qib_user_sdma.c

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/*
 * Copyright (c) 2007, 2008, 2009 QLogic Corporation. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#include <linux/mm.h>
#include <linux/types.h>
#include <linux/device.h>
#include <linux/dmapool.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/highmem.h>
#include <linux/io.h>
#include <linux/uio.h>
#include <linux/rbtree.h>
#include <linux/spinlock.h>
#include <linux/delay.h>

#include "qib.h"
#include "qib_user_sdma.h"

/* minimum size of header */
#define QIB_USER_SDMA_MIN_HEADER_LENGTH 64
/* expected size of headers (for dma_pool) */
#define QIB_USER_SDMA_EXP_HEADER_LENGTH 64
/* attempt to drain the queue for 5secs */
#define QIB_USER_SDMA_DRAIN_TIMEOUT 500

struct qib_user_sdma_pkt {
    u8 naddr;               /* dimension of addr (1..3) ... */
    u32 counter;            /* sdma pkts queued counter for this entry */
    u64 added;              /* global descq number of entries */

    struct {
        u32 offset;                     /* offset for kvaddr, addr */
        u32 length;                     /* length in page */
        u8  put_page;                   /* should we put_page? */
        u8  dma_mapped;                 /* is page dma_mapped? */
        struct page *page;              /* may be NULL (coherent mem) */
        void *kvaddr;                   /* FIXME: only for pio hack */
        dma_addr_t addr;
    } addr[4];   /* max pages, any more and we coalesce */
    struct list_head list;  /* list element */
};

struct qib_user_sdma_queue {
    /*
     * pkts sent to dma engine are queued on this
     * list head.  the type of the elements of this
     * list are struct qib_user_sdma_pkt...
     */
    struct list_head sent;

    /* headers with expected length are allocated from here... */
    char header_cache_name[64];
    struct dma_pool *header_cache;

    /* packets are allocated from the slab cache... */
    char pkt_slab_name[64];
    struct kmem_cache *pkt_slab;

    /* as packets go on the queued queue, they are counted... */
    u32 counter;
    u32 sent_counter;

    /* dma page table */
    struct rb_root dma_pages_root;

    /* protect everything above... */
    struct mutex lock;
};

struct qib_user_sdma_queue *
qib_user_sdma_queue_create(struct device *dev, int unit, int ctxt, int sctxt)
{
    struct qib_user_sdma_queue *pq =
        kmalloc(sizeof(struct qib_user_sdma_queue), GFP_KERNEL);

    if (!pq)
        goto done;

    pq->counter = 0;
    pq->sent_counter = 0;
    INIT_LIST_HEAD(&pq->sent);

    mutex_init(&pq->lock);

    snprintf(pq->pkt_slab_name, sizeof(pq->pkt_slab_name),
         "qib-user-sdma-pkts-%u-%02u.%02u", unit, ctxt, sctxt);
    pq->pkt_slab = kmem_cache_create(pq->pkt_slab_name,
                     sizeof(struct qib_user_sdma_pkt),
                     0, 0, NULL);

    if (!pq->pkt_slab)
        goto err_kfree;

    snprintf(pq->header_cache_name, sizeof(pq->header_cache_name),
         "qib-user-sdma-headers-%u-%02u.%02u", unit, ctxt, sctxt);
    pq->header_cache = dma_pool_create(pq->header_cache_name,
                       dev,
                       QIB_USER_SDMA_EXP_HEADER_LENGTH,
                       4, 0);
    if (!pq->header_cache)
        goto err_slab;

    pq->dma_pages_root = RB_ROOT;

    goto done;

err_slab:
    kmem_cache_destroy(pq->pkt_slab);
err_kfree:
    kfree(pq);
    pq = NULL;

done:
    return pq;
}

static void qib_user_sdma_init_frag(struct qib_user_sdma_pkt *pkt,
                    int i, size_t offset, size_t len,
                    int put_page, int dma_mapped,
                    struct page *page,
                    void *kvaddr, dma_addr_t dma_addr)
{
    pkt->addr[i].offset = offset;
    pkt->addr[i].length = len;
    pkt->addr[i].put_page = put_page;
    pkt->addr[i].dma_mapped = dma_mapped;
    pkt->addr[i].page = page;
    pkt->addr[i].kvaddr = kvaddr;
    pkt->addr[i].addr = dma_addr;
}

static void qib_user_sdma_init_header(struct qib_user_sdma_pkt *pkt,
                      u32 counter, size_t offset,
                      size_t len, int dma_mapped,
                      struct page *page,
                      void *kvaddr, dma_addr_t dma_addr)
{
    pkt->naddr = 1;
    pkt->counter = counter;
    qib_user_sdma_init_frag(pkt, 0, offset, len, 0, dma_mapped, page,
                kvaddr, dma_addr);
}

/* we've too many pages in the iovec, coalesce to a single page */
static int qib_user_sdma_coalesce(const struct qib_devdata *dd,
                  struct qib_user_sdma_pkt *pkt,
                  const struct iovec *iov,
                  unsigned long niov)
{
    int ret = 0;
    struct page *page = alloc_page(GFP_KERNEL);
    void *mpage_save;
    char *mpage;
    int i;
    int len = 0;
    dma_addr_t dma_addr;

    if (!page) {
        ret = -ENOMEM;
        goto done;
    }

    mpage = kmap(page);
    mpage_save = mpage;
    for (i = 0; i < niov; i++) {
        int cfur;

        cfur = copy_from_user(mpage,
                      iov[i].iov_base, iov[i].iov_len);
        if (cfur) {
            ret = -EFAULT;
            goto free_unmap;
        }

        mpage += iov[i].iov_len;
        len += iov[i].iov_len;
    }

    dma_addr = dma_map_page(&dd->pcidev->dev, page, 0, len,
                DMA_TO_DEVICE);
    if (dma_mapping_error(&dd->pcidev->dev, dma_addr)) {
        ret = -ENOMEM;
        goto free_unmap;
    }

    qib_user_sdma_init_frag(pkt, 1, 0, len, 0, 1, page, mpage_save,
                dma_addr);
    pkt->naddr = 2;

    goto done;

free_unmap:
    kunmap(page);
    __free_page(page);
done:
    return ret;
}

/*
 * How many pages in this iovec element?
 */
static int qib_user_sdma_num_pages(const struct iovec *iov)
{
    const unsigned long addr  = (unsigned long) iov->iov_base;
    const unsigned long  len  = iov->iov_len;
    const unsigned long spage = addr & PAGE_MASK;
    const unsigned long epage = (addr + len - 1) & PAGE_MASK;

    return 1 + ((epage - spage) >> PAGE_SHIFT);
}

/*
 * Truncate length to page boundary.
 */
static int qib_user_sdma_page_length(unsigned long addr, unsigned long len)
{
    const unsigned long offset = addr & ~PAGE_MASK;

    return ((offset + len) > PAGE_SIZE) ? (PAGE_SIZE - offset) : len;
}

static void qib_user_sdma_free_pkt_frag(struct device *dev,
                    struct qib_user_sdma_queue *pq,
                    struct qib_user_sdma_pkt *pkt,
                    int frag)
{
    const int i = frag;

    if (pkt->addr[i].page) {
        if (pkt->addr[i].dma_mapped)
            dma_unmap_page(dev,
                       pkt->addr[i].addr,
                       pkt->addr[i].length,
                       DMA_TO_DEVICE);

        if (pkt->addr[i].kvaddr)
            kunmap(pkt->addr[i].page);

        if (pkt->addr[i].put_page)
            put_page(pkt->addr[i].page);
        else
            __free_page(pkt->addr[i].page);
    } else if (pkt->addr[i].kvaddr)
        /* free coherent mem from cache... */
        dma_pool_free(pq->header_cache,
                  pkt->addr[i].kvaddr, pkt->addr[i].addr);
}

/* return number of pages pinned... */
static int qib_user_sdma_pin_pages(const struct qib_devdata *dd,
                   struct qib_user_sdma_pkt *pkt,
                   unsigned long addr, int tlen, int npages)
{
    struct page *pages[2];
    int j;
    int ret;

    ret = get_user_pages(current, current->mm, addr,
                 npages, 0, 1, pages, NULL);

    if (ret != npages) {
        int i;

        for (i = 0; i < ret; i++)
            put_page(pages[i]);

        ret = -ENOMEM;
        goto done;
    }

    for (j = 0; j < npages; j++) {
        /* map the pages... */
        const int flen = qib_user_sdma_page_length(addr, tlen);
        dma_addr_t dma_addr =
            dma_map_page(&dd->pcidev->dev,
                     pages[j], 0, flen, DMA_TO_DEVICE);
        unsigned long fofs = addr & ~PAGE_MASK;

        if (dma_mapping_error(&dd->pcidev->dev, dma_addr)) {
            ret = -ENOMEM;
            goto done;
        }

        qib_user_sdma_init_frag(pkt, pkt->naddr, fofs, flen, 1, 1,
                    pages[j], kmap(pages[j]), dma_addr);

        pkt->naddr++;
        addr += flen;
        tlen -= flen;
    }

done:
    return ret;
}

static int qib_user_sdma_pin_pkt(const struct qib_devdata *dd,
                 struct qib_user_sdma_queue *pq,
                 struct qib_user_sdma_pkt *pkt,
                 const struct iovec *iov,
                 unsigned long niov)
{
    int ret = 0;
    unsigned long idx;

    for (idx = 0; idx < niov; idx++) {
        const int npages = qib_user_sdma_num_pages(iov + idx);
        const unsigned long addr = (unsigned long) iov[idx].iov_base;

        ret = qib_user_sdma_pin_pages(dd, pkt, addr,
                          iov[idx].iov_len, npages);
        if (ret < 0)
            goto free_pkt;
    }

    goto done;

free_pkt:
    for (idx = 0; idx < pkt->naddr; idx++)
        qib_user_sdma_free_pkt_frag(&dd->pcidev->dev, pq, pkt, idx);

done:
    return ret;
}

static int qib_user_sdma_init_payload(const struct qib_devdata *dd,
                      struct qib_user_sdma_queue *pq,
                      struct qib_user_sdma_pkt *pkt,
                      const struct iovec *iov,
                      unsigned long niov, int npages)
{
    int ret = 0;

    if (npages >= ARRAY_SIZE(pkt->addr))
        ret = qib_user_sdma_coalesce(dd, pkt, iov, niov);
    else
        ret = qib_user_sdma_pin_pkt(dd, pq, pkt, iov, niov);

    return ret;
}

/* free a packet list -- return counter value of last packet */
static void qib_user_sdma_free_pkt_list(struct device *dev,
                    struct qib_user_sdma_queue *pq,
                    struct list_head *list)
{
    struct qib_user_sdma_pkt *pkt, *pkt_next;

    list_for_each_entry_safe(pkt, pkt_next, list, list) {
        int i;

        for (i = 0; i < pkt->naddr; i++)
            qib_user_sdma_free_pkt_frag(dev, pq, pkt, i);

        kmem_cache_free(pq->pkt_slab, pkt);
    }
    INIT_LIST_HEAD(list);
}

/*
 * copy headers, coalesce etc -- pq->lock must be held
 *
 * we queue all the packets to list, returning the
 * number of bytes total.  list must be empty initially,
 * as, if there is an error we clean it...
 */
static int qib_user_sdma_queue_pkts(const struct qib_devdata *dd,
                    struct qib_user_sdma_queue *pq,
                    struct list_head *list,
                    const struct iovec *iov,
                    unsigned long niov,
                    int maxpkts)
{
    unsigned long idx = 0;
    int ret = 0;
    int npkts = 0;
    struct page *page = NULL;
    __le32 *pbc;
    dma_addr_t dma_addr;
    struct qib_user_sdma_pkt *pkt = NULL;
    size_t len;
    size_t nw;
    u32 counter = pq->counter;
    int dma_mapped = 0;

    while (idx < niov && npkts < maxpkts) {
        const unsigned long addr = (unsigned long) iov[idx].iov_base;
        const unsigned long idx_save = idx;
        unsigned pktnw;
        unsigned pktnwc;
        int nfrags = 0;
        int npages = 0;
        int cfur;

        dma_mapped = 0;
        len = iov[idx].iov_len;
        nw = len >> 2;
        page = NULL;

        pkt = kmem_cache_alloc(pq->pkt_slab, GFP_KERNEL);
        if (!pkt) {
            ret = -ENOMEM;
            goto free_list;
        }

        if (len < QIB_USER_SDMA_MIN_HEADER_LENGTH ||
            len > PAGE_SIZE || len & 3 || addr & 3) {
            ret = -EINVAL;
            goto free_pkt;
        }

        if (len == QIB_USER_SDMA_EXP_HEADER_LENGTH)
            pbc = dma_pool_alloc(pq->header_cache, GFP_KERNEL,
                         &dma_addr);
        else
            pbc = NULL;

        if (!pbc) {
            page = alloc_page(GFP_KERNEL);
            if (!page) {
                ret = -ENOMEM;
                goto free_pkt;
            }
            pbc = kmap(page);
        }

        cfur = copy_from_user(pbc, iov[idx].iov_base, len);
        if (cfur) {
            ret = -EFAULT;
            goto free_pbc;
        }

        /*
         * This assignment is a bit strange.  it's because the
         * the pbc counts the number of 32 bit words in the full
         * packet _except_ the first word of the pbc itself...
         */
        pktnwc = nw - 1;

        /*
         * pktnw computation yields the number of 32 bit words
         * that the caller has indicated in the PBC.  note that
         * this is one less than the total number of words that
         * goes to the send DMA engine as the first 32 bit word
         * of the PBC itself is not counted.  Armed with this count,
         * we can verify that the packet is consistent with the
         * iovec lengths.
         */
        pktnw = le32_to_cpu(*pbc) & QIB_PBC_LENGTH_MASK;
        if (pktnw < pktnwc || pktnw > pktnwc + (PAGE_SIZE >> 2)) {
            ret = -EINVAL;
            goto free_pbc;
        }

        idx++;
        while (pktnwc < pktnw && idx < niov) {
            const size_t slen = iov[idx].iov_len;
            const unsigned long faddr =
                (unsigned long) iov[idx].iov_base;

            if (slen & 3 || faddr & 3 || !slen ||
                slen > PAGE_SIZE) {
                ret = -EINVAL;
                goto free_pbc;
            }

            npages++;
            if ((faddr & PAGE_MASK) !=
                ((faddr + slen - 1) & PAGE_MASK))
                npages++;

            pktnwc += slen >> 2;
            idx++;
            nfrags++;
        }

        if (pktnwc != pktnw) {
            ret = -EINVAL;
            goto free_pbc;
        }

        if (page) {
            dma_addr = dma_map_page(&dd->pcidev->dev,
                        page, 0, len, DMA_TO_DEVICE);
            if (dma_mapping_error(&dd->pcidev->dev, dma_addr)) {
                ret = -ENOMEM;
                goto free_pbc;
            }

            dma_mapped = 1;
        }

        qib_user_sdma_init_header(pkt, counter, 0, len, dma_mapped,
                      page, pbc, dma_addr);

        if (nfrags) {
            ret = qib_user_sdma_init_payload(dd, pq, pkt,
                             iov + idx_save + 1,
                             nfrags, npages);
            if (ret < 0)
                goto free_pbc_dma;
        }

        counter++;
        npkts++;

        list_add_tail(&pkt->list, list);
    }

    ret = idx;
    goto done;

free_pbc_dma:
    if (dma_mapped)
        dma_unmap_page(&dd->pcidev->dev, dma_addr, len, DMA_TO_DEVICE);
free_pbc:
    if (page) {
        kunmap(page);
        __free_page(page);
    } else
        dma_pool_free(pq->header_cache, pbc, dma_addr);
free_pkt:
    kmem_cache_free(pq->pkt_slab, pkt);
free_list:
    qib_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, list);
done:
    return ret;
}

static void qib_user_sdma_set_complete_counter(struct qib_user_sdma_queue *pq,
                           u32 c)
{
    pq->sent_counter = c;
}

/* try to clean out queue -- needs pq->lock */
static int qib_user_sdma_queue_clean(struct qib_pportdata *ppd,
                     struct qib_user_sdma_queue *pq)
{
    struct qib_devdata *dd = ppd->dd;
    struct list_head free_list;
    struct qib_user_sdma_pkt *pkt;
    struct qib_user_sdma_pkt *pkt_prev;
    int ret = 0;

    INIT_LIST_HEAD(&free_list);

    list_for_each_entry_safe(pkt, pkt_prev, &pq->sent, list) {
        s64 descd = ppd->sdma_descq_removed - pkt->added;

        if (descd < 0)
            break;

        list_move_tail(&pkt->list, &free_list);

        /* one more packet cleaned */
        ret++;
    }

    if (!list_empty(&free_list)) {
        u32 counter;

        pkt = list_entry(free_list.prev,
                 struct qib_user_sdma_pkt, list);
        counter = pkt->counter;

        qib_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, &free_list);
        qib_user_sdma_set_complete_counter(pq, counter);
    }

    return ret;
}

void qib_user_sdma_queue_destroy(struct qib_user_sdma_queue *pq)
{
    if (!pq)
        return;

    kmem_cache_destroy(pq->pkt_slab);
    dma_pool_destroy(pq->header_cache);
    kfree(pq);
}

/* clean descriptor queue, returns > 0 if some elements cleaned */
static int qib_user_sdma_hwqueue_clean(struct qib_pportdata *ppd)
{
    int ret;
    unsigned long flags;

    spin_lock_irqsave(&ppd->sdma_lock, flags);
    ret = qib_sdma_make_progress(ppd);
    spin_unlock_irqrestore(&ppd->sdma_lock, flags);

    return ret;
}

/* we're in close, drain packets so that we can cleanup successfully... */
void qib_user_sdma_queue_drain(struct qib_pportdata *ppd,
                   struct qib_user_sdma_queue *pq)
{
    struct qib_devdata *dd = ppd->dd;
    int i;

    if (!pq)
        return;

    for (i = 0; i < QIB_USER_SDMA_DRAIN_TIMEOUT; i++) {
        mutex_lock(&pq->lock);
        if (list_empty(&pq->sent)) {
            mutex_unlock(&pq->lock);
            break;
        }
        qib_user_sdma_hwqueue_clean(ppd);
        qib_user_sdma_queue_clean(ppd, pq);
        mutex_unlock(&pq->lock);
        msleep(10);
    }

    if (!list_empty(&pq->sent)) {
        struct list_head free_list;

        qib_dev_err(dd, "user sdma lists not empty: forcing!\n");
        INIT_LIST_HEAD(&free_list);
        mutex_lock(&pq->lock);
        list_splice_init(&pq->sent, &free_list);
        qib_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, &free_list);
        mutex_unlock(&pq->lock);
    }
}

static inline __le64 qib_sdma_make_desc0(struct qib_pportdata *ppd,
                     u64 addr, u64 dwlen, u64 dwoffset)
{
    u8 tmpgen;

    tmpgen = ppd->sdma_generation;

    return cpu_to_le64(/* SDmaPhyAddr[31:0] */
               ((addr & 0xfffffffcULL) << 32) |
               /* SDmaGeneration[1:0] */
               ((tmpgen & 3ULL) << 30) |
               /* SDmaDwordCount[10:0] */
               ((dwlen & 0x7ffULL) << 16) |
               /* SDmaBufOffset[12:2] */
               (dwoffset & 0x7ffULL));
}

static inline __le64 qib_sdma_make_first_desc0(__le64 descq)
{
    return descq | cpu_to_le64(1ULL << 12);
}

static inline __le64 qib_sdma_make_last_desc0(__le64 descq)
{
                          /* last */  /* dma head */
    return descq | cpu_to_le64(1ULL << 11 | 1ULL << 13);
}

static inline __le64 qib_sdma_make_desc1(u64 addr)
{
    /* SDmaPhyAddr[47:32] */
    return cpu_to_le64(addr >> 32);
}

static void qib_user_sdma_send_frag(struct qib_pportdata *ppd,
                    struct qib_user_sdma_pkt *pkt, int idx,
                    unsigned ofs, u16 tail)
{
    const u64 addr = (u64) pkt->addr[idx].addr +
        (u64) pkt->addr[idx].offset;
    const u64 dwlen = (u64) pkt->addr[idx].length / 4;
    __le64 *descqp;
    __le64 descq0;

    descqp = &ppd->sdma_descq[tail].qw[0];

    descq0 = qib_sdma_make_desc0(ppd, addr, dwlen, ofs);
    if (idx == 0)
        descq0 = qib_sdma_make_first_desc0(descq0);
    if (idx == pkt->naddr - 1)
        descq0 = qib_sdma_make_last_desc0(descq0);

    descqp[0] = descq0;
    descqp[1] = qib_sdma_make_desc1(addr);
}

/* pq->lock must be held, get packets on the wire... */
static int qib_user_sdma_push_pkts(struct qib_pportdata *ppd,
                   struct qib_user_sdma_queue *pq,
                   struct list_head *pktlist)
{
    struct qib_devdata *dd = ppd->dd;
    int ret = 0;
    unsigned long flags;
    u16 tail;
    u8 generation;
    u64 descq_added;

    if (list_empty(pktlist))
        return 0;

    if (unlikely(!(ppd->lflags & QIBL_LINKACTIVE)))
        return -ECOMM;

    spin_lock_irqsave(&ppd->sdma_lock, flags);

    /* keep a copy for restoring purposes in case of problems */
    generation = ppd->sdma_generation;
    descq_added = ppd->sdma_descq_added;

    if (unlikely(!__qib_sdma_running(ppd))) {
        ret = -ECOMM;
        goto unlock;
    }

    tail = ppd->sdma_descq_tail;
    while (!list_empty(pktlist)) {
        struct qib_user_sdma_pkt *pkt =
            list_entry(pktlist->next, struct qib_user_sdma_pkt,
                   list);
        int i;
        unsigned ofs = 0;
        u16 dtail = tail;

        if (pkt->naddr > qib_sdma_descq_freecnt(ppd))
            goto unlock_check_tail;

        for (i = 0; i < pkt->naddr; i++) {
            qib_user_sdma_send_frag(ppd, pkt, i, ofs, tail);
            ofs += pkt->addr[i].length >> 2;

            if (++tail == ppd->sdma_descq_cnt) {
                tail = 0;
                ++ppd->sdma_generation;
            }
        }

        if ((ofs << 2) > ppd->ibmaxlen) {
            ret = -EMSGSIZE;
            goto unlock;
        }

        /*
         * If the packet is >= 2KB mtu equivalent, we have to use
         * the large buffers, and have to mark each descriptor as
         * part of a large buffer packet.
         */
        if (ofs > dd->piosize2kmax_dwords) {
            for (i = 0; i < pkt->naddr; i++) {
                ppd->sdma_descq[dtail].qw[0] |=
                    cpu_to_le64(1ULL << 14);
                if (++dtail == ppd->sdma_descq_cnt)
                    dtail = 0;
            }
        }

        ppd->sdma_descq_added += pkt->naddr;
        pkt->added = ppd->sdma_descq_added;
        list_move_tail(&pkt->list, &pq->sent);
        ret++;
    }

unlock_check_tail:
    /* advance the tail on the chip if necessary */
    if (ppd->sdma_descq_tail != tail)
        dd->f_sdma_update_tail(ppd, tail);

unlock:
    if (unlikely(ret < 0)) {
        ppd->sdma_generation = generation;
        ppd->sdma_descq_added = descq_added;
    }
    spin_unlock_irqrestore(&ppd->sdma_lock, flags);

    return ret;
}

int qib_user_sdma_writev(struct qib_ctxtdata *rcd,
             struct qib_user_sdma_queue *pq,
             const struct iovec *iov,
             unsigned long dim)
{
    struct qib_devdata *dd = rcd->dd;
    struct qib_pportdata *ppd = rcd->ppd;
    int ret = 0;
    struct list_head list;
    int npkts = 0;

    INIT_LIST_HEAD(&list);

    mutex_lock(&pq->lock);

    /* why not -ECOMM like qib_user_sdma_push_pkts() below? */
    if (!qib_sdma_running(ppd))
        goto done_unlock;

    if (ppd->sdma_descq_added != ppd->sdma_descq_removed) {
        qib_user_sdma_hwqueue_clean(ppd);
        qib_user_sdma_queue_clean(ppd, pq);
    }

    while (dim) {
        const int mxp = 8;

        down_write(&current->mm->mmap_sem);
        ret = qib_user_sdma_queue_pkts(dd, pq, &list, iov, dim, mxp);
        up_write(&current->mm->mmap_sem);

        if (ret <= 0)
            goto done_unlock;
        else {
            dim -= ret;
            iov += ret;
        }

        /* force packets onto the sdma hw queue... */
        if (!list_empty(&list)) {
            /*
             * Lazily clean hw queue.  the 4 is a guess of about
             * how many sdma descriptors a packet will take (it
             * doesn't have to be perfect).
             */
            if (qib_sdma_descq_freecnt(ppd) < ret * 4) {
                qib_user_sdma_hwqueue_clean(ppd);
                qib_user_sdma_queue_clean(ppd, pq);
            }

            ret = qib_user_sdma_push_pkts(ppd, pq, &list);
            if (ret < 0)
                goto done_unlock;
            else {
                npkts += ret;
                pq->counter += ret;

                if (!list_empty(&list))
                    goto done_unlock;
            }
        }
    }

done_unlock:
    if (!list_empty(&list))
        qib_user_sdma_free_pkt_list(&dd->pcidev->dev, pq, &list);
    mutex_unlock(&pq->lock);

    return (ret < 0) ? ret : npkts;
}

int qib_user_sdma_make_progress(struct qib_pportdata *ppd,
                struct qib_user_sdma_queue *pq)
{
    int ret = 0;

    mutex_lock(&pq->lock);
    qib_user_sdma_hwqueue_clean(ppd);
    ret = qib_user_sdma_queue_clean(ppd, pq);
    mutex_unlock(&pq->lock);

    return ret;
}

u32 qib_user_sdma_complete_counter(const struct qib_user_sdma_queue *pq)
{
    return pq ? pq->sent_counter : 0;
}

u32 qib_user_sdma_inflight_counter(struct qib_user_sdma_queue *pq)
{
    return pq ? pq->counter : 0;
}