Date:   Wed, 19 Apr 2017 16:15:22 -0700
From:   Stefan Agner <stefan@...er.ch>
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

On 2017-04-19 01:45, Andy Duan wrote:
> On 2017年04月19日 13:56, Stefan Agner wrote:
>> On 2017-04-18 22:28, Andy Duan wrote:
>>> From: Stefan Agner <stefan@...er.ch> Sent: Wednesday, April 19, 2017 1:02 PM
>>>> 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 2017-04-18 19:24, Andy Duan wrote:
>>>>> On 2017年04月19日 03:46, Stefan Agner wrote:
>>>>>> Hi,
>>>>>>
>>>>>> I noticed last week on upstream (v4.11-rc6) on a Colibri iMX7 board
>>>>>> that after a while (~10 minutes) the detdev wachdog prints a
>>>>>> stacktrace and the driver then continuously dumps the TX ring. I then
>>>>>> did a quick test with 4.10, and realized it actually suffers the same
>>>>>> issue, so it seems not to be a regression. I use a rootfs mounted over NFS...
>>>>>>
>>>>>> ------------[ cut here ]------------
>>>>>> WARNING: CPU: 0 PID: 0 at net/sched/sch_generic.c:316
>>>>>> dev_watchdog+0x240/0x244
>>>>>> NETDEV WATCHDOG: eth0 (fec): transmit queue 2 timed out Modules
>>>>>> linked in:
>>>>>> CPU: 0 PID: 0 Comm: swapper/0 Not tainted
>>>>>> 4.11.0-rc7-00030-g2c4e6bd0c4f0-dirty #330 Hardware name: Freescale
>>>>>> i.MX7 Dual (Device Tree) [<c02293f0>] (unwind_backtrace) from
>>>>>> [<c0225820>] (show_stack+0x10/0x14) [<c0225820>] (show_stack) from
>>>>>> [<c050db6c>] (dump_stack+0x90/0xa0) [<c050db6c>] (dump_stack) from
>>>>>> [<c023ae68>] (__warn+0xac/0x11c) [<c023ae68>] (__warn) from
>>>>>> [<c023af10>] (warn_slowpath_fmt+0x38/0x48) [<c023af10>]
>>>>>> (warn_slowpath_fmt) from [<c088bb8c>]
>>>>>> (dev_watchdog+0x240/0x244)
>>>>>> [<c088bb8c>] (dev_watchdog) from [<c0294798>]
>>>>>> (run_timer_softirq+0x24c/0x708)
>>>>>> [<c0294798>] (run_timer_softirq) from [<c023f584>]
>>>>>> (__do_softirq+0x12c/0x2a8)
>>>>>> [<c023f584>] (__do_softirq) from [<c023f8c4>] (irq_exit+0xdc/0x13c)
>>>>>> [<c023f8c4>] (irq_exit) from [<c02818ac>]
>>>>>> (__handle_domain_irq+0xa4/0xf8)
>>>>>> [<c02818ac>] (__handle_domain_irq) from [<c0201624>]
>>>>>> (gic_handle_irq+0x34/0xa4)
>>>>>> [<c0201624>] (gic_handle_irq) from [<c0226338>] (__irq_svc+0x58/0x8c)
>>>>>> Exception stack(0xc1201f30 to 0xc1201f78)
>>>>>> 1f20:                                     c0233320 00000000 00000000
>>>>>> 01400000
>>>>>> 1f40: c1203d80 ffffe000 00000000 00000000 c107bf10 c0e055b5 c1203d34
>>>>>> 00000001
>>>>>> 1f60: c07d2324 c1201f80 c0222ac8 c0222acc 60000013 ffffffff
>>>>>> [<c0226338>] (__irq_svc) from [<c0222acc>] (arch_cpu_idle+0x38/0x3c)
>>>>>> [<c0222acc>] (arch_cpu_idle) from [<c0275f24>] (do_idle+0xa8/0x250)
>>>>>> [<c0275f24>] (do_idle) from [<c02760e4>]
>>>>>> (cpu_startup_entry+0x18/0x1c) [<c02760e4>] (cpu_startup_entry) from
>>>>>> [<c1000aa0>]
>>>>>> (start_kernel+0x3fc/0x45c)
>>>>>> ---[ end trace 5b0c6dc3466a7918 ]---
>>>>>> fec 30be0000.ethernet eth0: TX ring dump
>>>>>> Nr     SC     addr       len  SKB
>>>>>>     0    0x1c00 0x00000000  590   (null)
>>>>>>     1    0x1c00 0x00000000  590   (null)
>>>>>>     2    0x1c00 0x00000000   42   (null)
>>>>>>     3  H 0x1c00 0x00000000   42   (null)
>>>>>>     4 S  0x0000 0x00000000    0   (null)
>>>>>>     5    0x0000 0x00000000    0   (null)
>>>>>>     6    0x0000 0x00000000    0   (null)
>>>>>>     7    0x0000 0x00000000    0   (null)
>>>>>>     8    0x0000 0x00000000    0   (null)
>>>>>>     9    0x0000 0x00000000    0   (null)
>>>>>>    10    0x0000 0x00000000    0   (null)
>>>>>>    11    0x0000 0x00000000    0   (null)
>>>>>>    12    0x0000 0x00000000    0   (null)
>>>>>>    13    0x0000 0x00000000    0   (null)
>>>>>>    14    0x0000 0x00000000    0   (null)
>>>>>>    15    0x0000 0x00000000    0   (null)
>>>>>>    16    0x0000 0x00000000    0   (null)
>>>>>>    17    0x0000 0x00000000    0   (null)
>>>>>>    18    0x0000 0x00000000    0   (null)
>>>>>> ...
>>>>>>
>>>>>>
>>>>>> A second TX ring dump from 4.10:
>>>>>> fec 30be0000.ethernet eth0: TX ring dump
>>>>>> Nr     SC     addr       len  SKB
>>>>>>     0    0x1c00 0x00000000   42   (null)
>>>>>>     1    0x1c00 0x00000000   42   (null)
>>>>>>     2    0x1c00 0x00000000   90   (null)
>>>>>>     3    0x1c00 0x00000000   90   (null)
>>>>>>     4    0x1c00 0x00000000   90   (null)
>>>>>>     5    0x1c00 0x00000000  218   (null)
>>>>>>     6    0x1c00 0x00000000  218   (null)
>>>>>>     7    0x1c00 0x00000000  218   (null)
>>>>>>     8    0x1c00 0x00000000   90   (null)
>>>>>>     9    0x1c00 0x00000000  206   (null)
>>>>>>    10    0x1c00 0x00000000  216   (null)
>>>>>>    11    0x1c00 0x00000000  216   (null)
>>>>>>    12    0x1c00 0x00000000  216   (null)
>>>>>>    13    0x1c00 0x00000000  311   (null)
>>>>>>    14    0x1c00 0x00000000  178   (null)
>>>>>>    15    0x1c00 0x00000000  311   (null)
>>>>>>    16    0x1c00 0x00000000  206   (null)
>>>>>>    17  H 0x1c00 0x00000000  311   (null)
>>>>>>    18 S  0x0000 0x00000000    0   (null)
>>>>>>    19    0x0000 0x00000000    0   (null)
>>>>> The dump show tx ring is fine.
>>>>>
>>>>>> The ring dump prints continously, but I can access console every now
>>>>>> and then. I noticed that the second interrupt seems static (66441, TX
>>>>>> interrupt?):
>>>>>>    58:         18     GIC-0 150 Level     30be0000.ethernet
>>>>>>    59:      66441     GIC-0 151 Level     30be0000.ethernet
>>>>>>    60:      70477     GIC-0 152 Level     30be0000.ethernet
>>>>> 150 irq number is for tx/rx queue 1 receive/transmit buffer/frame done.
>>>>> 151 irq number is for tx/rx queue 2 receive/transmit buffer/frame done.
>>>>> 152 irq number is for tx/rx queue 0 receive/transmit buffer/frame
>>>>> done, mii interrupt and others.
>>>>>
>>>>> i.MX7D enet has three queues for tx and rx.
>>>>> It seems netdev pick tx queue 1 rate is very rare by __netdev_pick_tx().
>>>> Oh ok I see, and it seems to choose queue 2 fairly often...
>>>>
>>>>>> Anybody else seen this? Any idea?
>>>>>>
>>>>>> In 4.10 as well as 4.11-rc6 the interrupt counts were just over 65536...
>>>>>> pure chance?
>>>>>>
>>>>>>
>>>>> you can use ethtool to set the irq coalesce like:
>>>>> ethtool -c eth0 rx-frames 80
>>>>> ethtool -c eth0 rx-usecs 600
>>>>> ethtool -c eth0 tx-frames 64
>>>>> ethtool -c eth0 tx-usenc 700
>>>>>
>>>>>
>>>>> You don't run any test case, just nfs mount rootfs ?
>>>>> I will setup one imx7d sdb board to run it.
>>>> I noticed it without doing anything, just boot via NFS. There was always a little
>>>> bit of activity, at least according to the link (blinks every ~5s).
>>>>
>>>> It seemd that it happened a bit earlier when using iperf to exacerbate the
>>>> problem...
>>>>
>>>> I noticed that errata 7885 is not mentioned in the i.MX 7 errata, so I created a
>>>> new devtype:
>>>>
>>>>         }, {
>>>>                 .name = "imx7d-fec",
> This is added by you, we never added the platform_device_id.
> 
>>>>                 .driver_data = FEC_QUIRK_ENET_MAC | FEC_QUIRK_HAS_GBIT |
>>>>                                 FEC_QUIRK_HAS_BUFDESC_EX | FEC_QUIRK_HAS_CSUM |
>>>>                                 FEC_QUIRK_HAS_VLAN | FEC_QUIRK_BUG_CAPTURE |
>>>>                                 FEC_QUIRK_HAS_RACC | FEC_QUIRK_HAS_COALESCE,
>>>>         }, {
>>>>
>>> Upstreaming driver doesn't have the platform_device_id for
>>> "imx7d-fec", imx7d enet still use imx6sx-fec device id driver.
>>> It lost FEC_QUIRK_ERR007885 and FEC_QUIRK_HAS_AVB quirk flags.
>> Also downstream uses imx6sx-fec, at least 4.1.15 GA 2.0.0 release:
>> http://git.freescale.com/git/cgit.cgi/imx/linux-imx.git/tree/arch/arm/boot/dts/imx7d.dtsi?h=imx_4.1.15_2.0.0_ga#n1380
>>
>> However, with downstream Linux 4.1 the kernel seems to only use queue 0:
>> 292:          0     GPCV2 118 Edge      30be0000.ethernet
>> 293:          0     GPCV2 119 Edge      30be0000.ethernet
>> 294:     204929     GPCV2 120 Edge      30be0000.ethernet
>>
> yes, queue 0 is for best effort, queue 1 and 2 are for audio/video.
> 
>>> You can add these.
>> I guess if i.MX 7 does not suffer ERR007885 it would be good to add a
>> new devtype, correct? This also needs a device tree change, since
>> imx6sx-fec is still in the compatible list... I saw that you sent a
>> patch to add ERR007885 for imx6ul as well ("net: fec: add ERR007885 for
>> i.MX6ul enet IP").
> ERR007885 just to add some cycles before set TDAR that don't take side 
> effort.
> I will confirm the hw issue is fixed or not.
> 
>> My earlier run which showed the stack trace again actually still had
>> imx6sx-fec in the device tree compatible string, and hence used
>> ERR007885! So I need to test again...
>>
> pls use compatible string "imx6sx-fec" and test again.
> 

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.

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:

(I do not have the first dump unfortunately)
fec 30be0000.ethernet eth0: TX ring dump
Nr     SC     addr       len  SKB
  0  H 0x1c00 0x00000000   78   (null)
  1 S  0x0000 0x00000000   66   (null)
  2    0x0000 0x00000000   78   (null)
  3    0x0000 0x00000000   78   (null)
  4    0x0000 0x00000000   78   (null)
...



>>> I validate imx7d sdb board with 4.11.0-rc6, no such problem after nfs
>>> mount more than 3.5 hours
>> Hm, the Colibri iMX7 uses a different PHY and only supports fast
>> ethernet. Also, I do tests on a i.MX 7Solo actually, but I can do test
>> on a i.MX 7Dual tomorrow. But again, with downstream which only uses
>> queue 0 the issue did never appear.
>>
>> --
> no, my imx7d sdb board running upstreaming kernel 4.11.0-rc6 with three 
> queues.
> So far so good (about 6.5 hours).


--
Stefan

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