mirror of
https://github.com/edk2-porting/linux-next.git
synced 2025-01-17 10:04:14 +08:00
740c7f31c0
Currently we try to clear EDRRR and EDTRR and immediately continue to
free buffers. This is unsafe because:
- In general, register writes are not serialised with DMA, so we still
have to wait for DMA to complete somehow
- The R8A7790 (R-Car H2) manual states that the TX running flag cannot
be cleared by writing to EDTRR
- The same manual states that clearing the RX running flag only stops
RX DMA at the next packet boundary
I applied this patch to the driver to detect DMA writes to freed
buffers:
> --- a/drivers/net/ethernet/renesas/sh_eth.c
> +++ b/drivers/net/ethernet/renesas/sh_eth.c
> @@ -1098,7 +1098,14 @@ static void sh_eth_ring_free(struct net_device *ndev)
> /* Free Rx skb ringbuffer */
> if (mdp->rx_skbuff) {
> for (i = 0; i < mdp->num_rx_ring; i++)
> + memcpy(mdp->rx_skbuff[i]->data,
> + "Hello, world", 12);
> + msleep(100);
> + for (i = 0; i < mdp->num_rx_ring; i++) {
> + WARN_ON(memcmp(mdp->rx_skbuff[i]->data,
> + "Hello, world", 12));
> dev_kfree_skb(mdp->rx_skbuff[i]);
> + }
> }
> kfree(mdp->rx_skbuff);
> mdp->rx_skbuff = NULL;
then ran the loop:
while ethtool -G eth0 rx 128 ; ethtool -G eth0 rx 64; do echo -n .; done
and 'ping -f' toward the sh_eth port from another machine. The
warning fired several times a minute.
To fix these issues:
- Deactivate all TX descriptors rather than writing to EDTRR
- As there seems to be no way of telling when RX DMA is stopped,
perform a soft reset to ensure that both DMA enginess are stopped
- To reduce the possibility of the reset truncating a transmitted
frame, disable egress and wait a reasonable time to reach a
packet boundary before resetting
- Update statistics before resetting
(The 'reasonable time' does not allow for CS/CD in half-duplex
mode, but half-duplex no longer seems reasonable!)
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
|
||
|---|---|---|
| .. | ||
| Kconfig | ||
| Makefile | ||
| sh_eth.c | ||
| sh_eth.h | ||