Re: FEC on i.MX 7 transmit queue timeout

[Stefan Agner <stefan@agner.ch>]

On 2017-05-03 20:08, Andy Duan wrote:
> From: Stefan Agner <stefan@agner.ch> Sent: Thursday, May 04, 2017 9:22 AM
>>To: Andy Duan <fugang.duan@nxp.com>
>>Cc: fugang.duan@freescale.com; festevam@gmail.com;
>>netdev@vger.kernel.org; netdev-owner@vger.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.

> 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).

> 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.