Re: [PATCH] usb: xhci: Simplify clearing the Event Interrupt bit

[Michal Pecio <michal.pecio@gmail.com>]

On Thu, 19 Mar 2026 22:33:49 +0200, Mathias Nyman wrote:
> Leaving the Port Change Detectd (PCD) bit uncleared worries me a bit.
> Did suspend and resume still work properly after this?
> especially something like wakeup from suspend (D3) on usb port connect

The bit seems to only be mentioned in 5.4.2 and 4.15.2.3, with no
indication that it's supposed to have any effect on HW behavior.

And I found no occurences of STS_PORT outside xhci.h.


But to be sure, I tested resuming by connection today.

Chipset xHCI and a PCIe card with Etron are fully functional.

NEC wakes from S3 but not s2idle, also if waking with a keyboard.
Maybe a HW bug: expects absence of core power.

Several other cards (VL805, FL1100, uPD720202, ASM1142, ASM3142) wake
from s2idle but not S3, including with a keyboard.

No difference if this patch is reverted, no difference if PCD is
explicitly cleared in xhci_suspend(). And same problem in Windows.
Looks like a HW deficiency in those cards.


I also ran into this problem (and applied the patch):
https://lore.kernel.org/linux-usb/20260316094811.1559471-1-xu.yang_2@nxp.com/