Re: [PATCH v2 RFT] usb: xhci-pci: Fix USB2-only root hub registration

[Hanabishi <i.r.e.c.c.a.k.u.n+kernel.org@gmail.com>]

On 10/13/25 08:04, Michal Pecio wrote:
> A recent change to hide USB3 root hubs of USB2-only controllers broke
> registration of USB2 root hubs - allow_single_roothub is set too late,
> and by this time xhci_run() has already deferred root hub registration
> until after the shared HCD is added, which will never happen.
> 
> This makes such controllers unusable, but testers didn't notice since
> they were only bothered by warnings about empty USB3 root hubs. The bug
> causes problems to other people who actually use such HCs and I was
> able to confirm it on an ordinary HC by patching to ignore USB3 ports.
> 
> Setting allow_single_roothub during early setup fixes things.
> 
> Reported-by: Arisa Snowbell <arisa.snowbell@gmail.com>
> Closes: https://lore.kernel.org/linux-usb/CABpa4MA9unucCoKtSdzJyOLjHNVy+Cwgz5AnAxPkKw6vuox1Nw@mail.gmail.com/
> Reported-by: Michal Kubecek <mkubecek@suse.cz>
> Closes: https://lore.kernel.org/linux-usb/lnb5bum7dnzkn3fc7gq6hwigslebo7o4ccflcvsc3lvdgnu7el@fvqpobbdoapl/
> Fixes: 719de070f764 ("usb: xhci-pci: add support for hosts with zero USB3 ports")
> Suggested-by: Mathias Nyman <mathias.nyman@linux.intel.com>
> Signed-off-by: Michal Pecio <michal.pecio@gmail.com>
> ---
> 
> New in v2:
> - don't set allow_single_roothub twice, it's harmless but lame
> - credit and Cc another reporter
> 
>   drivers/usb/host/xhci-pci.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
> index 13454bef14d3..d292adc65e5a 100644
> --- a/drivers/usb/host/xhci-pci.c
> +++ b/drivers/usb/host/xhci-pci.c
> @@ -588,6 +588,8 @@ static int xhci_pci_setup(struct usb_hcd *hcd)
>   	if (!usb_hcd_is_primary_hcd(hcd))
>   		return 0;
>   
> +	xhci->allow_single_roothub = 1;
> +
>   	if (xhci->quirks & XHCI_PME_STUCK_QUIRK)
>   		xhci_pme_acpi_rtd3_enable(pdev);
>   
> @@ -643,7 +645,6 @@ int xhci_pci_common_probe(struct pci_dev *dev, const struct pci_device_id *id)
>   	xhci = hcd_to_xhci(hcd);
>   	xhci->reset = reset;
>   
> -	xhci->allow_single_roothub = 1;
>   	if (!xhci_has_one_roothub(xhci)) {
>   		xhci->shared_hcd = usb_create_shared_hcd(&xhci_pci_hc_driver, &dev->dev,
>   							 pci_name(dev), hcd);

Hello. I just want to confirm that the patch works for me too.

Hadrware setup:

0d:00.0 USB controller [0c03]: Advanced Micro Devices, Inc. [AMD] Raphael/Granite Ridge USB 2.0 xHCI [1022:15b8]

6.18-rc1:

[    2.170519] xhci_hcd 0000:0d:00.0: xHCI Host Controller
[    2.170520] xhci_hcd 0000:0d:00.0: new USB bus registered, assigned bus number 7
[    2.171768] xhci_hcd 0000:0d:00.0: USB3 root hub has no ports
[    2.171783] xhci_hcd 0000:0d:00.0: hcc params 0x0110ffc5 hci version 0x120 quirks 0x0000000200000010
(usb port is not populated and does not work)

6.18-rc1 with the patch applied:

[    2.162897] xhci_hcd 0000:0d:00.0: xHCI Host Controller
[    2.162904] xhci_hcd 0000:0d:00.0: new USB bus registered, assigned bus number 7
[    2.164156] xhci_hcd 0000:0d:00.0: USB3 root hub has no ports
[    2.164171] xhci_hcd 0000:0d:00.0: hcc params 0x0110ffc5 hci version 0x120 quirks 0x0000000200000010
[    2.164356] usb usb7: New USB device found, idVendor=1d6b, idProduct=0002, bcdDevice= 6.18
[    2.164357] usb usb7: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[    2.164358] usb usb7: Product: xHCI Host Controller
[    2.164358] usb usb7: Manufacturer: Linux 6.18.0-rc1 xhci-hcd
[    2.164359] usb usb7: SerialNumber: 0000:0d:00.0
[    2.164390] hub 7-0:1.0: USB hub found
[    2.164397] hub 7-0:1.0: 1 port detected
(usb port is populated and does work)