Re: [REGRESSION] asix: Lots of asix_rx_fixup() errors and slow transmissions

[Guodong Xu]

On 3 May 2016 at 17:23, Dean Jenkins <Dean_Jenkins@xxxxxxxxxx> wrote:
> On 03/05/16 05:55, John Stultz wrote:
>>
>> In testing with HiKey, we found that since commit 3f30b158eba5c60
>> (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.
>>
>> Looking through the commits since the v4.1 kernel where we didn't see
>> this, I narrowed the regression down, and reverting the following two
>> commits seems to avoid the problem:
>>
>> 6a570814cd430fa5ef4f278e8046dcf12ee63f13 asix: Continue processing URB
>> if no RX netdev buffer
>> 3f30b158eba5c604b6e0870027eef5d19fc9271d asix: On RX avoid creating
>> bad Ethernet frames
>>
>> With these reverted, we don't see all the error messages, and we see
>> better ~1.1MB/s throughput (I've got a mouse plugged in, so I think
>> the usb host is only running at "full-speed" mode here).
>>
>> This worries me some, as the patches seem to describe trying to fix
>> the issue they seem to cause, so I suspect a revert isn't the correct
>> solution, but am not sure why we're having such trouble and the patch
>> authors did not.  I'd be happy to do further testing of patches if
>> folks have any ideas.
>>
>> Originally Reported-by: Yongqin Liu <yongqin.liu@xxxxxxxxxx>
>>
>> thanks
>> -john
>
> Hi John,
>
> Some ASIX chipsets span the Ethernet frame over consecutive URBs which
> requires successful transfer of 2 URBs.
>
> This means states of a previous URB influences the processing of the next
> URB including a dropped URB (causes a discontinuity in the data stream). In
> other words synchronisation of the in-band 32-bit header word needs to be
> tracked between URBs. Some ASIX chipsets allow the in-band 32-bit header
> word to be no longer fixed to the start of the URB buffer so it moves to any
> position within the URB buffer.
>
> I understand your point of suggesting it is a "regression" for your device
> but the driver was broken for DUB-E100 C1 (small black USB device). So you
> cannot revert the commits as this would break DUB-E100 C1 (small black USB
> device).
>
>> 6a570814cd430fa5ef4f278e8046dcf12ee63f13 asix: Continue processing URB
>> if no RX netdev buffer
>
> This commit is necessary because it avoids a crash when netdev buffer failed
> to be allocated for the 1st URB and the 2nd URB containing a spanned
> Ethernet frame is processed. The crash happens because the 2nd URB assumed
> that the netdev buffer had been allocated.
>
>> 3f30b158eba5c604b6e0870027eef5d19fc9271d asix: On RX avoid creating
>> bad Ethernet frames
>
> This commit is necessary to avoid sending bad Ethernet frames into the IP
> stack during loss of synchronisation and to dropping good Ethernet frames.
> This commit improves the synchronisation recovery mechanism of the in-band
> 32-bit header word.
>
> The ASIX USB to Ethernet devices these commits were tested on where DUB-E100
> C1 (small black USB device). Embedded ARM based systems were used where
> memory resources can run out.

I don't have the chance to look into detail yet. But just a caution,
did you test on ARM 64-bit system or ARM 32-bit? I ask because HiKey
is an ARM 64-bit system. I suggest we should be careful on that. I saw
similar issues when transferring to a 64-bit system in other net
drivers.

Do you have any suggestion on this regard?

>
> It could be that for your USB to Ethernet device that the wrong
> configuration settings have been used. In other words the ASIX driver is
> flexible to support various variants of the ASIX chipsets. For example, does
> your device support Ethernet frames spanning multiple URBs (multiple USB
> transfers) ?

Would you please suggest how to find out this information? How can I
change my device's configuration settings to support spanning multiple
URBs?

>
> So I doubt my commits are "broken" because we don't see your failures (not
> tested your device). It is more likely that your ASIX device needs to be
> properly identified and configured to be compatible with the ASIX driver. At
> least, I suggest that is the best place to start your investigation.
>
> Of course, your ASIX chipset might have a different behaviour for how the
> in-band 32-bit header word operates so perhaps special treatment is needed
> for your chipset ?
>
> Please send to the mailing list the output of lsusb for your device so that
> people can know the USB product ID and vendor ID for your device. This is
> allows people to assist with the investigation. Do you have any links to
> websites that sell your device ?

I experienced the same issue, working in the same project with John
actually. My USB ID:
Bus 001 Device 003: ID 0b95:772b ASIX Electronics Corp. AX88772B

Link to purchase: http://item.jd.com/1192582.html   (by UGREEN)

John has his own device. And in our lab, there is a third kind of
device which uses the same AX88772B. All purchased from difference
sources with different brand names. And all can reproduce the same
issue.

>
> Are you using UDP or TCP connections ?

In my tests, I use iperf and transfer in TCP mode.

-Guodong

>
> Regards,
> Dean
>
> --
> Dean Jenkins
> Embedded Software Engineer
> Linux Transportation Solutions
> Mentor Embedded Software Division
> Mentor Graphics (UK) Ltd.
>