On Tue, Aug 21, 2007 at 01:33:42AM +0200, Florian Westphal wrote:
> When transferring data at full speed, the DM9000 network interface
> sometimes stops sending/receiving data. Worse, ksoftirqd consumes
> 100% cpu and the net tx watchdog never triggers.
A newline here would have helped readability.
> Fix by spin_lock_irqsave() in dm9000_start_xmit() to prevent the
> interrupt handler from interfering.
I personally have not come across this during any of our testing,
but it is possible that an ARM9 has slightly different interrupt
behaviour to the PXAs.
Changing to use spin_lock_irqsave() is probably a much safer
way of stopping this happening than trying to disable the
interrupts comming from the chip, and spin_lock_irqsave() is
not exactly expensive. This will also stop dm9000_start_xmit from
being interrupted by the watchdog.
I will update my local DM9000 patch set for after the 2.6.23 release.
> Signed-off-by: Florian Westphal <[EMAIL PROTECTED]>
Acked-by: Ben Dooks <[EMAIL PROTECTED]>
> ---
> Actually the comments ('Disable all interrupts, iow(db, DM9000_IMR, IMR_PAR)
> etc)
> give the impression that the interrupt handler cannot run during
> dm9000_start_xmit(),
> however this isn't correct (perhaps the chipset has some weird timing
> issues?).
> The interface lockup usually occurs between 30 and 360 seconds after
> starting transmitting
> data (netcat /dev/zero) at full speed; with this patch applied I haven't
> been able
> to reproduce hangs yet (ran for > 2h).
> FTR: This is a dm9000 on XScale-PXA255 rev 6 (ARMv5TE)/Compulab CM-x255, i.e.
> a module not supported by the vanilla kernel. Tested on (patched) 2.6.18.
>
> dm9000.c | 25 +++++++------------------
> 1 file changed, 7 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/net/dm9000.c b/drivers/net/dm9000.c
> index c3de81b..738aa59 100644
> --- a/drivers/net/dm9000.c
> +++ b/drivers/net/dm9000.c
> @@ -700,6 +700,7 @@ dm9000_init_dm9000(struct net_device *dev)
> static int
> dm9000_start_xmit(struct sk_buff *skb, struct net_device *dev)
> {
> + unsigned long flags;
> board_info_t *db = (board_info_t *) dev->priv;
>
> PRINTK3("dm9000_start_xmit\n");
> @@ -707,10 +708,7 @@ dm9000_start_xmit(struct sk_buff *skb, struct net_device
> *dev)
> if (db->tx_pkt_cnt > 1)
> return 1;
>
> - netif_stop_queue(dev);
> -
> - /* Disable all interrupts */
> - iow(db, DM9000_IMR, IMR_PAR);
> + spin_lock_irqsave(&db->lock, flags);
>
> /* Move data to DM9000 TX RAM */
> writeb(DM9000_MWCMD, db->io_addr);
> @@ -718,12 +716,9 @@ dm9000_start_xmit(struct sk_buff *skb, struct net_device
> *dev)
> (db->outblk)(db->io_data, skb->data, skb->len);
> db->stats.tx_bytes += skb->len;
>
> + db->tx_pkt_cnt++;
> /* TX control: First packet immediately send, second packet queue */
> - if (db->tx_pkt_cnt == 0) {
> -
> - /* First Packet */
> - db->tx_pkt_cnt++;
> -
> + if (db->tx_pkt_cnt == 1) {
> /* Set TX length to DM9000 */
> iow(db, DM9000_TXPLL, skb->len & 0xff);
> iow(db, DM9000_TXPLH, (skb->len >> 8) & 0xff);
> @@ -732,23 +727,17 @@ dm9000_start_xmit(struct sk_buff *skb, struct
> net_device *dev)
> iow(db, DM9000_TCR, TCR_TXREQ); /* Cleared after TX complete */
>
> dev->trans_start = jiffies; /* save the time stamp */
> -
> } else {
> /* Second packet */
> - db->tx_pkt_cnt++;
> db->queue_pkt_len = skb->len;
> + netif_stop_queue(dev);
> }
>
> + spin_unlock_irqrestore(&db->lock, flags);
> +
> /* free this SKB */
> dev_kfree_skb(skb);
>
> - /* Re-enable resource check */
> - if (db->tx_pkt_cnt == 1)
> - netif_wake_queue(dev);
> -
> - /* Re-enable interrupt */
> - iow(db, DM9000_IMR, IMR_PAR | IMR_PTM | IMR_PRM);
> -
> return 0;
> }
If I read this correctly, you've moved the netif_{stop,start}_queue()
calls so that the queue is only stopped if we have loaded 2 packets
into the chip instead of stopping and starting each time.
> -
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--
Ben ([EMAIL PROTECTED], http://www.fluff.org/)
'a smiley only costs 4 bytes'
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