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

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

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.
  
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