Re: [PATCH 2/2] xhci: drop 120ms U3 LFPS wake retry wait from runtime resume

[Lovekesh Solanki <lovekeshsolanki00@gmail.com>]

On Thu, Sep 03, 2026 at 10:42:48AM +0300, Mathias Nyman wrote:
> On 9/2/26 21:21, Lovekesh Solanki wrote:
> > On Wed, Sep 02, 2026 at 03:10:41PM +0300, Mathias Nyman wrote:
> > > It's possible PCI side or pm core already provides some easy way for xhci driver to check this.
> > > This specific issue is currently not on my todo list, yet.
> > Alright, would you like to me to work on this? I could look into
> > that side and possibly come up with an approach.
> 
> Yes, please, that would be great.
I took a look at the PCI / PM side, and it seems to me there isn't any
reliable approach for xhci driver to use right now.

The pci_check_pme_status() both checks and clears the pme status bit 
and the pci core devours it inside pci_pme_wakeup(), and 
pm_request_resume is async so xhci's runtime_resume may run much later
after the bit is already gone. We can't simply export pci_check_pme_status()
that wouldn't give any useful info.

One solution I can think of would be adding a pme_wake_detected bitfield
on pci_dev struct, we set it in pci_pme_wakeup() when PME is confirmed
and we clear it in pci_pm_runtime_resume() after the driver has
returned.
Then, we could directly read via pdev->pme_wake_detected in its own
resume.

What are your thoughts on this?

Regards,
Lovekesh