Re: [PATCH v5] usb: pci-quirks: always assert xHCI OS ownership

[Michal Pecio]

On Mon, 12 Oct 2026 15:14:14 -0500, Mario Limonciello wrote:
> On 9/2/26 00:39, Rishabh Jain wrote:
> > The xHCI ownership protocol requires the OS driver to assert the HC OS
> > Owned semaphore before using the host controller, then wait for HC BIOS
> > Owned to clear if firmware owns it.
> > 
> > quirk_usb_handoff_xhci() currently asserts OS Owned only when BIOS Owned
> > is already set. If firmware leaves BIOS Owned clear, Linux uses the xHC
> > while both ownership semaphores remain clear.
> > 
> > The timeout fallback also clears BIOS Owned using the original register
> > value, which can clear OS Owned at the same time.
> > 
> > On an AMD PROM21 xHCI controller (1022:43fc), this caused every S3
> > resume to terminate Controller Restore State with USBSTS 0x401. Linux
> > then reset the host controller, both root hubs and the USB Bluetooth
> > adapter.
> > 
> > The controller entered resume ready and halted with USBSTS 0x1.
> > Endpoint state, 100 ms save/restore delays, scratchpads, the DCBAA,
> > device contexts and command, event and transfer rings were verified not
> > to cause the restore error.
> > 
> > Across four S3 cycles, asserting only HC OS Owned changed USBLEGSUP from
> > 0x00000801 to 0x01000801 and eliminated the restore failure. Testing
> > included the unmodified 7.1.8-ogc1.1.fc44.x86_64 distribution kernel
> > using a test module that set the HC OS Owned semaphore. The same test
> > was repeated after review with the same result. Clearing USBLEGCTLSTS
> > was independently verified to be unnecessary.
> > 
> > Always assert OS Owned for controllers using the standard xHCI handoff,
> > and leave the existing TI/Renesas forced handoff unchanged. Keep OS
> > Owned asserted after the standard handoff, including when forcing BIOS
> > Owned clear after a timeout, to prevent firmware from reclaiming the
> > controller during subsequent suspends.
> > 
> > Fixes: 66d4eadd8d06 ("USB: xhci: BIOS handoff and HW initialization.")
> > Cc: stable@xxxxxxxxxxxxxxx
> > Assisted-by: LLM
> > Signed-off-by: Rishabh Jain <rishabh.jain1198@xxxxxxxxx>
> > ---  
> 
> Reviewed-by: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>

Yes, this fixes a legit issue and would be worth getting in mainline.
Two users confirmed the patch works for them, though no one could be
bothered to post proper Tested-by here :(

https://lore.kernel.org/linux-usb/P1FsfbW--F-9@xxxxxxx/
https://lore.kernel.org/linux-usb/CY8PR14MB59803EC0F6C7FD39A6D3C42FA0BF2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/

> 
> > I kept val unchanged for the error log, restored the original handshake
> > formatting, and explicitly preserve OS Owned when forcing BIOS Owned
> > clear after a timeout. Documented timeout issue in commit message.
> > 
> > I repeated the same S3 test on the unmodified
> > 7.1.8-ogc1.1.fc44.x86_64 distribution kernel using the test module, with
> > the same successful result.
> > 
> > Changes in v5:
> > - Preserve the original ownership value for error logging.
> > - Restore the original handshake formatting.
> > - Explicitly retain OS Owned in the timeout fallback.
> > 
> >   drivers/usb/host/pci-quirks.c | 13 ++++++++-----
> >   1 file changed, 8 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
> > index 0404489c2f6a..2b12a35e6f10 100644
> > --- a/drivers/usb/host/pci-quirks.c
> > +++ b/drivers/usb/host/pci-quirks.c
> > @@ -1193,10 +1193,11 @@ static void quirk_usb_handoff_xhci(struct pci_dev *pdev)
> >   			 && pdev->device == 0x0014)) {
> >   		val = (val | XHCI_HC_OS_OWNED) & ~XHCI_HC_BIOS_OWNED;
> >   		writel(val, base + ext_cap_offset);
> > -	}
> > -
> > -	/* If the BIOS owns the HC, signal that the OS wants it, and wait */
> > -	if (val & XHCI_HC_BIOS_OWNED) {
> > +	} else {
> > +		/*
> > +		 * Perform the standard handoff and leave OS ownership set to
> > +		 * keep the BIOS at bay during subsequent suspends.
> > +		 */
> >   		writel(val | XHCI_HC_OS_OWNED, base + ext_cap_offset);
> >   
> >   		/* Wait for 1 second with 10 microsecond polling interval */
> > @@ -1208,7 +1209,9 @@ static void quirk_usb_handoff_xhci(struct pci_dev *pdev)
> >   			dev_warn(&pdev->dev,
> >   				 "xHCI BIOS handoff failed (BIOS bug ?) %08x\n",
> >   				 val);
> > -			writel(val & ~XHCI_HC_BIOS_OWNED, base + ext_cap_offset);
> > +			writel((val | XHCI_HC_OS_OWNED) &
> > +			       ~XHCI_HC_BIOS_OWNED,
> > +			       base + ext_cap_offset);
> >   		}
> >   	}
> >     
>