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

/*
 * 19991203 - Fernando Carvalho - takion@superbofh.org
 * 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/system.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");
}