Re: xHCI host dies on device unplug

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 15.12.2022 18.12, Ladislav Michl wrote:
> +Cc Mathias as he last touched this code path and may know more :)
> 
> On Tue, Dec 06, 2022 at 02:17:08PM +0100, Ladislav Michl wrote:
>> On Mon, Dec 05, 2022 at 10:27:57PM +0100, Ladislav Michl wrote:
>>> I'm running current linux.git on custom Marvell OCTEON III CN7020
>>> based board. USB devices like FTDI (idVendor=0403, idProduct=6001,
>>> bcdDevice= 6.00) Realtek WiFi dongle (idVendor=0bda, idProduct=8179,
>>> bcdDevice= 0.00) works without issues, while Ralink WiFi dongle
>>> (idVendor=148f, idProduct=5370, bcdDevice= 1.01) kills the host on
>>> disconnect:
>>> xhci-hcd xhci-hcd.0.auto: xHCI host not responding to stop endpoint command
>>> xhci-hcd xhci-hcd.0.auto: xHCI host controller not responding, assume dead
>>> xhci-hcd xhci-hcd.0.auto: HC died; cleaning up
>>>
>>> Unfortunately I do not have a datasheet for CN7020 SoC, so it is hard
>>> to tell if there is any errata :/ In case anyone see a clue in debug
>>> logs bellow, I'll happily give it a try.
>>
>> So I do have datasheet now. As a wild guess I tried to use dlmc_ref_clk0
>> instead of dlmc_ref_clk1 as a refclk-type-ss and it fixed unplug death.
>> I have no clue why, but anyway - sorry for the noise :) Perhaps Octeon's
>> clock init is worth to be verified...
> 
> After all whenever xhci dies with "xHCI host not responding to stop endpoint
> command" depends also on temperature, so there seems to be race somewhere.
> 
> As a quick and dirty verification, whenever xhci really died, following patch
> was tested and it fixed issue. It just treats ep as if stop endpoint command
> succeeded. Any clues? I'll happily provide more traces.

It's possible the controller did complete the stop endpoint command but driver
didn't get the interrupt for the event for some reason.

I wrote some patches that checks the event ring for this event during
timeout.

code is in a stop_endpoint_fixes branch in my tree:

git://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git stop_endpoint_fixes
https://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git/log/?h=stop_endpoint_fixes

Another thing would be checking command and event rings for this stop endpoint command.
So Instead of killing host at timeout, do nothing, and check sysfs after the disconnect:

cat /sys/kernel/debug/usb/xhci/<address>/event-ring/trbs
cat /sys/kernel/debug/usb/xhci/<address>/command-ring/trbs

-Mathias