1 files changed, 105 insertions, 81 deletions

diff --git a/drivers/char/synclink_gt.c b/drivers/char/synclink_gt.c
index 8678f0c8699d..4561ce2fba6d 100644
--- a/drivers/char/synclink_gt.c
+++ b/drivers/char/synclink_gt.c
@@ -468,7 +468,7 @@ static unsigned int free_tbuf_count(struct slgt_info *info);
 static unsigned int tbuf_bytes(struct slgt_info *info);
 static void reset_tbufs(struct slgt_info *info);
 static void tdma_reset(struct slgt_info *info);
-static void tx_load(struct slgt_info *info, const char *buf, unsigned int count);
+static bool tx_load(struct slgt_info *info, const char *buf, unsigned int count);
 
 static void get_signals(struct slgt_info *info);
 static void set_signals(struct slgt_info *info);
@@ -813,59 +813,32 @@ static int write(struct tty_struct *tty,
         int ret = 0;
         struct slgt_info *info = tty->driver_data;
         unsigned long flags;
-        unsigned int bufs_needed;
 
         if (sanity_check(info, tty->name, "write"))
-                goto cleanup;
+                return -EIO;
+
         DBGINFO(("%s write count=%d\n", info->device_name, count));
 
-        if (!info->tx_buf)
-                goto cleanup;
+        if (!info->tx_buf || (count > info->max_frame_size))
+                return -EIO;
 
-        if (count > info->max_frame_size) {
-                ret = -EIO;
-                goto cleanup;
-        }
+        if (!count || tty->stopped || tty->hw_stopped)
+                return 0;
 
-        if (!count)
-                goto cleanup;
+        spin_lock_irqsave(&info->lock, flags);
 
-        if (!info->tx_active && info->tx_count) {
+        if (info->tx_count) {
                 /* send accumulated data from send_char() */
-                tx_load(info, info->tx_buf, info->tx_count);
-                goto start;
+                if (!tx_load(info, info->tx_buf, info->tx_count))
+                        goto cleanup;
+                info->tx_count = 0;
         }
-        bufs_needed = (count/DMABUFSIZE);
-        if (count % DMABUFSIZE)
-                ++bufs_needed;
-        if (bufs_needed > free_tbuf_count(info))
-                goto cleanup;
 
-        ret = info->tx_count = count;
-        tx_load(info, buf, count);
-        goto start;
-
-start:
-        if (info->tx_count && !tty->stopped && !tty->hw_stopped) {
-                spin_lock_irqsave(&info->lock,flags);
-                if (!info->tx_active)
-                        tx_start(info);
-                else if (!(rd_reg32(info, TDCSR) & BIT0)) {
-                        /* transmit still active but transmit DMA stopped */
-                        unsigned int i = info->tbuf_current;
-                        if (!i)
-                                i = info->tbuf_count;
-                        i--;
-                        /* if DMA buf unsent must try later after tx idle */
-                        if (desc_count(info->tbufs[i]))
-                                ret = 0;
-                }
-                if (ret > 0)
-                        update_tx_timer(info);
-                spin_unlock_irqrestore(&info->lock,flags);
-        }
+        if (tx_load(info, buf, count))
+                ret = count;
 
 cleanup:
+        spin_unlock_irqrestore(&info->lock, flags);
         DBGINFO(("%s write rc=%d\n", info->device_name, ret));
         return ret;
 }
@@ -882,7 +855,7 @@ static int put_char(struct tty_struct *tty, unsigned char ch)
         if (!info->tx_buf)
                 return 0;
         spin_lock_irqsave(&info->lock,flags);
-        if (!info->tx_active && (info->tx_count < info->max_frame_size)) {
+        if (info->tx_count < info->max_frame_size) {
                 info->tx_buf[info->tx_count++] = ch;
                 ret = 1;
         }
@@ -981,10 +954,8 @@ static void flush_chars(struct tty_struct *tty)
         DBGINFO(("%s flush_chars start transmit\n", info->device_name));
 
         spin_lock_irqsave(&info->lock,flags);
-        if (!info->tx_active && info->tx_count) {
-                tx_load(info, info->tx_buf,info->tx_count);
-                tx_start(info);
-        }
+        if (info->tx_count && tx_load(info, info->tx_buf, info->tx_count))
+                info->tx_count = 0;
         spin_unlock_irqrestore(&info->lock,flags);
 }
 
@@ -997,10 +968,9 @@ static void flush_buffer(struct tty_struct *tty)
                 return;
         DBGINFO(("%s flush_buffer\n", info->device_name));
 
-        spin_lock_irqsave(&info->lock,flags);
-        if (!info->tx_active)
-                info->tx_count = 0;
-        spin_unlock_irqrestore(&info->lock,flags);
+        spin_lock_irqsave(&info->lock, flags);
+        info->tx_count = 0;
+        spin_unlock_irqrestore(&info->lock, flags);
 
         tty_wakeup(tty);
 }
@@ -1033,12 +1003,10 @@ static void tx_release(struct tty_struct *tty)
         if (sanity_check(info, tty->name, "tx_release"))
                 return;
         DBGINFO(("%s tx_release\n", info->device_name));
-        spin_lock_irqsave(&info->lock,flags);
-        if (!info->tx_active && info->tx_count) {
-                tx_load(info, info->tx_buf, info->tx_count);
-                tx_start(info);
-        }
-        spin_unlock_irqrestore(&info->lock,flags);
+        spin_lock_irqsave(&info->lock, flags);
+        if (info->tx_count && tx_load(info, info->tx_buf, info->tx_count))
+                info->tx_count = 0;
+        spin_unlock_irqrestore(&info->lock, flags);
 }
 
 /*
@@ -1506,27 +1474,25 @@ static netdev_tx_t hdlcdev_xmit(struct sk_buff *skb,
 
         DBGINFO(("%s hdlc_xmit\n", dev->name));
 
+        if (!skb->len)
+                return NETDEV_TX_OK;
+
         /* stop sending until this frame completes */
         netif_stop_queue(dev);
 
-        /* copy data to device buffers */
-        info->tx_count = skb->len;
-        tx_load(info, skb->data, skb->len);
-
         /* update network statistics */
         dev->stats.tx_packets++;
         dev->stats.tx_bytes += skb->len;
 
-        /* done with socket buffer, so free it */
-        dev_kfree_skb(skb);
-
         /* save start time for transmit timeout detection */
         dev->trans_start = jiffies;
 
-        spin_lock_irqsave(&info->lock,flags);
-        tx_start(info);
-        update_tx_timer(info);
-        spin_unlock_irqrestore(&info->lock,flags);
+        spin_lock_irqsave(&info->lock, flags);
+        tx_load(info, skb->data, skb->len);
+        spin_unlock_irqrestore(&info->lock, flags);
+
+        /* done with socket buffer, so free it */
+        dev_kfree_skb(skb);
 
         return NETDEV_TX_OK;
 }
@@ -2180,7 +2146,7 @@ static void isr_serial(struct slgt_info *info)
 
         if (info->params.mode == MGSL_MODE_ASYNC) {
                 if (status & IRQ_TXIDLE) {
-                        if (info->tx_count)
+                        if (info->tx_active)
                                 isr_txeom(info, status);
                 }
                 if (info->rx_pio && (status & IRQ_RXDATA))
@@ -2276,13 +2242,42 @@ static void isr_tdma(struct slgt_info *info)
         }
 }
 
+/*
+ * return true if there are unsent tx DMA buffers, otherwise false
+ *
+ * if there are unsent buffers then info->tbuf_start
+ * is set to index of first unsent buffer
+ */
+static bool unsent_tbufs(struct slgt_info *info)
+{
+        unsigned int i = info->tbuf_current;
+        bool rc = false;
+
+        /*
+         * search backwards from last loaded buffer (precedes tbuf_current)
+         * for first unsent buffer (desc_count > 0)
+         */
+
+        do {
+                if (i)
+                        i--;
+                else
+                        i = info->tbuf_count - 1;
+                if (!desc_count(info->tbufs[i]))
+                        break;
+                info->tbuf_start = i;
+                rc = true;
+        } while (i != info->tbuf_current);
+
+        return rc;
+}
+
 static void isr_txeom(struct slgt_info *info, unsigned short status)
 {
         DBGISR(("%s txeom status=%04x\n", info->device_name, status));
 
         slgt_irq_off(info, IRQ_TXDATA + IRQ_TXIDLE + IRQ_TXUNDER);
         tdma_reset(info);
-        reset_tbufs(info);
         if (status & IRQ_TXUNDER) {
                 unsigned short val = rd_reg16(info, TCR);
                 wr_reg16(info, TCR, (unsigned short)(val | BIT2)); /* set reset bit */
@@ -2297,8 +2292,12 @@ static void isr_txeom(struct slgt_info *info, unsigned short status)
                                 info->icount.txok++;
                 }
 
+                if (unsent_tbufs(info)) {
+                        tx_start(info);
+                        update_tx_timer(info);
+                        return;
+                }
                 info->tx_active = false;
-                info->tx_count = 0;
 
                 del_timer(&info->tx_timer);
 
@@ -3949,7 +3948,7 @@ static void tx_start(struct slgt_info *info)
                 info->tx_enabled = true;
         }
 
-        if (info->tx_count) {
+        if (desc_count(info->tbufs[info->tbuf_start])) {
                 info->drop_rts_on_tx_done = false;
 
                 if (info->params.mode != MGSL_MODE_ASYNC) {
@@ -4772,25 +4771,36 @@ static unsigned int tbuf_bytes(struct slgt_info *info)
 }
 
 /*
- * load transmit DMA buffer(s) with data
+ * load data into transmit DMA buffer ring and start transmitter if needed
+ * return true if data accepted, otherwise false (buffers full)
  */
-static void tx_load(struct slgt_info *info, const char *buf, unsigned int size)
+static bool tx_load(struct slgt_info *info, const char *buf, unsigned int size)
 {
         unsigned short count;
         unsigned int i;
         struct slgt_desc *d;
 
-        if (size == 0)
-                return;
+        /* check required buffer space */
+        if (DIV_ROUND_UP(size, DMABUFSIZE) > free_tbuf_count(info))
+                return false;
 
         DBGDATA(info, buf, size, "tx");
 
+        /*
+         * copy data to one or more DMA buffers in circular ring
+         * tbuf_start   = first buffer for this data
+         * tbuf_current = next free buffer
+         *
+         * Copy all data before making data visible to DMA controller by
+         * setting descriptor count of the first buffer.
+         * This prevents an active DMA controller from reading the first DMA
+         * buffers of a frame and stopping before the final buffers are filled.
+         */
+
         info->tbuf_start = i = info->tbuf_current;
 
         while (size) {
                 d = &info->tbufs[i];
-                if (++i == info->tbuf_count)
-                        i = 0;
 
                 count = (unsigned short)((size > DMABUFSIZE) ? DMABUFSIZE : size);
                 memcpy(d->buf, buf, count);
@@ -4808,11 +4818,27 @@ static void tx_load(struct slgt_info *info, const char *buf, unsigned int size)
                 else
                         set_desc_eof(*d, 0);
 
-                set_desc_count(*d, count);
+                /* set descriptor count for all but first buffer */
+                if (i != info->tbuf_start)
+                        set_desc_count(*d, count);
                 d->buf_count = count;
+
+                if (++i == info->tbuf_count)
+                        i = 0;
         }
 
         info->tbuf_current = i;
+
+        /* set first buffer count to make new data visible to DMA controller */
+        d = &info->tbufs[info->tbuf_start];
+        set_desc_count(*d, d->buf_count);
+
+        /* start transmitter if needed and update transmit timeout */
+        if (!info->tx_active)
+                tx_start(info);
+        update_tx_timer(info);
+
+        return true;
 }
 
 static int register_test(struct slgt_info *info)
@@ -4934,9 +4960,7 @@ static int loopback_test(struct slgt_info *info)
         spin_lock_irqsave(&info->lock,flags);
         async_mode(info);
         rx_start(info);
-        info->tx_count = count;
         tx_load(info, buf, count);
-        tx_start(info);
         spin_unlock_irqrestore(&info->lock, flags);
 
         /* wait for receive complete */