layer2.c

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/*
 * PCBIT-D low-layer interface
 *
 * Copyright (C) 1996 Universidade de Lisboa
 *
 * Written by Pedro Roque Marques ([email protected])
 *
 * This software may be used and distributed according to the terms of
 * the GNU General Public License, incorporated herein by reference.
 */

/*
 * 19991203 - Fernando Carvalho - [email protected]
 * Hacked to compile with egcs and run with current version of isdn modules
 */

/*
 *        Based on documentation provided by Inesc:
 *        - "Interface com bus do PC para o PCBIT e PCBIT-D", Inesc, Jan 93
 */

/*
 *        TODO: better handling of errors
 *              re-write/remove debug printks
 */

#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/workqueue.h>
#include <linux/mm.h>
#include <linux/skbuff.h>

#include <linux/isdnif.h>

#include <asm/io.h>


#include "pcbit.h"
#include "layer2.h"
#include "edss1.h"

#undef DEBUG_FRAG


/*
 *  Prototypes
 */

static void pcbit_transmit(struct pcbit_dev *dev);

static void pcbit_recv_ack(struct pcbit_dev *dev, unsigned char ack);

static void pcbit_l2_error(struct pcbit_dev *dev);
static void pcbit_l2_active_conf(struct pcbit_dev *dev, u_char info);
static void pcbit_l2_err_recover(unsigned long data);

static void pcbit_firmware_bug(struct pcbit_dev *dev);

static __inline__ void
pcbit_sched_delivery(struct pcbit_dev *dev)
{
    schedule_work(&dev->qdelivery);
}


/*
 *  Called from layer3
 */

int
pcbit_l2_write(struct pcbit_dev *dev, ulong msg, ushort refnum,
           struct sk_buff *skb, unsigned short hdr_len)
{
    struct frame_buf *frame,
        *ptr;
    unsigned long flags;

    if (dev->l2_state != L2_RUNNING && dev->l2_state != L2_LOADING) {
        dev_kfree_skb(skb);
        return -1;
    }
    if ((frame = kmalloc(sizeof(struct frame_buf),
                 GFP_ATOMIC)) == NULL) {
        printk(KERN_WARNING "pcbit_2_write: kmalloc failed\n");
        dev_kfree_skb(skb);
        return -1;
    }
    frame->msg = msg;
    frame->refnum = refnum;
    frame->copied = 0;
    frame->hdr_len = hdr_len;

    if (skb)
        frame->dt_len = skb->len - hdr_len;
    else
        frame->dt_len = 0;

    frame->skb = skb;

    frame->next = NULL;

    spin_lock_irqsave(&dev->lock, flags);

    if (dev->write_queue == NULL) {
        dev->write_queue = frame;
        spin_unlock_irqrestore(&dev->lock, flags);
        pcbit_transmit(dev);
    } else {
        for (ptr = dev->write_queue; ptr->next; ptr = ptr->next);
        ptr->next = frame;

        spin_unlock_irqrestore(&dev->lock, flags);
    }
    return 0;
}

static __inline__ void
pcbit_tx_update(struct pcbit_dev *dev, ushort len)
{
    u_char info;

    dev->send_seq = (dev->send_seq + 1) % 8;

    dev->fsize[dev->send_seq] = len;
    info = 0;
    info |= dev->rcv_seq << 3;
    info |= dev->send_seq;

    writeb(info, dev->sh_mem + BANK4);

}

/*
 * called by interrupt service routine or by write_2
 */

static void
pcbit_transmit(struct pcbit_dev *dev)
{
    struct frame_buf *frame = NULL;
    unsigned char unacked;
    int flen;               /* fragment frame length including all headers */
    int free;
    int count,
        cp_len;
    unsigned long flags;
    unsigned short tt;

    if (dev->l2_state != L2_RUNNING && dev->l2_state != L2_LOADING)
        return;

    unacked = (dev->send_seq + (8 - dev->unack_seq)) & 0x07;

    spin_lock_irqsave(&dev->lock, flags);

    if (dev->free > 16 && dev->write_queue && unacked < 7) {

        if (!dev->w_busy)
            dev->w_busy = 1;
        else {
            spin_unlock_irqrestore(&dev->lock, flags);
            return;
        }


        frame = dev->write_queue;
        free = dev->free;

        spin_unlock_irqrestore(&dev->lock, flags);

        if (frame->copied == 0) {

            /* Type 0 frame */

            ulong   msg;

            if (frame->skb)
                flen = FRAME_HDR_LEN + PREHDR_LEN + frame->skb->len;
            else
                flen = FRAME_HDR_LEN + PREHDR_LEN;

            if (flen > free)
                flen = free;

            msg = frame->msg;

            /*
             *  Board level 2 header
             */

            pcbit_writew(dev, flen - FRAME_HDR_LEN);

            pcbit_writeb(dev, GET_MSG_CPU(msg));

            pcbit_writeb(dev, GET_MSG_PROC(msg));

            /* TH */
            pcbit_writew(dev, frame->hdr_len + PREHDR_LEN);

            /* TD */
            pcbit_writew(dev, frame->dt_len);


            /*
             *  Board level 3 fixed-header
             */

            /* LEN = TH */
            pcbit_writew(dev, frame->hdr_len + PREHDR_LEN);

            /* XX */
            pcbit_writew(dev, 0);

            /* C + S */
            pcbit_writeb(dev, GET_MSG_CMD(msg));
            pcbit_writeb(dev, GET_MSG_SCMD(msg));

            /* NUM */
            pcbit_writew(dev, frame->refnum);

            count = FRAME_HDR_LEN + PREHDR_LEN;
        } else {
            /* Type 1 frame */

            flen = 2 + (frame->skb->len - frame->copied);

            if (flen > free)
                flen = free;

            /* TT */
            tt = ((ushort) (flen - 2)) | 0x8000U;   /* Type 1 */
            pcbit_writew(dev, tt);

            count = 2;
        }

        if (frame->skb) {
            cp_len = frame->skb->len - frame->copied;
            if (cp_len > flen - count)
                cp_len = flen - count;

            memcpy_topcbit(dev, frame->skb->data + frame->copied,
                       cp_len);
            frame->copied += cp_len;
        }
        /* bookkeeping */
        dev->free -= flen;
        pcbit_tx_update(dev, flen);

        spin_lock_irqsave(&dev->lock, flags);

        if (frame->skb == NULL || frame->copied == frame->skb->len) {

            dev->write_queue = frame->next;

            if (frame->skb != NULL) {
                /* free frame */
                dev_kfree_skb(frame->skb);
            }
            kfree(frame);
        }
        dev->w_busy = 0;
        spin_unlock_irqrestore(&dev->lock, flags);
    } else {
        spin_unlock_irqrestore(&dev->lock, flags);
#ifdef DEBUG
        printk(KERN_DEBUG "unacked %d free %d write_queue %s\n",
               unacked, dev->free, dev->write_queue ? "not empty" :
               "empty");
#endif
    }
}


/*
 *  deliver a queued frame to the upper layer
 */

void
pcbit_deliver(struct work_struct *work)
{
    struct frame_buf *frame;
    unsigned long flags, msg;
    struct pcbit_dev *dev =
        container_of(work, struct pcbit_dev, qdelivery);

    spin_lock_irqsave(&dev->lock, flags);

    while ((frame = dev->read_queue)) {
        dev->read_queue = frame->next;
        spin_unlock_irqrestore(&dev->lock, flags);

        msg = 0;
        SET_MSG_CPU(msg, 0);
        SET_MSG_PROC(msg, 0);
        SET_MSG_CMD(msg, frame->skb->data[2]);
        SET_MSG_SCMD(msg, frame->skb->data[3]);

        frame->refnum = *((ushort *)frame->skb->data + 4);
        frame->msg = *((ulong *)&msg);

        skb_pull(frame->skb, 6);

        pcbit_l3_receive(dev, frame->msg, frame->skb, frame->hdr_len,
                 frame->refnum);

        kfree(frame);

        spin_lock_irqsave(&dev->lock, flags);
    }

    spin_unlock_irqrestore(&dev->lock, flags);
}

/*
 * Reads BANK 2 & Reassembles
 */

static void
pcbit_receive(struct pcbit_dev *dev)
{
    unsigned short tt;
    u_char cpu,
        proc;
    struct frame_buf *frame = NULL;
    unsigned long flags;
    u_char type1;

    if (dev->l2_state != L2_RUNNING && dev->l2_state != L2_LOADING)
        return;

    tt = pcbit_readw(dev);

    if ((tt & 0x7fffU) > 511) {
        printk(KERN_INFO "pcbit: invalid frame length -> TT=%04x\n",
               tt);
        pcbit_l2_error(dev);
        return;
    }
    if (!(tt & 0x8000U)) {  /* Type 0 */
        type1 = 0;

        if (dev->read_frame) {
            printk(KERN_DEBUG "pcbit_receive: Type 0 frame and read_frame != NULL\n");
            /* discard previous queued frame */
            kfree_skb(dev->read_frame->skb);
            kfree(dev->read_frame);
            dev->read_frame = NULL;
        }
        frame = kzalloc(sizeof(struct frame_buf), GFP_ATOMIC);

        if (frame == NULL) {
            printk(KERN_WARNING "kmalloc failed\n");
            return;
        }

        cpu = pcbit_readb(dev);
        proc = pcbit_readb(dev);


        if (cpu != 0x06 && cpu != 0x02) {
            printk(KERN_DEBUG "pcbit: invalid cpu value\n");
            kfree(frame);
            pcbit_l2_error(dev);
            return;
        }
        /*
         * we discard cpu & proc on receiving
         * but we read it to update the pointer
         */

        frame->hdr_len = pcbit_readw(dev);
        frame->dt_len = pcbit_readw(dev);

        /*
         * 0 sized packet
         * I don't know if they are an error or not...
         * But they are very frequent
         * Not documented
         */

        if (frame->hdr_len == 0) {
            kfree(frame);
#ifdef DEBUG
            printk(KERN_DEBUG "0 sized frame\n");
#endif
            pcbit_firmware_bug(dev);
            return;
        }
        /* sanity check the length values */
        if (frame->hdr_len > 1024 || frame->dt_len > 2048) {
#ifdef DEBUG
            printk(KERN_DEBUG "length problem: ");
            printk(KERN_DEBUG "TH=%04x TD=%04x\n",
                   frame->hdr_len,
                   frame->dt_len);
#endif
            pcbit_l2_error(dev);
            kfree(frame);
            return;
        }
        /* minimum frame read */

        frame->skb = dev_alloc_skb(frame->hdr_len + frame->dt_len +
                       ((frame->hdr_len + 15) & ~15));

        if (!frame->skb) {
            printk(KERN_DEBUG "pcbit_receive: out of memory\n");
            kfree(frame);
            return;
        }
        /* 16 byte alignment for IP */
        if (frame->dt_len)
            skb_reserve(frame->skb, (frame->hdr_len + 15) & ~15);

    } else {
        /* Type 1 */
        type1 = 1;
        tt &= 0x7fffU;

        if (!(frame = dev->read_frame)) {
            printk("Type 1 frame and no frame queued\n");
            /* usually after an error: toss frame */
            dev->readptr += tt;
            if (dev->readptr > dev->sh_mem + BANK2 + BANKLEN)
                dev->readptr -= BANKLEN;
            return;

        }
    }

    memcpy_frompcbit(dev, skb_put(frame->skb, tt), tt);

    frame->copied += tt;
    spin_lock_irqsave(&dev->lock, flags);
    if (frame->copied == frame->hdr_len + frame->dt_len) {

        if (type1) {
            dev->read_frame = NULL;
        }
        if (dev->read_queue) {
            struct frame_buf *ptr;
            for (ptr = dev->read_queue; ptr->next; ptr = ptr->next);
            ptr->next = frame;
        } else
            dev->read_queue = frame;

    } else {
        dev->read_frame = frame;
    }
    spin_unlock_irqrestore(&dev->lock, flags);
}

/*
 *  The board sends 0 sized frames
 *  They are TDATA_CONFs that get messed up somehow
 *  gotta send a fake acknowledgment to the upper layer somehow
 */

static __inline__ void
pcbit_fake_conf(struct pcbit_dev *dev, struct pcbit_chan *chan)
{
    isdn_ctrl ictl;

    if (chan->queued) {
        chan->queued--;

        ictl.driver = dev->id;
        ictl.command = ISDN_STAT_BSENT;
        ictl.arg = chan->id;
        dev->dev_if->statcallb(&ictl);
    }
}

static void
pcbit_firmware_bug(struct pcbit_dev *dev)
{
    struct pcbit_chan *chan;

    chan = dev->b1;

    if (chan->fsm_state == ST_ACTIVE) {
        pcbit_fake_conf(dev, chan);
    }
    chan = dev->b2;

    if (chan->fsm_state == ST_ACTIVE) {
        pcbit_fake_conf(dev, chan);
    }
}

irqreturn_t
pcbit_irq_handler(int interrupt, void *devptr)
{
    struct pcbit_dev *dev;
    u_char info,
        ack_seq,
        read_seq;

    dev = (struct pcbit_dev *) devptr;

    if (!dev) {
        printk(KERN_WARNING "pcbit_irq_handler: wrong device\n");
        return IRQ_NONE;
    }
    if (dev->interrupt) {
        printk(KERN_DEBUG "pcbit: reentering interrupt hander\n");
        return IRQ_HANDLED;
    }
    dev->interrupt = 1;

    info = readb(dev->sh_mem + BANK3);

    if (dev->l2_state == L2_STARTING || dev->l2_state == L2_ERROR) {
        pcbit_l2_active_conf(dev, info);
        dev->interrupt = 0;
        return IRQ_HANDLED;
    }
    if (info & 0x40U) {     /* E bit set */
#ifdef DEBUG
        printk(KERN_DEBUG "pcbit_irq_handler: E bit on\n");
#endif
        pcbit_l2_error(dev);
        dev->interrupt = 0;
        return IRQ_HANDLED;
    }
    if (dev->l2_state != L2_RUNNING && dev->l2_state != L2_LOADING) {
        dev->interrupt = 0;
        return IRQ_HANDLED;
    }
    ack_seq = (info >> 3) & 0x07U;
    read_seq = (info & 0x07U);

    dev->interrupt = 0;

    if (read_seq != dev->rcv_seq) {
        while (read_seq != dev->rcv_seq) {
            pcbit_receive(dev);
            dev->rcv_seq = (dev->rcv_seq + 1) % 8;
        }
        pcbit_sched_delivery(dev);
    }
    if (ack_seq != dev->unack_seq) {
        pcbit_recv_ack(dev, ack_seq);
    }
    info = dev->rcv_seq << 3;
    info |= dev->send_seq;

    writeb(info, dev->sh_mem + BANK4);
    return IRQ_HANDLED;
}


static void
pcbit_l2_active_conf(struct pcbit_dev *dev, u_char info)
{
    u_char state;

    state = dev->l2_state;

#ifdef DEBUG
    printk(KERN_DEBUG "layer2_active_confirm\n");
#endif


    if (info & 0x80U) {
        dev->rcv_seq = info & 0x07U;
        dev->l2_state = L2_RUNNING;
    } else
        dev->l2_state = L2_DOWN;

    if (state == L2_STARTING)
        wake_up_interruptible(&dev->set_running_wq);

    if (state == L2_ERROR && dev->l2_state == L2_RUNNING) {
        pcbit_transmit(dev);
    }
}

static void
pcbit_l2_err_recover(unsigned long data)
{

    struct pcbit_dev *dev;
    struct frame_buf *frame;

    dev = (struct pcbit_dev *) data;

    del_timer(&dev->error_recover_timer);
    if (dev->w_busy || dev->r_busy) {
        init_timer(&dev->error_recover_timer);
        dev->error_recover_timer.expires = jiffies + ERRTIME;
        add_timer(&dev->error_recover_timer);
        return;
    }
    dev->w_busy = dev->r_busy = 1;

    if (dev->read_frame) {
        kfree_skb(dev->read_frame->skb);
        kfree(dev->read_frame);
        dev->read_frame = NULL;
    }
    if (dev->write_queue) {
        frame = dev->write_queue;
#ifdef FREE_ON_ERROR
        dev->write_queue = dev->write_queue->next;

        if (frame->skb) {
            dev_kfree_skb(frame->skb);
        }
        kfree(frame);
#else
        frame->copied = 0;
#endif
    }
    dev->rcv_seq = dev->send_seq = dev->unack_seq = 0;
    dev->free = 511;
    dev->l2_state = L2_ERROR;

    /* this is an hack... */
    pcbit_firmware_bug(dev);

    dev->writeptr = dev->sh_mem;
    dev->readptr = dev->sh_mem + BANK2;

    writeb((0x80U | ((dev->rcv_seq & 0x07) << 3) | (dev->send_seq & 0x07)),
           dev->sh_mem + BANK4);
    dev->w_busy = dev->r_busy = 0;

}

static void
pcbit_l2_error(struct pcbit_dev *dev)
{
    if (dev->l2_state == L2_RUNNING) {

        printk(KERN_INFO "pcbit: layer 2 error\n");

#ifdef DEBUG
        log_state(dev);
#endif

        dev->l2_state = L2_DOWN;

        init_timer(&dev->error_recover_timer);
        dev->error_recover_timer.function = &pcbit_l2_err_recover;
        dev->error_recover_timer.data = (ulong) dev;
        dev->error_recover_timer.expires = jiffies + ERRTIME;
        add_timer(&dev->error_recover_timer);
    }
}

/*
 * Description:
 * if board acks frames
 *   update dev->free
 *   call pcbit_transmit to write possible queued frames
 */

static void
pcbit_recv_ack(struct pcbit_dev *dev, unsigned char ack)
{
    int i,
        count;
    int unacked;

    unacked = (dev->send_seq + (8 - dev->unack_seq)) & 0x07;

    /* dev->unack_seq < ack <= dev->send_seq; */

    if (unacked) {

        if (dev->send_seq > dev->unack_seq) {
            if (ack <= dev->unack_seq || ack > dev->send_seq) {
                printk(KERN_DEBUG
                       "layer 2 ack unacceptable - dev %d",
                       dev->id);

                pcbit_l2_error(dev);
            } else if (ack > dev->send_seq && ack <= dev->unack_seq) {
                printk(KERN_DEBUG
                       "layer 2 ack unacceptable - dev %d",
                       dev->id);
                pcbit_l2_error(dev);
            }
        }
        /* ack is acceptable */


        i = dev->unack_seq;

        do {
            dev->unack_seq = i = (i + 1) % 8;
            dev->free += dev->fsize[i];
        } while (i != ack);

        count = 0;
        while (count < 7 && dev->write_queue) {
            u8 lsend_seq = dev->send_seq;

            pcbit_transmit(dev);

            if (dev->send_seq == lsend_seq)
                break;
            count++;
        }
    } else
        printk(KERN_DEBUG "recv_ack: unacked = 0\n");
}