1 files changed, 57 insertions, 2 deletions

diff --git a/drivers/char/synclink_gt.c b/drivers/char/synclink_gt.c
index 3cfc9e1f8882..8511e2e43c18 100644
--- a/drivers/char/synclink_gt.c
+++ b/drivers/char/synclink_gt.c
@@ -214,6 +214,7 @@ struct slgt_desc
         char *buf;          /* virtual  address of data buffer */
         unsigned int pdesc; /* physical address of this descriptor */
         dma_addr_t buf_dma_addr;
+        unsigned short buf_count;
 };
 
 #define set_desc_buffer(a,b) (a).pbuf = cpu_to_le32((unsigned int)(b))
@@ -466,6 +467,7 @@ static void tx_start(struct slgt_info *info);
 static void tx_stop(struct slgt_info *info);
 static void tx_set_idle(struct slgt_info *info);
 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 tdma_start(struct slgt_info *info);
@@ -1388,10 +1390,12 @@ done:
 static int chars_in_buffer(struct tty_struct *tty)
 {
         struct slgt_info *info = tty->driver_data;
+        int count;
         if (sanity_check(info, tty->name, "chars_in_buffer"))
                 return 0;
-        DBGINFO(("%s chars_in_buffer()=%d\n", info->device_name, info->tx_count));
-        return info->tx_count;
+        count = tbuf_bytes(info);
+        DBGINFO(("%s chars_in_buffer()=%d\n", info->device_name, count));
+        return count;
 }
 
 /*
@@ -4671,6 +4675,56 @@ static unsigned int free_tbuf_count(struct slgt_info *info)
 }
 
 /*
+ * return number of bytes in unsent transmit DMA buffers
+ * and the serial controller tx FIFO
+ */
+static unsigned int tbuf_bytes(struct slgt_info *info)
+{
+        unsigned int total_count = 0;
+        unsigned int i = info->tbuf_current;
+        unsigned int reg_value;
+        unsigned int count;
+        unsigned int active_buf_count = 0;
+
+        /*
+         * Add descriptor counts for all tx DMA buffers.
+         * If count is zero (cleared by DMA controller after read),
+         * the buffer is complete or is actively being read from.
+         *
+         * Record buf_count of last buffer with zero count starting
+         * from current ring position. buf_count is mirror
+         * copy of count and is not cleared by serial controller.
+         * If DMA controller is active, that buffer is actively
+         * being read so add to total.
+         */
+        do {
+                count = desc_count(info->tbufs[i]);
+                if (count)
+                        total_count += count;
+                else if (!total_count)
+                        active_buf_count = info->tbufs[i].buf_count;
+                if (++i == info->tbuf_count)
+                        i = 0;
+        } while (i != info->tbuf_current);
+
+        /* read tx DMA status register */
+        reg_value = rd_reg32(info, TDCSR);
+
+        /* if tx DMA active, last zero count buffer is in use */
+        if (reg_value & BIT0)
+                total_count += active_buf_count;
+
+        /* add tx FIFO count = reg_value[15..8] */
+        total_count += (reg_value >> 8) & 0xff;
+
+        /* if transmitter active add one byte for shift register */
+        if (info->tx_active)
+                total_count++;
+
+        return total_count;
+}
+
+/*
  * load transmit DMA buffer(s) with data
  */
 static void tx_load(struct slgt_info *info, const char *buf, unsigned int size)
@@ -4708,6 +4762,7 @@ static void tx_load(struct slgt_info *info, const char *buf, unsigned int size)
                         set_desc_eof(*d, 0);
 
                 set_desc_count(*d, count);
+                d->buf_count = count;
         }
 
         info->tbuf_current = i;