Re: xHCI host dies on device unplug

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

On 20.12.2022 9.58, Ladislav Michl wrote:
> On Mon, Dec 19, 2022 at 10:45:43PM +0100, Ladislav Michl wrote:
>> On Mon, Dec 19, 2022 at 07:31:02PM +0100, Ladislav Michl wrote:
>>> On Mon, Dec 19, 2022 at 02:25:46PM +0200, Mathias Nyman wrote:
>>>> Looks like controller didn't complete the stop endpoint command.
>>>>
>>>> Event for last completed command (before cycle bit change "c" -> "C") was:
>>>>    0x00000000028f55a0: TRB 00000000035e81a0 status 'Success' len 0 slot 1 ep 0 type 'Command Completion Event' flags e:c,
>>>>
>>>> This was for command at 35e81a0, which in the command ring was:
>>>>    0x00000000035e81a0: Reset Endpoint Command: ctx 0000000000000000 slot 1 ep 3 flags T:c
>>>>
>>>> The stop endpoint command was the next command queued, at 35e81b0:
>>>>    0x00000000035e81b0: Stop Ring Command: slot 1 sp 0 ep 3 flags c
>>>>
>>>> There were a lot of URBs queued for this device, and they are cancelled one by one after disconnect.
>>>>
>>>> Was this the only device connected? If so does connecting another usb device to another root port help?
>>>> Just to test if the host for some reason partially stops a while after last device disconnect?
>>>
>>> Device is connected directly into SoC. Once connected into HUB, host doesn't die
>>> (as noted in other email, sorry for not replying to my own message, so it got lost)
>>> It seems as intentional (power management?) optimization. If another device is
>>> plugged in before 5 sec timeout expires, host completes stop endpoint command.
>>>
>>> Unfortunately I cannot find anything describing this behavior in
>>> documentation, so I'll ask manufacturer support.
>>
>> As support is usually slow I asked search engine first and this sounds
>> familiar:
>> "Synopsis Designware USB3 IP earlier than v3.00a which is configured in silicon
>> with DWC_USB3_SUSPEND_ON_DISCONNECT_EN=1, would need a specific quirk to prevent
>> xhci host controller from dying when device is disconnected."
>>
>> usb: dwc3: Add quirk for Synopsis device disconnection errata
>> https://patchwork.kernel.org/project/linux-omap/patch/1424151697-2084-5-git-send-email-Sneeker.Yeh@tw.fujitsu.com/
>>
>> Any clue what happened with that? I haven't found any meaningfull traces...
> 
> Just for completeness, this turned into:
> 41135de1e7fd ("usb: xhci: add quirk flag for broken PED bits")
> and it is enabled:
> cc params 0x0220f065 hci version 0x100 quirks 0x0000000002010010
> 
> However I do not see original logic there, clearing PORT_CSC before
> stopping endpoint.

CSC is cleared to allow xHC future port change events reporting.
we don't want to miss when something is re-connected.

Hardware shouldn't stop running based on cleared CSC, it should stop when
driver clears the USBCMD register Run/Stop bit.

-Mathias