Re: [PATCH net-next v3 5/7] usbnet: smsc95xx: Forward PHY interrupts to PHY driver to avoid polling

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hi Lukas,

On 26.08.2022 09:19, Lukas Wunner wrote:
> On Fri, Aug 26, 2022 at 08:51:58AM +0200, Marek Szyprowski wrote:
>> On 19.05.2022 23:22, Marek Szyprowski wrote:
>>> On 19.05.2022 21:08, Lukas Wunner wrote:
>>>> On Tue, May 17, 2022 at 12:18:45PM +0200, Marek Szyprowski wrote:
>>>>> This patch landed in the recent linux next-20220516 as commit
>>>>> 1ce8b37241ed ("usbnet: smsc95xx: Forward PHY interrupts to PHY
>>>>> driver to
>>>>> avoid polling"). Unfortunately it breaks smsc95xx usb ethernet
>>>>> operation
>>>>> after system suspend-resume cycle. On the Odroid XU3 board I got the
>>>>> following warning in the kernel log:
>>>>>
>>>>> # time rtcwake -s10 -mmem
>>>>> rtcwake: wakeup from "mem" using /dev/rtc0 at Tue May 17 09:16:07 2022
>>>>> PM: suspend entry (deep)
>>>>> Filesystems sync: 0.001 seconds
>>>>> Freezing user space processes ... (elapsed 0.002 seconds) done.
>>>>> OOM killer disabled.
>>>>> Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
>>>>> printk: Suspending console(s) (use no_console_suspend to debug)
>>>>> smsc95xx 4-1.1:1.0 eth0: entering SUSPEND2 mode
>>>>> smsc95xx 4-1.1:1.0 eth0: Failed to read reg index 0x00000114: -113
>>>>> smsc95xx 4-1.1:1.0 eth0: Error reading MII_ACCESS
>>>>> smsc95xx 4-1.1:1.0 eth0: __smsc95xx_mdio_read: MII is busy
>>>>> ------------[ cut here ]------------
>>>>> WARNING: CPU: 2 PID: 73 at drivers/net/phy/phy.c:946
>>>>> phy_state_machine+0x98/0x28c
>>>> [...]
>>>>> It looks that the driver's suspend/resume operations might need some
>>>>> adjustments. After the system suspend/resume cycle the driver is not
>>>>> operational anymore. Reverting the $subject patch on top of linux
>>>>> next-20220516 restores ethernet operation after system suspend/resume.
>>>> Thanks a lot for the report. It seems the PHY is signaling a link
>>>> change
>>>> shortly before system sleep and by the time the phy_state_machine()
>>>> worker
>>>> gets around to handle it, the device has already been suspended and thus
>>>> refuses any further USB requests with -EHOSTUNREACH (-113):
> [...]
>>>> Assuming the above theory is correct, calling phy_stop_machine()
>>>> after usbnet_suspend() would be sufficient to fix the issue.
>>>> It cancels the phy_state_machine() worker.
>>>>
>>>> The small patch below does that. Could you give it a spin?
>>> That's it. Your analysis is right and the patch fixes the issue. Thanks!
>>>
>>> Feel free to add:
>>>
>>> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>>
>>> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
>> Gentle ping for the final patch...
> Hm?  Actually this issue is supposed to be fixed by mainline commit
> 1758bde2e4aa ("net: phy: Don't trigger state machine while in suspend").
>
> The initial fix attempt that you're replying to should not be necessary
> with that commit.
>
> Are you still seeing issues even with 1758bde2e4aa applied?
> Or are you maybe using a custom downstream tree which is missing that commit?

On Linux next-20220825 I still get the following warning during 
suspend/resume cycle:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 1483 at drivers/net/phy/phy_device.c:323 
mdio_bus_phy_resume+0x10c/0x110
Modules linked in: exynos_gsc s5p_jpeg s5p_mfc videobuf2_dma_contig 
v4l2_mem2mem videobuf2_memops videobuf2_v4l2 videobuf2_common videodev 
mc s5p_cec
CPU: 0 PID: 1483 Comm: rtcwake Not tainted 6.0.0-rc2-next-20220825 #5482
Hardware name: Samsung Exynos (Flattened Device Tree)
  unwind_backtrace from show_stack+0x10/0x14
  show_stack from dump_stack_lvl+0x58/0x70
  dump_stack_lvl from __warn+0xc8/0x220
  __warn from warn_slowpath_fmt+0x5c/0xb4
  warn_slowpath_fmt from mdio_bus_phy_resume+0x10c/0x110
  mdio_bus_phy_resume from dpm_run_callback+0x94/0x208
  dpm_run_callback from device_resume+0x124/0x21c
  device_resume from dpm_resume+0x108/0x278
  dpm_resume from dpm_resume_end+0xc/0x18
  dpm_resume_end from suspend_devices_and_enter+0x208/0x70c
  suspend_devices_and_enter from pm_suspend+0x364/0x430
  pm_suspend from state_store+0x68/0xc8
  state_store from kernfs_fop_write_iter+0x110/0x1d4
  kernfs_fop_write_iter from vfs_write+0x1c4/0x2ac
  vfs_write from ksys_write+0x5c/0xd4
  ksys_write from ret_fast_syscall+0x0/0x1c
Exception stack(0xf2ee5fa8 to 0xf2ee5ff0)
5fa0:                   00000004 0002b438 00000004 0002b438 00000004 
00000000
5fc0: 00000004 0002b438 000291b0 00000004 0002b438 00000004 befd9c1c 
00028160
5fe0: 0000006c befd9ae8 b6eb4148 b6f118a4
irq event stamp: 58381
hardirqs last  enabled at (58393): [<c019ff28>] vprintk_emit+0x320/0x344
hardirqs last disabled at (58400): [<c019fedc>] vprintk_emit+0x2d4/0x344
softirqs last  enabled at (58258): [<c0101694>] __do_softirq+0x354/0x618
softirqs last disabled at (58247): [<c012dd18>] __irq_exit_rcu+0x140/0x1ec
---[ end trace 0000000000000000 ]---

The mentioned patch fixes it.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland