[PATCH] usb: core: improve handling of hubs with no ports

[Alan Stern]

On Tue, Feb 22, 2022 at 10:13:09PM +0100, Heiner Kallweit wrote:
> I get the "hub doesn't have any ports" error message on a system with
> Amlogic S905W SoC. Seems the SoC has internal USB 3.0 supports but
> is crippled with regard to USB 3.0 ports.
> Maybe we shouldn't consider this scenario an error. So let's change
> the message to info level, but otherwise keep the handling of the
> scenario as it is today. With the patch it looks like this on my
> system.
> 
> dwc2 c9100000.usb: supply vusb_d not found, using dummy regulator
> dwc2 c9100000.usb: supply vusb_a not found, using dummy regulator
> dwc2 c9100000.usb: EPs: 7, dedicated fifos, 712 entries in SPRAM
> xhci-hcd xhci-hcd.0.auto: xHCI Host Controller
> xhci-hcd xhci-hcd.0.auto: new USB bus registered, assigned bus number 1
> xhci-hcd xhci-hcd.0.auto: hcc params 0x0228f664 hci version 0x100 quirks 0x0000000002010010
> xhci-hcd xhci-hcd.0.auto: irq 49, io mem 0xc9000000
> hub 1-0:1.0: USB hub found
> hub 1-0:1.0: 2 ports detected
> xhci-hcd xhci-hcd.0.auto: xHCI Host Controller
> xhci-hcd xhci-hcd.0.auto: new USB bus registered, assigned bus number 2
> xhci-hcd xhci-hcd.0.auto: Host supports USB 3.0 SuperSpeed
> usb usb2: We don't know the algorithms for LPM for this host, disabling LPM.
> hub 2-0:1.0: USB hub found
> hub 2-0:1.0: hub has no ports, exiting
> 
> Signed-off-by: Heiner Kallweit <hkallweit1 at gmail.com>
> ---
>  drivers/usb/core/hub.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 83b5aff25..e3f40d1f4 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -1423,9 +1423,8 @@ static int hub_configure(struct usb_hub *hub,
>  		ret = -ENODEV;
>  		goto fail;
>  	} else if (hub->descriptor->bNbrPorts == 0) {
> -		message = "hub doesn't have any ports!";
> -		ret = -ENODEV;
> -		goto fail;
> +		dev_info(hub_dev, "hub has no ports, exiting\n");
> +		return -ENODEV;
>  	}
>  
>  	/*

How about instead changing xhci-hcd so that it doesn't try to register 
a USB-3 root hub if the controller doesn't have any USB-3 ports?  I 
think that would make more sense.

Alan Stern