[PATCH net] stmmac: reset last TSO segment size after device open

[PATCH net] stmmac: reset last TSO segment size after device open

[Lars Persson]

The mss variable tracks the last max segment size sent to the TSO
engine. We do not update the hardware as long as we receive skb:s with
the same value in gso_size.

During a network device down/up cycle (mapped to stmmac_release() and
stmmac_open() callbacks) we issue a reset to the hardware and it
forgets the setting for mss. However we did not zero out our mss
variable so the next transmission of a gso packet happens with an
undefined hardware setting.

This triggers a hang in the TSO engine and eventuelly the netdev
watchdog will bark.

Fixes: f748be531d70 ("stmmac: support new GMAC4")
Signed-off-by: Lars Persson <larper@axis.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index f63c2ddced3c..d7250539d0bd 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -2588,6 +2588,7 @@ static int stmmac_open(struct net_device *dev)
 
 	priv->dma_buf_sz = STMMAC_ALIGN(buf_sz);
 	priv->rx_copybreak = STMMAC_RX_COPYBREAK;
+	priv->mss = 0;
 
 	ret = alloc_dma_desc_resources(priv);
 	if (ret < 0) {
-- 
2.11.0

Re: [PATCH net] stmmac: reset last TSO segment size after device open

[David Miller]

From: Lars Persson <lars.persson@axis.com>
Date: Fri,  1 Dec 2017 11:12:44 +0100

> The mss variable tracks the last max segment size sent to the TSO
> engine. We do not update the hardware as long as we receive skb:s with
> the same value in gso_size.
> 
> During a network device down/up cycle (mapped to stmmac_release() and
> stmmac_open() callbacks) we issue a reset to the hardware and it
> forgets the setting for mss. However we did not zero out our mss
> variable so the next transmission of a gso packet happens with an
> undefined hardware setting.
> 
> This triggers a hang in the TSO engine and eventuelly the netdev
> watchdog will bark.
> 
> Fixes: f748be531d70 ("stmmac: support new GMAC4")
> Signed-off-by: Lars Persson <larper@axis.com>

Applied and queued up for -stable, thanks.