 0;

}

static int htc_proc_trailer(struct htc_target *target,
                u8 *buf, int len, u32 *next_lk_ahds,
                int *n_lk_ahds, enum htc_endpoint_id endpoint)
{
    struct htc_record_hdr *record;
    int orig_len;
    int status;
    u8 *record_buf;
    u8 *orig_buf;

    ath6kl_dbg(ATH6KL_DBG_HTC, "htc rx trailer len %d\n", len);
    ath6kl_dbg_dump(ATH6KL_DBG_HTC, NULL, "", buf, len);

    orig_buf = buf;
    orig_len = len;
    status = 0;

    while (len > 0) {

        if (len < sizeof(struct htc_record_hdr)) {
            status = -ENOMEM;
            break;
        }
        /* these are byte aligned structs */
        record = (struct htc_record_hdr *) buf;
        len -= sizeof(struct htc_record_hdr);
        buf += sizeof(struct htc_record_hdr);

        if (record->len > len) {
            ath6kl_err("invalid record len: %d (id:%d) buf has: %d bytes left\n",
                   record->len, record->rec_id, len);
            status = -ENOMEM;
            break;
        }
        record_buf = buf;

        status = htc_parse_trailer(target, record, record_buf,
                       next_lk_ahds, endpoint, n_lk_ahds);

        if (status)
            break;

        /* advance buffer past this record for next time around */
        buf += record->len;
        len -= record->len;
    }

    if (status)
        ath6kl_dbg_dump(ATH6KL_DBG_HTC, "htc rx bad trailer",
                "", orig_buf, orig_len);

    return status;
}

static int ath6kl_htc_rx_process_hdr(struct htc_target *target,
                     struct htc_packet *packet,
                     u32 *next_lkahds, int *n_lkahds)
{
    int status = 0;
    u16 payload_len;
    u32 lk_ahd;
    struct htc_frame_hdr *htc_hdr = (struct htc_frame_hdr *)packet->buf;

    if (n_lkahds != NULL)
        *n_lkahds = 0;

    /*
     * NOTE: we cannot assume the alignment of buf, so we use the safe
     * macros to retrieve 16 bit fields.
     */
    payload_len = le16_to_cpu(get_unaligned(&htc_hdr->payld_len));

    memcpy((u8 *)&lk_ahd, packet->buf, sizeof(lk_ahd));

    if (packet->info.rx.rx_flags & HTC_RX_PKT_REFRESH_HDR) {
        /*
         * Refresh the expected header and the actual length as it
         * was unknown when this packet was grabbed as part of the
         * bundle.
         */
        packet->info.rx.exp_hdr = lk_ahd;
        packet->act_len = payload_len + HTC_HDR_LENGTH;

        /* validate the actual header that was refreshed  */
        if (packet->act_len > packet->buf_len) {
            ath6kl_err("refreshed hdr payload len (%d) in bundled recv is invalid (hdr: 0x%X)\n",
                   payload_len, lk_ahd);
            /*
             * Limit this to max buffer just to print out some
             * of the buffer.
             */
            packet->act_len = min(packet->act_len, packet->buf_len);
            status = -ENOMEM;
            goto fail_rx;
        }

        if (packet->endpoint != htc_hdr->eid) {
            ath6kl_err("refreshed hdr ep (%d) does not match expected ep (%d)\n",
                   htc_hdr->eid, packet->endpoint);
            status = -ENOMEM;
            goto fail_rx;
        }
    }

    if (lk_ahd != packet->info.rx.exp_hdr) {
        ath6kl_err("%s(): lk_ahd mismatch! (pPkt:0x%p flags:0x%X)\n",
               __func__, packet, packet->info.rx.rx_flags);
        ath6kl_dbg_dump(ATH6KL_DBG_HTC, "htc rx expected lk_ahd",
                "", &packet->info.rx.exp_hdr, 4);
        ath6kl_dbg_dump(ATH6KL_DBG_HTC, "htc rx current header",
                "", (u8 *)&lk_ahd, sizeof(lk_ahd));
        status = -ENOMEM;
        goto fail_rx;
    }

    if (htc_hdr->flags & HTC_FLG_RX_TRAILER) {
        if (htc_hdr->ctrl[0] < sizeof(struct htc_record_hdr) ||
            htc_hdr->ctrl[0] > payload_len) {
            ath6kl_err("%s(): invalid hdr (payload len should be :%d, CB[0] is:%d)\n",
                   __func__, payload_len, htc_hdr->ctrl[0]);
            status = -ENOMEM;
            goto fail_rx;
        }

        if (packet->info.rx.rx_flags & HTC_RX_PKT_IGNORE_LOOKAHEAD) {
            next_lkahds = NULL;
            n_lkahds = NULL;
        }

        status = htc_proc_trailer(target, packet->buf + HTC_HDR_LENGTH
                      + payload_len - htc_hdr->ctrl[0],
                      htc_hdr->ctrl[0], next_lkahds,
                       n_lkahds, packet->endpoint);

        if (status)
            goto fail_rx;

        packet->act_len -= htc_hdr->ctrl[0];
    }

    packet->buf += HTC_HDR_LENGTH;
    packet->act_len -= HTC_HDR_LENGTH;

fail_rx:
    if (status)
        ath6kl_dbg_dump(ATH6KL_DBG_HTC, "htc rx bad packet",
                "", packet->buf, packet->act_len);

    return status;
}

static void ath6kl_htc_rx_complete(struct htc_endpoint *endpoint,
                   struct htc_packet *packet)
{
        ath6kl_dbg(ATH6KL_DBG_HTC,
               "htc rx complete ep %d packet 0x%p\n",
               endpoint->eid, packet);
        endpoint->ep_cb.rx(endpoint->target, packet);
}

static int ath6kl_htc_rx_bundle(struct htc_target *target,
                struct list_head *rxq,
                struct list_head *sync_compq,
                int *n_pkt_fetched, bool part_bundle)
{
    struct hif_scatter_req *scat_req;
    struct htc_packet *packet;
    int rem_space = target->max_rx_bndl_sz;
    int n_scat_pkt, status = 0, i, len;

    n_scat_pkt = get_queue_depth(rxq);
    n_scat_pkt = min(n_scat_pkt, target->msg_per_bndl_max);

    if ((get_queue_depth(rxq) - n_scat_pkt) > 0) {
        /*
         * We were forced to split this bundle receive operation
         * all packets in this partial bundle must have their
         * lookaheads ignored.
         */
        part_bundle = true;

        /*
         * This would only happen if the target ignored our max
         * bundle limit.
         */
        ath6kl_warn("%s(): partial bundle detected num:%d , %d\n",
                __func__, get_queue_depth(rxq), n_scat_pkt);
    }

    len = 0;

    ath6kl_dbg(ATH6KL_DBG_HTC,
           "htc rx bundle depth %d pkts %d\n",
           get_queue_depth(rxq), n_scat_pkt);

    scat_req = hif_scatter_req_get(target->dev->ar);

    if (scat_req == NULL)
        goto fail_rx_pkt;

    for (i = 0; i < n_scat_pkt; i++) {
        int pad_len;

        packet = list_first_entry(rxq, struct htc_packet, list);
        list_del(&packet->list);

        pad_len = CALC_TXRX_PADDED_LEN(target,
                           packet->act_len);

        if ((rem_space - pad_len) < 0) {
            list_add(&packet->list, rxq);
            break;
        }

        rem_space -= pad_len;

        if (part_bundle || (i < (n_scat_pkt - 1)))
            /*
             * Packet 0..n-1 cannot be checked for look-aheads
             * since we are fetching a bundle the last packet
             * however can have it's lookahead used
             */
            packet->info.rx.rx_flags |=
                HTC_RX_PKT_IGNORE_LOOKAHEAD;

        /* NOTE: 1 HTC packet per scatter entry */
        scat_req->scat_list[i].buf = packet->buf;
        scat_req->scat_list[i].len = pad_len;

        packet->info.rx.rx_flags |= HTC_RX_PKT_PART_OF_BUNDLE;

        list_add_tail(&packet->list, sync_compq);

        WARN_ON(!scat_req->scat_list[i].len);
        len += scat_req->scat_list[i].len;
    }

    scat_req->len = len;
    scat_req->scat_entries = i;

    status = ath6kl_hif_submit_scat_req(target->dev, scat_req, true);

    if (!status)
        *n_pkt_fetched = i;

    /* free scatter request */
    hif_scatter_req_add(target->dev->ar, scat_req);

fail_rx_pkt:

    return status;
}

static int ath6kl_htc_rx_process_packets(struct htc_target *target,
                     struct list_head *comp_pktq,
                     u32 lk_ahds[],
                     int *n_lk_ahd)
{
    struct htc_packet *packet, *tmp_pkt;
    struct htc_endpoint *ep;
    int status = 0;

    list_for_each_entry_safe(packet, tmp_pkt, comp_pktq, list) {
        ep = &target->endpoint[packet->endpoint];

        /* process header for each of the recv packet */
        status = ath6kl_htc_rx_process_hdr(target, packet, lk_ahds,
                           n_lk_ahd);
        if (status)
            return status;

        list_del(&packet->list);

        if (list_empty(comp_pktq)) {
            /*
             * Last packet's more packet flag is set
             * based on the lookahead.
             */
            if (*n_lk_ahd > 0)
                ath6kl_htc_rx_set_indicate(lk_ahds[0],
                               ep, packet);
        } else
            /*
             * Packets in a bundle automatically have
             * this flag set.
             */
            packet->info.rx.indicat_flags |=
                HTC_RX_FLAGS_INDICATE_MORE_PKTS;

        ath6kl_htc_rx_update_stats(ep, *n_lk_ahd);

        if (packet->info.rx.rx_flags & HTC_RX_PKT_PART_OF_BUNDLE)
            ep->ep_st.rx_bundl += 1;

        ath6kl_htc_rx_complete(ep, packet);
    }

    return status;
}

static int ath6kl_htc_rx_fetch(struct htc_target *target,
                   struct list_head *rx_pktq,
                   struct list_head *comp_pktq)
{
    int fetched_pkts;
    bool part_bundle = false;
    int status = 0;
    struct list_head tmp_rxq;
    struct htc_packet *packet, *tmp_pkt;

    /* now go fetch the list of HTC packets */
    while (!list_empty(rx_pktq)) {
        fetched_pkts = 0;

        INIT_LIST_HEAD(&tmp_rxq);

        if (target->rx_bndl_enable && (get_queue_depth(rx_pktq) > 1)) {
            /*
             * There are enough packets to attempt a
             * bundle transfer and recv bundling is
             * allowed.
             */
            status = ath6kl_htc_rx_bundle(target, rx_pktq,
                              &tmp_rxq,
                              &fetched_pkts,
                              part_bundle);
            if (status)
                goto fail_rx;

            if (!list_empty(rx_pktq))
                part_bundle = true;

            list_splice_tail_init(&tmp_rxq, comp_pktq);
        }

        if (!fetched_pkts) {

            packet = list_first_entry(rx_pktq, struct htc_packet,
                           list);

            /* fully synchronous */
            packet->completion = NULL;

            if (!list_is_singular(rx_pktq))
                /*
                 * look_aheads in all packet
                 * except the last one in the
                 * bundle must be ignored
                 */
                packet->info.rx.rx_flags |=
                    HTC_RX_PKT_IGNORE_LOOKAHEAD;

            /* go fetch the packet */
            status = ath6kl_htc_rx_packet(target, packet,
                              packet->act_len);

            list_move_tail(&packet->list, &tmp_rxq);

            if (status)
                goto fail_rx;

            list_splice_tail_init(&tmp_rxq, comp_pktq);
        }
    }

    return 0;

fail_rx:

    /*
     * Cleanup any packets we allocated but didn't use to
     * actually fetch any packets.
     */

    list_for_each_entry_safe(packet, tmp_pkt, rx_pktq, list) {
        list_del(&packet->list);
        htc_reclaim_rxbuf(target, packet,
                  &target->endpoint[packet->endpoint]);
    }

    list_for_each_entry_safe(packet, tmp_pkt, &tmp_rxq, list) {
        list_del(&packet->list);
        htc_reclaim_rxbuf(target, packet,
                  &target->endpoint[packet->endpoint]);
    }

    return status;
}

int ath6kl_htc_rxmsg_pending_handler(struct htc_target *target,
                     u32 msg_look_ahead, int *num_pkts)
{
    struct htc_packet *packets, *tmp_pkt;
    struct htc_endpoint *endpoint;
    struct list_head rx_pktq, comp_pktq;
    int status = 0;
    u32 look_aheads[HTC_HOST_MAX_MSG_PER_BUNDLE];
    int num_look_ahead = 1;
    enum htc_endpoint_id id;
    int n_fetched = 0;

    INIT_LIST_HEAD(&comp_pktq);
    *num_pkts = 0;

    /*
     * On first entry copy the look_aheads into our temp array for
     * processing
     */
    look_aheads[0] = msg_look_ahead;

    while (true) {

        /*
         * First lookahead sets the expected endpoint IDs for all
         * packets in a bundle.
         */
        id = ((struct htc_frame_hdr *)&look_aheads[0])->eid;
        endpoint = &target->endpoint[id];

        if (id >= ENDPOINT_MAX) {
            ath6kl_err("MsgPend, invalid endpoint in look-ahead: %d\n",
                   id);
            status = -ENOMEM;
            break;
        }

        INIT_LIST_HEAD(&rx_pktq);
        INIT_LIST_HEAD(&comp_pktq);

        /*
         * Try to allocate as many HTC RX packets indicated by the
         * look_aheads.
         */
        status = ath6kl_htc_rx_alloc(target, look_aheads,
                         num_look_ahead, endpoint,
                         &rx_pktq);
        if (status)
            break;

        if (get_queue_depth(&rx_pktq) >= 2)
            /*
             * A recv bundle was detected, force IRQ status
             * re-check again
             */
            target->chk_irq_status_cnt = 1;

        n_fetched += get_queue_depth(&rx_pktq);

        num_look_ahead = 0;

        status = ath6kl_htc_rx_fetch(target, &rx_pktq, &comp_pktq);

        if (!status)
            ath6kl_htc_rx_chk_water_mark(endpoint);

        /* Process fetched packets */
        status = ath6kl_htc_rx_process_packets(target, &comp_pktq,
                               look_aheads,
                               &num_look_ahead);

        if (!num_look_ahead || status)
            break;

        /*
         * For SYNCH processing, if we get here, we are running
         * through the loop again due to a detected lookahead. Set
         * flag that we should re-check IRQ status registers again
         * before leaving IRQ processing, this can net better
         * performance in high throughput situations.
         */
        target->chk_irq_status_cnt = 1;
    }

    if (status) {
        ath6kl_err("failed to get pending recv messages: %d\n",
               status);

        /* cleanup any packets in sync completion queue */
        list_for_each_entry_safe(packets, tmp_pkt, &comp_pktq, list) {
            list_del(&packets->list);
            htc_reclaim_rxbuf(target, packets,
                      &target->endpoint[packets->endpoint]);
        }

        if (target->htc_flags & HTC_OP_STATE_STOPPING) {
            ath6kl_warn("host is going to stop blocking receiver for htc_stop\n");
            ath6kl_hif_rx_control(target->dev, false);
        }
    }

    /*
     * Before leaving, check to see if host ran out of buffers and
     * needs to stop the receiver.
     */
    if (target->rx_st_flags & HTC_RECV_WAIT_BUFFERS) {
        ath6kl_warn("host has no rx buffers blocking receiver to prevent overrun\n");
        ath6kl_hif_rx_control(target->dev, false);
    }
    *num_pkts = n_fetched;

    return status;
}

/*
 * Synchronously wait for a control message from the target,
 * This function is used at initialization time ONLY.  At init messages
 * on ENDPOINT 0 are expected.
 */
static struct htc_packet *htc_wait_for_ctrl_msg(struct htc_target *target)
{
    struct htc_packet *packet = NULL;
    struct htc_frame_hdr *htc_hdr;
    u32 look_ahead;

    if (ath6kl_hif_poll_mboxmsg_rx(target->dev, &look_ahead,
                       HTC_TARGET_RESPONSE_TIMEOUT))
        return NULL;

    ath6kl_dbg(ATH6KL_DBG_HTC,
           "htc rx wait ctrl look_ahead 0x%X\n", look_ahead);

    htc_hdr = (struct htc_frame_hdr *)&look_ahead;

    if (htc_hdr->eid != ENDPOINT_0)
        return NULL;

    packet = htc_get_control_buf(target, false);

    if (!packet)
        return NULL;

    packet->info.rx.rx_flags = 0;
    packet->info.rx.exp_hdr = look_ahead;
    packet->act_len = le16_to_cpu(htc_hdr->payld_len) + HTC_HDR_LENGTH;

    if (packet->act_len > packet->buf_len)
        goto fail_ctrl_rx;

    /* we want synchronous operation */
    packet->completion = NULL;

    /* get the message from the device, this will block */
    if (ath6kl_htc_rx_packet(target, packet, packet->act_len))
        goto fail_ctrl_rx;

    /* process receive header */
    packet->status = ath6kl_htc_rx_process_hdr(target, packet, NULL, NULL);

    if (packet->status) {
        ath6kl_err("htc_wait_for_ctrl_msg, ath6kl_htc_rx_process_hdr failed (status = %d)\n",
               packet->status);
        goto fail_ctrl_rx;
    }

    return packet;

fail_ctrl_rx:
    if (packet != NULL) {
        htc_rxpkt_reset(packet);
        reclaim_rx_ctrl_buf(target, packet);
    }

    return NULL;
}

static int ath6kl_htc_mbox_add_rxbuf_multiple(struct htc_target *target,
                  struct list_head *pkt_queue)
{
    struct htc_endpoint *endpoint;
    struct htc_packet *first_pkt;
    bool rx_unblock = false;
    int status = 0, depth;

    if (list_empty(pkt_queue))
        return -ENOMEM;

    first_pkt = list_first_entry(pkt_queue, struct htc_packet, list);

    if (first_pkt->endpoint >= ENDPOINT_MAX)
        return status;

    depth = get_queue_depth(pkt_queue);

    ath6kl_dbg(ATH6KL_DBG_HTC,
           "htc rx add multiple ep id %d cnt %d len %d\n",
        first_pkt->endpoint, depth, first_pkt->buf_len);

    endpoint = &target->endpoint[first_pkt->endpoint];

    if (target->htc_flags & HTC_OP_STATE_STOPPING) {
        struct htc_packet *packet, *tmp_pkt;

        /* walk through queue and mark each one canceled */
        list_for_each_entry_safe(packet, tmp_pkt, pkt_queue, list) {
            packet->status = -ECANCELED;
            list_del(&packet->list);
            ath6kl_htc_rx_complete(endpoint, packet);
        }

        return status;
    }

    spin_lock_bh(&target->rx_lock);

    list_splice_tail_init(pkt_queue, &endpoint->rx_bufq);

    /* check if we are blocked waiting for a new buffer */
    if (target->rx_st_flags & HTC_RECV_WAIT_BUFFERS) {
        if (target->ep_waiting == first_pkt->endpoint) {
            ath6kl_dbg(ATH6KL_DBG_HTC,
                   "htc rx blocked on ep %d, unblocking\n",
                   target->ep_waiting);
            target->rx_st_flags &= ~HTC_RECV_WAIT_BUFFERS;
            target->ep_waiting = ENDPOINT_MAX;
            rx_unblock = true;
        }
    }

    spin_unlock_bh(&target->rx_lock);

    if (rx_unblock && !(target->htc_flags & HTC_OP_STATE_STOPPING))
        /* TODO : implement a buffer threshold count? */
        ath6kl_hif_rx_control(target->dev, true);

    return status;
}

static void ath6kl_htc_mbox_flush_rx_buf(struct htc_target *target)
{
    struct htc_endpoint *endpoint;
    struct htc_packet *packet, *tmp_pkt;
    int i;

    for (i = ENDPOINT_0; i < ENDPOINT_MAX; i++) {
        endpoint = &target->endpoint[i];
        if (!endpoint->svc_id)
            /* not in use.. */
            continue;

        spin_lock_bh(&target->rx_lock);
        list_for_each_entry_safe(packet, tmp_pkt,
                     &endpoint->rx_bufq, list) {
            list_del(&packet->list);
            spin_unlock_bh(&target->rx_lock);
            ath6kl_dbg(ATH6KL_DBG_HTC,
                   "htc rx flush pkt 0x%p  len %d  ep %d\n",
                   packet, packet->buf_len,
                   packet->endpoint);
            /*
             * packets in rx_bufq of endpoint 0 have originally
             * been queued from target->free_ctrl_rxbuf where
             * packet and packet->buf_start are allocated
             * separately using kmalloc(). For other endpoint
             * rx_bufq, it is allocated as skb where packet is
             * skb->head. Take care of this difference while freeing
             * the memory.
             */
            if (packet->endpoint == ENDPOINT_0) {
                kfree(packet->buf_start);
                kfree(packet);
            } else {
                dev_kfree_skb(packet->pkt_cntxt);
            }
            spin_lock_bh(&target->rx_lock);
        }
        spin_unlock_bh(&target->rx_lock);
    }
}

static int ath6kl_htc_mbox_conn_service(struct htc_target *target,
                struct htc_service_connect_req *conn_req,
                struct htc_service_connect_resp *conn_resp)
{
    struct htc_packet *rx_pkt = NULL;
    struct htc_packet *tx_pkt = NULL;
    struct htc_conn_service_resp *resp_msg;
    struct htc_conn_service_msg *conn_msg;
    struct htc_endpoint *endpoint;
    enum htc_endpoint_id assigned_ep = ENDPOINT_MAX;
    unsigned int max_msg_sz = 0;
    int status = 0;
    u16 msg_id;

    ath6kl_dbg(ATH6KL_DBG_HTC,
           "htc connect service target 0x%p service id 0x%x\n",
           target, conn_req->svc_id);

    if (conn_req->svc_id == HTC_CTRL_RSVD_SVC) {
        /* special case for pseudo control service */
        assigned_ep = ENDPOINT_0;
        max_msg_sz = HTC_MAX_CTRL_MSG_LEN;
    } else {
        /* allocate a packet to send to the target */
        tx_pkt = htc_get_control_buf(target, true);

        if (!tx_pkt)
            return -ENOMEM;

        conn_msg = (struct htc_conn_service_msg *)tx_pkt->buf;
        memset(conn_msg, 0, sizeof(*conn_msg));
        conn_msg->msg_id = cpu_to_le16(HTC_MSG_CONN_SVC_ID);
        conn_msg->svc_id = cpu_to_le16(conn_req->svc_id);
        conn_msg->conn_flags = cpu_to_le16(conn_req->conn_flags);

        set_htc_pkt_info(tx_pkt, NULL, (u8 *) conn_msg,
                 sizeof(*conn_msg) + conn_msg->svc_meta_len,
                 ENDPOINT_0, HTC_SERVICE_TX_PACKET_TAG);

        /* we want synchronous operation */
        tx_pkt->completion = NULL;
        ath6kl_htc_tx_prep_pkt(tx_pkt, 0, 0, 0);
        status = ath6kl_htc_tx_issue(target, tx_pkt);

        if (status)
            goto fail_tx;

        /* wait for response */
        rx_pkt = htc_wait_for_ctrl_msg(target);

        if (!rx_pkt) {
            status = -ENOMEM;
            goto fail_tx;
        }

        resp_msg = (struct htc_conn_service_resp *)rx_pkt->buf;
        msg_id = le16_to_cpu(resp_msg->msg_id);

        if ((msg_id != HTC_MSG_CONN_SVC_RESP_ID) ||
            (rx_pkt->act_len < sizeof(*resp_msg))) {
            status = -ENOMEM;
            goto fail_tx;
        }

        conn_resp->resp_code = resp_msg->status;
        /* check response status */
        if (resp_msg->status != HTC_SERVICE_SUCCESS) {
            ath6kl_err("target failed service 0x%X connect request (status:%d)\n",
                   resp_msg->svc_id, resp_msg->status);
            status = -ENOMEM;
            goto fail_tx;
        }

        assigned_ep = (enum htc_endpoint_id)resp_msg->eid;
        max_msg_sz = le16_to_cpu(resp_msg->max_msg_sz);
    }

    if (assigned_ep >= ENDPOINT_MAX || !max_msg_sz) {
        status = -ENOMEM;
        goto fail_tx;
    }

    endpoint = &target->endpoint[assigned_ep];
    endpoint->eid = assigned_ep;
    if (endpoint->svc_id) {
        status = -ENOMEM;
        goto fail_tx;
    }

    /* return assigned endpoint to caller */
    conn_resp->endpoint = assigned_ep;
    conn_resp->len_max = max_msg_sz;

    /* setup the endpoint */

    /* this marks the endpoint in use */
    endpoint->svc_id = conn_req->svc_id;

    endpoint->max_txq_depth = conn_req->max_txq_depth;
    endpoint->len_max = max_msg_sz;
    endpoint->ep_cb = conn_req->ep_cb;
    endpoint->cred_dist.svc_id = conn_req->svc_id;
    endpoint->cred_dist.htc_ep = endpoint;
    endpoint->cred_dist.endpoint = assigned_ep;
    endpoint->cred_dist.cred_sz = target->tgt_cred_sz;

    switch (endpoint->svc_id) {
    case WMI_DATA_BK_SVC:
        endpoint->tx_drop_packet_threshold = MAX_DEF_COOKIE_NUM / 3;
        break;
    default:
        endpoint->tx_drop_packet_threshold = MAX_HI_COOKIE_NUM;
        break;
    }

    if (conn_req->max_rxmsg_sz) {
        /*
         * Override cred_per_msg calculation, this optimizes
         * the credit-low indications since the host will actually
         * issue smaller messages in the Send path.
         */
        if (conn_req->max_rxmsg_sz > max_msg_sz) {
            status = -ENOMEM;
            goto fail_tx;
        }
        endpoint->cred_dist.cred_per_msg =
            conn_req->max_rxmsg_sz / target->tgt_cred_sz;
    } else
        endpoint->cred_dist.cred_per_msg =
            max_msg_sz / target->tgt_cred_sz;

    if (!endpoint->cred_dist.cred_per_msg)
        endpoint->cred_dist.cred_per_msg = 1;

    /* save local connection flags */
    endpoint->conn_flags = conn_req->flags;

fail_tx:
    if (tx_pkt)
        htc_reclaim_txctrl_buf(target, tx_pkt);

    if (rx_pkt) {
        htc_rxpkt_reset(rx_pkt);
        reclaim_rx_ctrl_buf(target, rx_pkt);
    }

    return status;
}

static void reset_ep_state(struct htc_target *target)
{
    struct htc_endpoint *endpoint;
    int i;

    for (i = ENDPOINT_0; i < ENDPOINT_MAX; i++) {
        endpoint = &target->endpoint[i];
        memset(&endpoint->cred_dist, 0, sizeof(endpoint->cred_dist));
        endpoint->svc_id = 0;
        endpoint->len_max = 0;
        endpoint->max_txq_depth = 0;
        memset(&endpoint->ep_st, 0,
               sizeof(endpoint->ep_st));
        INIT_LIST_HEAD(&endpoint->rx_bufq);
        INIT_LIST_HEAD(&endpoint->txq);
        endpoint->target = target;
    }

    /* reset distribution list */
    /* FIXME: free existing entries */
    INIT_LIST_HEAD(&target->cred_dist_list);
}

static int ath6kl_htc_mbox_get_rxbuf_num(struct htc_target *target,
                 enum htc_endpoint_id endpoint)
{
    int num;

    spin_lock_bh(&target->rx_lock);
    num = get_queue_depth(&(target->endpoint[endpoint].rx_bufq));
    spin_unlock_bh(&target->rx_lock);
    return num;
}

static void htc_setup_msg_bndl(struct htc_target *target)
{
    /* limit what HTC can handle */
    target->msg_per_bndl_max = min(HTC_HOST_MAX_MSG_PER_BUNDLE,
                       target->msg_per_bndl_max);

    if (ath6kl_hif_enable_scatter(target->dev->ar)) {
        target->msg_per_bndl_max = 0;
        return;
    }

    /* limit bundle what the device layer can handle */
    target->msg_per_bndl_max = min(target->max_scat_entries,
                       target->msg_per_bndl_max);

    ath6kl_dbg(ATH6KL_DBG_BOOT,
           "htc bundling allowed msg_per_bndl_max %d\n",
           target->msg_per_bndl_max);

    /* Max rx bundle size is limited by the max tx bundle size */
    target->max_rx_bndl_sz = target->max_xfer_szper_scatreq;
    /* Max tx bundle size if limited by the extended mbox address range */
    target->max_tx_bndl_sz = min(HIF_MBOX0_EXT_WIDTH,
                     target->max_xfer_szper_scatreq);

    ath6kl_dbg(ATH6KL_DBG_BOOT, "htc max_rx_bndl_sz %d max_tx_bndl_sz %d\n",
           target->max_rx_bndl_sz, target->max_tx_bndl_sz);

    if (target->max_tx_bndl_sz)
        /* tx_bndl_mask is enabled per AC, each has 1 bit */
        target->tx_bndl_mask = (1 << WMM_NUM_AC) - 1;

    if (target->max_rx_bndl_sz)
        target->rx_bndl_enable = true;

    if ((target->tgt_cred_sz % target->block_sz) != 0) {
        ath6kl_warn("credit size: %d is not block aligned! Disabling send bundling\n",
                target->tgt_cred_sz);

        /*
         * Disallow send bundling since the credit size is
         * not aligned to a block size the I/O block
         * padding will spill into the next credit buffer
         * which is fatal.
         */
        target->tx_bndl_mask = 0;
    }
}

static int ath6kl_htc_mbox_wait_target(struct htc_target *target)
{
    struct htc_packet *packet = NULL;
    struct htc_ready_ext_msg *rdy_msg;
    struct htc_service_connect_req connect;
    struct htc_service_connect_resp resp;
    int status;

    /* FIXME: remove once USB support is implemented */
    if (target->dev->ar->hif_type == ATH6KL_HIF_TYPE_USB) {
        ath6kl_err("HTC doesn't support USB yet. Patience!\n");
        return -EOPNOTSUPP;
    }

    /* we should be getting 1 control message that the target is ready */
    packet = htc_wait_for_ctrl_msg(target);

    if (!packet)
        return -ENOMEM;

    /* we controlled the buffer creation so it's properly aligned */
    rdy_msg = (struct htc_ready_ext_msg *)packet->buf;

    if ((le16_to_cpu(rdy_msg->ver2_0_info.msg_id) != HTC_MSG_READY_ID) ||
        (packet->act_len < sizeof(struct htc_ready_msg))) {
        status = -ENOMEM;
        goto fail_wait_target;
    }

    if (!rdy_msg->ver2_0_info.cred_cnt || !rdy_msg->ver2_0_info.cred_sz) {
        status = -ENOMEM;
        goto fail_wait_target;
    }

    target->tgt_creds = le16_to_cpu(rdy_msg->ver2_0_info.cred_cnt);
    target->tgt_cred_sz = le16_to_cpu(rdy_msg->ver2_0_info.cred_sz);

    ath6kl_dbg(ATH6KL_DBG_BOOT,
           "htc target ready credits %d size %d\n",
           target->tgt_creds, target->tgt_cred_sz);

    /* check if this is an extended ready message */
    if (packet->act_len >= sizeof(struct htc_ready_ext_msg)) {
        /* this is an extended message */
        target->htc_tgt_ver = rdy_msg->htc_ver;
        target->msg_per_bndl_max = rdy_msg->msg_per_htc_bndl;
    } else {
        /* legacy */
        target->htc_tgt_ver = HTC_VERSION_2P0;
        target->msg_per_bndl_max = 0;
    }

    ath6kl_dbg(ATH6KL_DBG_BOOT, "htc using protocol %s (%d)\n",
           (target->htc_tgt_ver == HTC_VERSION_2P0) ? "2.0" : ">= 2.1",
           target->htc_tgt_ver);

    if (target->msg_per_bndl_max > 0)
        htc_setup_msg_bndl(target);

    /* setup our pseudo HTC control endpoint connection */
    memset(&connect, 0, sizeof(connect));
    memset(&resp, 0, sizeof(resp));
    connect.ep_cb.rx = htc_ctrl_rx;
    connect.ep_cb.rx_refill = NULL;
    connect.ep_cb.tx_full = NULL;
    connect.max_txq_depth = NUM_CONTROL_BUFFERS;
    connect.svc_id = HTC_CTRL_RSVD_SVC;

    /* connect fake service */
    status = ath6kl_htc_mbox_conn_service((void *)target, &connect, &resp);

    if (status)
        /*
         * FIXME: this call doesn't make sense, the caller should
         * call ath6kl_htc_mbox_cleanup() when it wants remove htc
         */
        ath6kl_hif_cleanup_scatter(target->dev->ar);

fail_wait_target:
    if (packet) {
        htc_rxpkt_reset(packet);
        reclaim_rx_ctrl_buf(target, packet);
    }

    return status;
}

/*
 * Start HTC, enable interrupts and let the target know
 * host has finished setup.
 */
static int ath6kl_htc_mbox_start(struct htc_target *target)
{
    struct htc_packet *packet;
    int status;

    memset(&target->dev->irq_proc_reg, 0,
           sizeof(target->dev->irq_proc_reg));

    /* Disable interrupts at the chip level */
    ath6kl_hif_disable_intrs(target->dev);

    target->htc_flags = 0;
    target->rx_st_flags = 0;

    /* Push control receive buffers into htc control endpoint */
    while ((packet = htc_get_control_buf(target, false)) != NULL) {
        status = htc_add_rxbuf(target, packet);
        if (status)
            return status;
    }

    /* NOTE: the first entry in the distribution list is ENDPOINT_0 */
    ath6kl_credit_init(target->credit_info, &target->cred_dist_list,
               target->tgt_creds);

    dump_cred_dist_stats(target);

    /* Indicate to the target of the setup completion */
    status = htc_setup_tx_complete(target);

    if (status)
        return status;

    /* unmask interrupts */
    status = ath6kl_hif_unmask_intrs(target->dev);

    if (status)
        ath6kl_htc_mbox_stop(target);

    return status;
}

static int ath6kl_htc_reset(struct htc_target *target)
{
    u32 block_size, ctrl_bufsz;
    struct htc_packet *packet;
    int i;

    reset_ep_state(target);

    block_size = target->dev->ar->mbox_info.block_size;

    ctrl_bufsz = (block_size > HTC_MAX_CTRL_MSG_LEN) ?
              (block_size + HTC_HDR_LENGTH) :
              (HTC_MAX_CTRL_MSG_LEN + HTC_HDR_LENGTH);

    for (i = 0; i < NUM_CONTROL_BUFFERS; i++) {
        packet = kzalloc(sizeof(*packet), GFP_KERNEL);
        if (!packet)
            return -ENOMEM;

        packet->buf_start = kzalloc(ctrl_bufsz, GFP_KERNEL);
        if (!packet->buf_start) {
            kfree(packet);
            return -ENOMEM;
        }

        packet->buf_len = ctrl_bufsz;
        if (i < NUM_CONTROL_RX_BUFFERS) {
            packet->act_len = 0;
            packet->buf = packet->buf_start;
            packet->endpoint = ENDPOINT_0;
            list_add_tail(&packet->list, &target->free_ctrl_rxbuf);
        } else
            list_add_tail(&packet->list, &target->free_ctrl_txbuf);
    }

    return 0;
}

/* htc_stop: stop interrupt reception, and flush all queued buffers */
static void ath6kl_htc_mbox_stop(struct htc_target *target)
{
    spin_lock_bh(&target->htc_lock);
    target->htc_flags |= HTC_OP_STATE_STOPPING;
    spin_unlock_bh(&target->htc_lock);

    /*
     * Masking interrupts is a synchronous operation, when this
     * function returns all pending HIF I/O has completed, we can
     * safely flush the queues.
     */
    ath6kl_hif_mask_intrs(target->dev);

    ath6kl_htc_flush_txep_all(target);

    ath6kl_htc_mbox_flush_rx_buf(target);

    ath6kl_htc_reset(target);
}

static void *ath6kl_htc_mbox_create(struct ath6kl *ar)
{
    struct htc_target *target = NULL;
    int status = 0;

    target = kzalloc(sizeof(*target), GFP_KERNEL);
    if (!target) {
        ath6kl_err("unable to allocate memory\n");
        return NULL;
    }

    target->dev = kzalloc(sizeof(*target->dev), GFP_KERNEL);
    if (!target->dev) {
        ath6kl_err("unable to allocate memory\n");
        status = -ENOMEM;
        goto err_htc_cleanup;
    }

    spin_lock_init(&target->htc_lock);
    spin_lock_init(&target->rx_lock);
    spin_lock_init(&target->tx_lock);

    INIT_LIST_HEAD(&target->free_ctrl_txbuf);
    INIT_LIST_HEAD(&target->free_ctrl_rxbuf);
    INIT_LIST_HEAD(&target->cred_dist_list);

    target->dev->ar = ar;
    target->dev->htc_cnxt = target;
    target->ep_waiting = ENDPOINT_MAX;

    status = ath6kl_hif_setup(target->dev);
    if (status)
        goto err_htc_cleanup;

    status = ath6kl_htc_reset(target);
    if (status)
        goto err_htc_cleanup;

    return target;

err_htc_cleanup:
    ath6kl_htc_mbox_cleanup(target);

    return NULL;
}

/* cleanup the HTC instance */
static void ath6kl_htc_mbox_cleanup(struct htc_target *target)
{
    struct htc_packet *packet, *tmp_packet;

    /* FIXME: remove check once USB support is implemented */
    if (target->dev->ar->hif_type != ATH6KL_HIF_TYPE_USB)
        ath6kl_hif_cleanup_scatter(target->dev->ar);

    list_for_each_entry_safe(packet, tmp_packet,
                 &target->free_ctrl_txbuf, list) {
        list_del(&packet->list);
        kfree(packet->buf_start);
        kfree(packet);
    }

    list_for_each_entry_safe(packet, tmp_packet,
                 &target->free_ctrl_rxbuf, list) {
        list_del(&packet->list);
        kfree(packet->buf_start);
        kfree(packet);
    }

    kfree(target->dev);
    kfree(target);
}

static const struct ath6kl_htc_ops ath6kl_htc_mbox_ops = {
    .create = ath6kl_htc_mbox_create,
    .wait_target = ath6kl_htc_mbox_wait_target,
    .start = ath6kl_htc_mbox_start,
    .conn_service = ath6kl_htc_mbox_conn_service,
    .tx = ath6kl_htc_mbox_tx,
    .stop = ath6kl_htc_mbox_stop,
    .cleanup = ath6kl_htc_mbox_cleanup,
    .flush_txep = ath6kl_htc_mbox_flush_txep,
    .flush_rx_buf = ath6kl_htc_mbox_flush_rx_buf,
    .activity_changed = ath6kl_htc_mbox_activity_changed,
    .get_rxbuf_num = ath6kl_htc_mbox_get_rxbuf_num,
    .add_rxbuf_multiple = ath6kl_htc_mbox_add_rxbuf_multiple,
    .credit_setup = ath6kl_htc_mbox_credit_setup,
};

void ath6kl_htc_mbox_attach(struct ath6kl *ar)
{
    ar->htc_ops = &ath6kl_htc_mbox_ops;
}