Hi John,
Thanks for your patch. I think the patch has already been applied.
The git commit subject of
"asix: Fix offset calculation in asix_rx_fixup() causing slow transmissions"
I think is a bit misleading as the bug relates to reception and not
transmission.
I guess that your intent was to say that "the through-put of
communications was low" due to the bug.
Personally, I would of used a git subject like
"asix: Fix asix_rx_fixup_interval() offset calculation for spanned frames"
But anyway, I have no real issue with the patch.
On 17/05/16 04:36, John Stultz wrote:
In testing with HiKey, we found that since
commit 3f30b158eba5 ("asix: On RX avoid creating bad Ethernet
frames"),
we're seeing lots of noise during network transfers:
[ 239.027993] asix 1-1.1:1.0 eth0: asix_rx_fixup() Data Header synchronisation was lost, remaining 988
[ 239.037310] asix 1-1.1:1.0 eth0: asix_rx_fixup() Bad Header Length 0x54ebb5ec, offset 4
[ 239.045519] asix 1-1.1:1.0 eth0: asix_rx_fixup() Bad Header Length 0xcdffe7a2, offset 4
[ 239.275044] asix 1-1.1:1.0 eth0: asix_rx_fixup() Data Header synchronisation was lost, remaining 988
[ 239.284355] asix 1-1.1:1.0 eth0: asix_rx_fixup() Bad Header Length 0x1d36f59d, offset 4
[ 239.292541] asix 1-1.1:1.0 eth0: asix_rx_fixup() Bad Header Length 0xaef3c1e9, offset 4
[ 239.518996] asix 1-1.1:1.0 eth0: asix_rx_fixup() Data Header synchronisation was lost, remaining 988
[ 239.528300] asix 1-1.1:1.0 eth0: asix_rx_fixup() Bad Header Length 0x2881912, offset 4
[ 239.536413] asix 1-1.1:1.0 eth0: asix_rx_fixup() Bad Header Length 0x5638f7e2, offset 4
And network throughput ends up being pretty bursty and slow with
a overall throughput of at best ~30kB/s (where as previously we
got 1.1MB/s with the slower USB1.1 "full speed" host).
We found the issue also was reproducible on a x86_64 system,
using a "high-speed" USB2.0 port but the throughput did not
measurably drop (possibly due to the scp transfer being cpu
bound on my slow test hardware).
After lots of debugging, I found the check added in the
problematic commit seems to be calculating the offset
incorrectly.
In the normal case, in the main loop of the function, we do:
(where offset is zero, or set to "offset += (copy_length + 1) &
0xfffe" in the previous loop)
rx->header = get_unaligned_le32(skb->data +
offset);
offset += sizeof(u32);
But the problematic patch calculates:
offset = ((rx->remaining + 1) & 0xfffe) + sizeof(u32);
rx->header = get_unaligned_le32(skb->data + offset);
Adding some debug logic to check those offset calculation used
to find rx->header, the one in problematic code is always too
large by sizeof(u32).
Thus, this patch removes the incorrect " + sizeof(u32)" addition
in the problematic calculation, and resolves the issue.
Cc: Dean Jenkins <Dean_Jenkins@xxxxxxxxxx>
Cc: "David B. Robins" <linux@xxxxxxxxxxxxxxx>
Cc: Mark Craske <Mark_Craske@xxxxxxxxxx>
Cc: Emil Goode <emilgoode@xxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: YongQin Liu <yongqin.liu@xxxxxxxxxx>
Cc: Guodong Xu <guodong.xu@xxxxxxxxxx>
Cc: Ivan Vecera <ivecera@xxxxxxxxxx>
Cc: linux-usb@xxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx
Cc: stable <stable@xxxxxxxxxxxxxxx> #4.4+
Reported-by: Yongqin Liu <yongqin.liu@xxxxxxxxxx>
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
---
drivers/net/usb/asix_common.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c
index 0c5c22b..7de5ab5 100644
--- a/drivers/net/usb/asix_common.c
+++ b/drivers/net/usb/asix_common.c
@@ -66,7 +66,7 @@ int asix_rx_fixup_internal(struct usbnet *dev, struct sk_buff *skb,
* buffer.
*/
if (rx->remaining && (rx->remaining + sizeof(u32) <= skb->len)) {
- offset = ((rx->remaining + 1) & 0xfffe) + sizeof(u32);
+ offset = ((rx->remaining + 1) & 0xfffe);
I have verified that this fixes my ARM board. Thanks for finding the
mistake.
Note that the outer set of brackets could of been removed as they are
redundant.
rx->header = get_unaligned_le32(skb->data + offset);
offset = 0;
Thanks,
Best regards,
Dean
--
Dean Jenkins
Embedded Software Engineer
Linux Transportation Solutions
Mentor Embedded Software Division
Mentor Graphics (UK) Ltd.
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