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net/sonic: Prevent tx watchdog timeout

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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: 1da177e4c3 ("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>
This commit is contained in:
Finn Thain 2020-01-23 09:07:26 +11:00 committed by David S. Miller
parent 772f66421d
commit 686f85d71d
1 changed files with 13 additions and 4 deletions
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17
drivers/net/ethernet/natsemi/sonic.c
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@ -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) {