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

[Mario Limonciello <superm1@kernel.org>]

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@vger.kernel.org
> Assisted-by: LLM
> Signed-off-by: Rishabh Jain <rishabh.jain1198@gmail.com>
> ---

Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>

> 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);
>   		}
>   	}
>