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From: Finn Thain <fthain@telegraphics.com.au>
To: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Chris Zankel <chris@zankel.net>,
	Laurent Vivier <laurent@vivier.eu>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	Stephen Hemminger <stephen@networkplumber.org>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH net v3 12/12] net/sonic: Prevent tx watchdog timeout
Date: Thu, 23 Jan 2020 09:07:26 +1100	[thread overview]
Message-ID: <0cdfbf008300aa5e18e34f9b199339f342a899a5.1579730846.git.fthain@telegraphics.com.au> (raw)
In-Reply-To: <cover.1579730846.git.fthain@telegraphics.com.au>

Section 5.5.3.2 of the datasheet says,

    If FIFO Underrun, Byte Count Mismatch, Excessive Collision, or
    Excessive Deferral (if enabled) errors occur, transmission ceases.

In this situation, the chip asserts a TXER interrupt rather than TXDN.
But the handler for the TXDN is the only way that the transmit queue
gets restarted. Hence, an aborted transmission can result in a watchdog
timeout.

This problem can be reproduced on congested link, as that can result in
excessive transmitter collisions. Another way to reproduce this is with
a FIFO Underrun, which may be caused by DMA latency.

In event of a TXER interrupt, prevent a watchdog timeout by restarting
transmission.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
---
 drivers/net/ethernet/natsemi/sonic.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/natsemi/sonic.c b/drivers/net/ethernet/natsemi/sonic.c
index 27b6f6585527..05e760444a92 100644
--- a/drivers/net/ethernet/natsemi/sonic.c
+++ b/drivers/net/ethernet/natsemi/sonic.c
@@ -415,10 +415,19 @@ static irqreturn_t sonic_interrupt(int irq, void *dev_id)
 			lp->stats.rx_missed_errors += 65536;
 
 		/* transmit error */
-		if (status & SONIC_INT_TXER)
-			if (SONIC_READ(SONIC_TCR) & SONIC_TCR_FU)
-				netif_dbg(lp, tx_err, dev, "%s: tx fifo underrun\n",
-					  __func__);
+		if (status & SONIC_INT_TXER) {
+			u16 tcr = SONIC_READ(SONIC_TCR);
+
+			netif_dbg(lp, tx_err, dev, "%s: TXER intr, TCR %04x\n",
+				  __func__, tcr);
+
+			if (tcr & (SONIC_TCR_EXD | SONIC_TCR_EXC |
+				   SONIC_TCR_FU | SONIC_TCR_BCM)) {
+				/* Aborted transmission. Try again. */
+				netif_stop_queue(dev);
+				SONIC_WRITE(SONIC_CMD, SONIC_CR_TXP);
+			}
+		}
 
 		/* bus retry */
 		if (status & SONIC_INT_BR) {
-- 
2.24.1


  parent reply	other threads:[~2020-01-22 22:24 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-22 22:07 [PATCH net v3 00/12] Fixes for SONIC ethernet driver Finn Thain
2020-01-22 22:07 ` [PATCH net v3 10/12] net/sonic: Fix command register usage Finn Thain
2020-01-22 22:07 ` [PATCH net v3 04/12] net/sonic: Fix interface error stats collection Finn Thain
2020-01-22 22:07 ` [PATCH net v3 08/12] net/sonic: Fix receive buffer replenishment Finn Thain
2020-01-22 22:07 ` [PATCH net v3 02/12] net/sonic: Clear interrupt flags immediately Finn Thain
2020-01-22 22:07 ` [PATCH net v3 06/12] net/sonic: Avoid needless receive descriptor EOL flag updates Finn Thain
2020-01-22 22:07 ` [PATCH net v3 03/12] net/sonic: Use MMIO accessors Finn Thain
2020-01-22 22:07 ` [PATCH net v3 11/12] net/sonic: Fix CAM initialization Finn Thain
2020-01-22 22:07 ` Finn Thain [this message]
2020-01-22 22:07 ` [PATCH net v3 09/12] net/sonic: Quiesce SONIC before re-initializing descriptor memory Finn Thain
2020-01-22 22:07 ` [PATCH net v3 07/12] net/sonic: Improve receive descriptor status flag check Finn Thain
2020-01-22 22:07 ` [PATCH net v3 01/12] net/sonic: Add mutual exclusion for accessing shared state Finn Thain
2020-01-22 22:07 ` [PATCH net v3 05/12] net/sonic: Fix receive buffer handling Finn Thain
2020-01-23 20:24 ` [PATCH net v3 00/12] Fixes for SONIC ethernet driver David Miller

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