Commit 74389183 authored Jan 23, 2020 by Finn Thain Committed by Greg Kroah-Hartman Jan 29, 2020

net/sonic: Prevent tx watchdog timeout



commit 686f85d71d095f1d26b807e23b0f0bfd22042c45 upstream.

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: 1da177e4 ("Linux-2.6.12-rc2")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 58c0c4b1

drivers/net/ethernet/natsemi/sonic.c

+13 −4

Original line number	Diff line number	Diff line
		@@ -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) {