netdev - Re: FEC on i.MX 7 transmit queue timeout

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Message-ID: <110a7a48649cfcbbee46340c230e9008@agner.ch>
Date:   Thu, 04 May 2017 19:09:45 -0700
From:   Stefan Agner <stefan@...er.ch>
To:     Andy Duan <fugang.duan@....com>
Cc:     festevam@...il.com, netdev@...r.kernel.org,
        netdev-owner@...r.kernel.org
Subject: Re: FEC on i.MX 7 transmit queue timeout

On 2017-05-04 19:03, Andy Duan wrote:
> On 2017年05月05日 05:36, Stefan Agner wrote:
>> On 2017-05-03 20:08, Andy Duan wrote:
>>> From: Stefan Agner <stefan@...er.ch> Sent: Thursday, May 04, 2017 9:22 AM
>>>> To: Andy Duan <fugang.duan@....com>
>>>> Cc: fugang.duan@...escale.com; festevam@...il.com;
>>>> netdev@...r.kernel.org; netdev-owner@...r.kernel.org
>>>> Subject: Re: FEC on i.MX 7 transmit queue timeout
>>>>
>>>> Hi Andy,
>>>>
>>>> On 2017-04-20 19:48, Andy Duan wrote:
>>>>> On 2017年04月20日 07:15, Stefan Agner wrote:
>>>>>> I tested again with imx6sx-fec compatible string. I could reproduce
>>>>>> it on a Colibri with i.MX 7Dual. But not always: It really depends
>>>>>> whether queue 2 is counting up or not. Just after boot, I check
>>>>>> /proc/interrupts twice, if queue 2 is counting it will happen!
>>>>>>
>>>>>> But if only queue 0 is mostly in use, then it seems to work just fine.
>>>>> If your case is only running best effort like tcp/udp, you can re-set
>>>>> the "fsl,num-tx-queues" and "fsl,num-rx-queues" to 1 in board dts file.
>>>>> Other two queues are for AVB audio/video queues, they have high
>>>>> priority than queue 0. If running iperf tcp test on the three queues,
>>>>> then the tcp segment may be out-of-order that cause net watchdog
>>>> timeout.
>>>>>> I also tried i.MX 7Dual SabreSD here, and the same thing. I had to
>>>>>> reboot 3 times, then queue 2 was counting:
>>>>>>    57:          8     GIC-0 150 Level     30be0000.ethernet
>>>>>>    58:      20137     GIC-0 151 Level     30be0000.ethernet
>>>>>>    59:       9269     GIC-0 152 Level     30be0000.ethernet
>>>>>>
>>>>>> It took me about 40 minutes on Sabre until it happened, and I had to
>>>>>> force it using iperf, but then I got the ring dumps:
>>>>> My board had ran more than 47 hours with nfs rootfs in 4.11.0-rc6, but
>>>>> not running iperf.
>>>>> I am testing with iperf.
>>>> Any update on this issue?
>>>>
>>>> When using iperf (server) on the board with Linux 4.11 the issue appears
>>>> within a few iperf iterations on a Sabre (TO 1.2, Board Rev C, if that matters)...
>>>>
>>> I don’t know whether you received my last mail. (maybe failed due to I
>>> received some rejection mails)
>> I think I did not... The last email I received was Fri, 21 Apr 2017
>> 02:48:23 UTC.
>>
>>
>>> If your case is only running best effort like tcp/udp, you can re-set
>>> the "fsl,num-tx-queues" and "fsl,num-rx-queues" to 1 in board dts
>>> file.
>> I did test that, and it seems to work fine with those properties set to
>> 1.
> So it can fix your problem after long time test?

Yes, seems to work fine after more than 2 hours.

>>> Other two queues are for AVB audio/video queues, they have high
>>> priority than queue 0. If running iperf tcp test on the three queues,
>>> then the tcp segment may be out-of-order that cause net watchdog
>>> timeout.
>> Okay. A single event would be understandable, but it seems to enter some
>> kind of loop after that (continuously printing "fec 30be0000.ethernet
>> eth0: TX ring dump ...").
>>
>> In a quick test I commented out the fec_dump call, with that it seems to
>> print only once and continues working afterwards (although, speed starts
>> to decrease, so something is not good at that point).
> The test base on above change ? One queue still bring watchdog timeout ?

No, sorry for the confusion: This was without the fix above. So use
multiple queues, and disable fec_dump... I was just wondering, because
disabling the multiple queues seems to me somewhat a workaround for
now... :-)

--
Stefan

>>> In fsl kernel tree, there have one patch that only select the queue0
>>> for best effort like tcp/udp. Pls test again in your board, if no
>>> problem I will upstream the patch.
>> That sounds like a reasonable fix.
>>
>> IP, no matter whether TCP/UDP, is the most common use case, so IMHO this
>> should "just work" by default.
>>
>> --
>> Stefan