Re: [RFC PATCH] usb: host: xhci-sideband: fix deadlock in unregister path

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

On 2/4/26 11:15, Guan-Yu Lin wrote:
> Regarding xhci_sideband_check():
> I have a concern regarding power management with the proposed check:
> 
> if (xhci->devs[i] && xhci->devs[i]->sideband)
>          return true;
> 
> vdev->sideband is assigned during xhci_sideband_register(), which
> happens when the class driver probes (device connection), and it
> persists until disconnect. If we use this check, the xHCI controller
> will be prevented from PM suspending (system suspend) as long as the
> device is connected, even if it is idle (not playing audio).
> For mobile power optimization, we need to allow the controller to
> suspend when the sideband is registered but idle.
> 
> Since we are proceeding with Option B, the class driver will be
> maintaining the udev->offload_usage count via usb_offload_get/put(). I
> propose we still rely on usb_offload_check() (or check offload_usage)
> within the xHCI sideband check. This ensures we only block or adjust
> the PM suspend flow only when there is active data transfer.
Sounds reasonable to me

Thanks
Mathias