Re: FEC on i.MX 7 transmit queue timeout

[Andy Duan <fugang.duan@nxp.com>]

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().
> 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.

Andy