lan743x: Fix TX Stall Issue

It has been observed that tx queue stalls while downloading
from certain web sites (example www.speedtest.net)

The cause has been tracked down to a corner case where
dma descriptors where not setup properly. And there for a tx
completion interrupt was not signaled.

This fix corrects the problem by properly marking the end of
a multi descriptor transmission.

Fixes: 23f0703c125b ("lan743x: Add main source files for new lan743x driver")
Signed-off-by: Bryan Whitehead <Bryan.Whitehead@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 4 deletions

diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
index 310807ef328b..4d1b4a24907f 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -1400,7 +1400,8 @@ static int lan743x_tx_frame_start(struct lan743x_tx *tx,
 }
 
 static void lan743x_tx_frame_add_lso(struct lan743x_tx *tx,
-                                     unsigned int frame_length)
+                                     unsigned int frame_length,
+                                     int nr_frags)
 {
         /* called only from within lan743x_tx_xmit_frame.
          * assuming tx->ring_lock has already been acquired.
@@ -1410,6 +1411,10 @@ static void lan743x_tx_frame_add_lso(struct lan743x_tx *tx,
 
         /* wrap up previous descriptor */
         tx->frame_data0 |= TX_DESC_DATA0_EXT_;
+        if (nr_frags <= 0) {
+                tx->frame_data0 |= TX_DESC_DATA0_LS_;
+                tx->frame_data0 |= TX_DESC_DATA0_IOC_;
+        }
         tx_descriptor = &tx->ring_cpu_ptr[tx->frame_tail];
         tx_descriptor->data0 = tx->frame_data0;
 
@@ -1514,8 +1519,11 @@ static void lan743x_tx_frame_end(struct lan743x_tx *tx,
         u32 tx_tail_flags = 0;
 
         /* wrap up previous descriptor */
-        tx->frame_data0 |= TX_DESC_DATA0_LS_;
-        tx->frame_data0 |= TX_DESC_DATA0_IOC_;
+        if ((tx->frame_data0 & TX_DESC_DATA0_DTYPE_MASK_) ==
+            TX_DESC_DATA0_DTYPE_DATA_) {
+                tx->frame_data0 |= TX_DESC_DATA0_LS_;
+                tx->frame_data0 |= TX_DESC_DATA0_IOC_;
+        }
 
         tx_descriptor = &tx->ring_cpu_ptr[tx->frame_tail];
         buffer_info = &tx->buffer_info[tx->frame_tail];
@@ -1600,7 +1608,7 @@ static netdev_tx_t lan743x_tx_xmit_frame(struct lan743x_tx *tx,
         }
 
         if (gso)
-                lan743x_tx_frame_add_lso(tx, frame_length);
+                lan743x_tx_frame_add_lso(tx, frame_length, nr_frags);
 
         if (nr_frags <= 0)
                 goto finish;