Re: [REGRESSION 6.16] xHCI host not responding to stop endpoint command after suspend and resume

["Neronin, Niklas" <niklas.neronin@linux.intel.com>]

On 19/08/2025 11.56, Mathias Nyman wrote:
> On 19.8.2025 9.41, Michał Pecio wrote:
>> On Mon, 18 Aug 2025 23:11:03 +0200, Michał Pecio wrote:
>>> A bisect effort is ongoing and c0c9379f235d ("Merge tag 'usb-6.16-rc1'
>>> of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb") is bad,
>>> so that's where the bug likely came from.
>>
>> Looks like the result is in.
>>
>> e1db856bd28891d70008880d7f1d3b8d1ea948fd is the first bad commit
>> commit e1db856bd28891d70008880d7f1d3b8d1ea948fd
>> Author: Niklas Neronin <niklas.neronin@linux.intel.com>
>> Date:   Thu May 15 16:56:14 2025 +0300
>>
>>      usb: xhci: remove '0' write to write-1-to-clear register
> 
> Thanks for tracking this down, I see the issue now
> 
> We may lose interrupts due to this patch, example:
> 
> Hardware sets IMAN_IP BIT(0) when in needs attention
> Driver later allows xHC interrupt by setting IMAN_IE BIT(1), but
> Driver clears IMAN_IP (RW1C) when setting IMAN_IE so no interrupt is triggered.

Apologies for my blunder.

So, there can be an interrupt pending even when the interrupt is not enabled?
But there (ideally) should not be an interrupt pending when disabling the interrupt?

I can submit a fix patch.

Best regards,
Niklas

>  
> interrupts are only triggered if both IMAN_IE and IMAN_IP are set, (and some other
> moderation and event handling bits are correct)
> 
> we need to make sure we don't accidentally clear a pending interrupt (IMAN_IP)
> in both the enable and disable case.
> 
> Thanks
> Mathias
> 
>