[PATCH v1 net] lan743x: Fix TX Stall Issue

[Bryan Whitehead]

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.whiteh...@microchip.com>
---
 drivers/net/ethernet/microchip/lan743x_main.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/microchip/lan743x_main.c 
b/drivers/net/ethernet/microchip/lan743x_main.c
index 310807e..4d1b4a2 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;
-- 
2.7.4