[PATCH 4.20 34/76] lan743x: Fix TX Stall Issue

Greg Kroah-Hartman
2019-03-08T12:56:56Z

From: Bryan Whitehead <Bryan.Whitehead@microchip.com>

[ Upstream commit 90490ef7269906423a1c1b917fc24be8b1602658 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/microchip/lan743x_main.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

--- 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
}

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(str

/* 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
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
}

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;