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

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

On 3/4/26 12:42, Michal Pecio wrote:
> USBSTS is mostly RW1C, so to clear EINT we should write just this
> one bit. Remove pointless code which ORs the bit with current value
> of the register, even though the bit is already known to be set,
> and writes the result back, which clears all active RW1C flags.
> 
> We used to inadvertently clear PCD and SRE in this way. PCD isn't
> used by the driver and SRE is only used at resume, so clearing them
> should make no difference. Don't clear them anymore.
> 
> Tested by connecting and mounting a storage device on a few HCs.
> 
> Before: xhci_irq USBSTS 0x00000018 EINT PCD -> 0x00000000
>          xhci_irq USBSTS 0x00000008 EINT -> 0x00000000
> After:  xhci_irq USBSTS 0x00000018 EINT PCD -> 0x00000010 PCD
>          xhci_irq USBSTS 0x00000018 EINT PCD -> 0x00000010 PCD
> 
> Some flags are RsvdZ - should be written as zero regardless of the
> value read, so technically it was a bug. But no problems are known.
> 

Thanks for cleaning this up.

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

Thanks
Mathias