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

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

[McKenna Fan]

This is an independent test report for [PATCH v5] usb: pci-quirks: always assert xHCI OS ownership.


I independently reproduced the problem and tested the proposed ownership behavior on a different AMD Promontory xHCI controller.

My affected controller is:

AMD B550 / Promontory-19 xHCIPCI 1022:43ee0000:02:00.0

The machine runs Manjaro and uses ACPI deep/S3 suspend.


I ended up collecting what is, frankly, an absurd amount of evidence while chasing this, including firmware analysis and repeated A/B testing, but the shortest useful version is:


Stock Manjaro 7.2.4 kernel, no helper module loaded:

EXTCAP_USBLEGSUP = 0x00000801EXTCAP_USBLEGCTLSTS = 0x40000000HC BIOS Owned = 0
HC OS Owned = 0




After entering deep S3:

xhci_hcd 0000:02:00.0: xHC error in resume, USBSTS 0x401, Reinit

After the failed resume:

EXTCAP_USBLEGSUP = 0x00000801EXTCAP_USBLEGCTLSTS = 0xc0000000

So HC OS Owned remained clear.


I then booted a custom build of the same Manjaro 7.2.4 kernel implementing the proposed behavior of asserting HC OS Owned in the xHCI handoff path. No ownership helper module was loaded.


Before S3:

EXTCAP_USBLEGSUP = 0x01000801EXTCAP_USBLEGCTLSTS = 0x40000000

HC BIOS Owned = 0

HC OS Owned = 1




I performed five consecutive deep-S3 suspend/resume cycles, including one approximately four-minute S3 residency.


All five resumed without:

xHC error in resumeUSBSTS 0x401Reinit

After the final resume:

EXTCAP_USBLEGSUP = 0x01000801EXTCAP_USBLEGCTLSTS = 0xc0000000

HC OS Owned remained asserted.


I then immediately rebooted back into the otherwise matching unmodified Manjaro 7.2.4 kernel. With no helper loaded, USBLEGSUP returned to 0x00000801, and the very first deep-S3 cycle reproduced:

xhci_hcd 0000:02:00.0: xHC error in resume, USBSTS 0x401, Reinit

This also agrees with earlier reversible testing using a very small test module which changed only HC OS Owned in USBLEGSUP:

0x00000801 -> 0x01000801

It did not reset or unbind the controller, clear USBLEGCTLSTS, or make other xHCI MMIO changes. With OS Owned asserted, repeated S3 resumes succeeded; clearing OS Owned again caused the resume failure to return.


So on this 1022:43ee controller I can independently reproduce the same causal relationship:

OS Owned clear    -> USBSTS 0x401 / controller reinitOS Owned asserted -> clean S3 resumeOS Owned clear    -> failure returnskernel asserts it -> 5/5 clean resumesstock kernel      -> first S3 fails again

One potentially useful detail is that USBLEGCTLSTS changed from 0x40000000 to 0xc0000000 after resume in both the successful and failed cases. That status change therefore does not distinguish the two outcomes here; HC OS Owned does.


This appears to extend the observed problem beyond the 1022:43fc controller in the original report to at least the related 1022:43ee Promontory controller.


I have complete logs from the positive and negative-control boots and can provide the longer A/B history or firmware findings if useful.


AI assistance disclosure: ChatGPT 5.6 Sol and Astra-medium were used during the investigation for source/code analysis, experimental planning, log comparison, and assistance preparing this report. All commands, kernel builds, suspend/resume experiments, register reads, and reported results were executed and verified on the physical system by me.


P.S. If Rishabh happens to enjoy following journalctl warnings farther than is probably reasonable, I have another USB rabbit hole which may be of interest: a kernel.org Bugzilla report on a USB3 Type-C peer-collision / port-power-management warning. The useful part is comment #1, where the issue gets reframed after more investigation:


https://bugzilla.kernel.org/show_bug.cgi?id=221987#c1


Different bug, but another fairly innocent-looking USB warning that turned out to have considerably more behind it than expected.

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

[Rishabh Jain]

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>
---
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);
 		}
 	}
 
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