Re: [REGRESSION] [REPRO] USB-A devices not working on boot after recent USB merge

[Michal Pecio <michal.pecio@gmail.com>]

On Thu, 9 Oct 2025 00:25:55 +0200, Arisa Snowbell wrote:
> This is what I get when I use good kernel:
> 
> kernel: xhci_hcd 0000:7a:00.0: xHCI Host Controller
> kernel: xhci_hcd 0000:7a:00.0: new USB bus registered, assigned bus number 9
> kernel: xhci_hcd 0000:7a:00.0: USB3 root hub has no ports
> kernel: xhci_hcd 0000:7a:00.0: hcc params 0x0110ffc5 hci version 0x120
> quirks 0x0000000200000010
> kernel: xhci_hcd 0000:7a:00.0: xHCI Host Controller
> kernel: xhci_hcd 0000:7a:00.0: new USB bus registered, assigned bus number 10
> kernel: xhci_hcd 0000:7a:00.0: Host supports USB 3.0 SuperSpeed
> kernel: usb usb9: New USB device found, idVendor=1d6b, idProduct=0002,
> bcdDevice= 6.17
> kernel: usb usb9: New USB device strings: Mfr=3, Product=2, SerialNumber=1
> kernel: usb usb9: Product: xHCI Host Controller
> kernel: usb usb9: Manufacturer: Linux
> 6.17.0-1-mainline-12298-gf5bd2142c274 xhci-hcd
> kernel: usb usb9: SerialNumber: 0000:7a:00.0
> kernel: hub 9-0:1.0: USB hub found
> kernel: hub 9-0:1.0: 1 port detected
> kernel: usb usb10: We don't know the algorithms for LPM for this host,
> disabling LPM.
> kernel: usb usb10: New USB device found, idVendor=1d6b,
> idProduct=0003, bcdDevice= 6.17
> kernel: usb usb10: New USB device strings: Mfr=3, Product=2, SerialNumber=1
> kernel: usb usb10: Product: xHCI Host Controller
> kernel: usb usb10: Manufacturer: Linux
> 6.17.0-1-mainline-12298-gf5bd2142c274 xhci-hcd
> kernel: usb usb10: SerialNumber: 0000:7a:00.0
> kernel: hub 10-0:1.0: USB hub found
> kernel: hub 10-0:1.0: config failed, hub doesn't have any ports! (err -19)
> 
> where the 2.0 USB's work, mice is powered on, with the bad kernel the
> mice doesn't even power the LED's on.
> In the bad kernel its missing the New USB and all.

Okay, thanks. I now see what's going on.

I have successfully reproduced it on a normal controller by patching
the driver to simply ignore any USB3 ports. With this patch, no root
hubs are registered at all until I revert the "bad" commit.

In my case it's an idiotic little problem:

xhci_pci_common_probe()
{
	usb_hcd_pci_probe() {
		// allocate xhci
		xhci_run(xhci);
	}

	xhci->allow_single_roothub = 1;
}

The thing is that xhci_run() needs allow_single_roothub to already
be set when it executes, but we can't do it before xhci is allocated.
And some non-PCI drivers don't want it to be set.

Can you check if this patch fixes things for you?

It is obviously not a real solution, but it's good enough for xhci_pci
and sufficient to check if no other problems remain in your case.

---
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 485ea7fc0433..354443316bfb 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1735,8 +1735,7 @@ static inline bool xhci_hcd_is_usb3(struct usb_hcd *hcd)
 
 static inline bool xhci_has_one_roothub(struct xhci_hcd *xhci)
 {
-	return xhci->allow_single_roothub &&
-	       (!xhci->usb2_rhub.num_ports || !xhci->usb3_rhub.num_ports);
+	return (!xhci->usb2_rhub.num_ports || !xhci->usb3_rhub.num_ports);
 }
 
 #define xhci_dbg(xhci, fmt, args...) \