RE: [PATCH v2] usb: host: xhci-rcar: Avoid long wait in xhci_reset()

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Hi,

> From: Felipe Balbi
> Sent: Friday, April 22, 2016 6:37 PM
> 
> Hi,
> 
> Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx> writes:
> > The firmware of R-Car USB 3.0 host controller will control the reset.
> > So, if the xhci driver doesn't do firmware downloading (e.g. kernel
> > configuration is CONFIG_USB_XHCI_PLATFORM=y and CONFIG_USB_XHCI_RCAR
> > is not set), the reset of USB 3.0 host controller doesn't work
> > correctly. Then, the host controller will cause long wait in
> > xhci_reset() because the CMD_RESET bit of op_regs->command is not
> > cleared for 10 seconds.
> >
> > So, this patch modifies the xhci_rcar_init_quirk() in xhci-rcar.h
> > to exit the probe function immediately.
> >
> > Fixes: 4ac8918f3a7 (usb: host: xhci-plat: add support for the R-Car H2 and M2 xHCI controllers)
> > Cc: <stable@xxxxxxxxxxxxxxx> # v3.17+
> > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> > ---
> >  Changes from v1:
> >   - Revise the commit log.
> >     (http://www.spinics.net/lists/stable/msg130007.html)
> >
> >  drivers/usb/host/xhci-rcar.h | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/host/xhci-rcar.h b/drivers/usb/host/xhci-rcar.h
> > index 2941a25..2afed68 100644
> > --- a/drivers/usb/host/xhci-rcar.h
> > +++ b/drivers/usb/host/xhci-rcar.h
> > @@ -24,7 +24,11 @@ static inline void xhci_rcar_start(struct usb_hcd *hcd)
> >
> >  static inline int xhci_rcar_init_quirk(struct usb_hcd *hcd)
> >  {
> > -	return 0;
> > +	/*
> > +	 * To avoid wait and timeout in xhci_reset() if CONFIG_XHCI_RCAR is
> > +	 * disabled, this function fails.
> > +	 */
> > +	return -ENODEV;
> 
> okay, if I understood correctly the thing is that you have a kernel
> built with XHCI platform support but without XHCI RCAR support. Then, if
> you run this kernel on RCAR board, you see this CMD_RESET problem,
> right?

Yes, that's right.

> Isn't this pointing to the fact that xhci-plat.ko built without RCAR
> isn't exactly compatible with RCAR ?

You're correct.

> IOW:
> 
> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> index 676ea458148b..3e39320564ce 100644
> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c
> @@ -112,6 +112,7 @@ static const struct of_device_id usb_xhci_of_match[] = {
>  	}, {
>  		.compatible = "marvell,armada-380-xhci",
>  		.data = &xhci_plat_marvell_armada,
> +#if IS_ENABLED(CONFIG_USB_XHCI_RCAR)
>  	}, {
>  		.compatible = "renesas,xhci-r8a7790",
>  		.data = &xhci_plat_renesas_rcar_gen2,
> @@ -130,6 +131,7 @@ static const struct of_device_id usb_xhci_of_match[] = {
>  	}, {
>  		.compatible = "renesas,rcar-gen3-xhci",
>  		.data = &xhci_plat_renesas_rcar_gen3,
> +#endif
>  	},
>  	{},
>  };

I see. This can avoid probing the xhci-plat.ko if RCAR is disabled.

Best regards,
Yoshihiro Shimoda

> Rob, should we limit compatible flags like this ? Without
> CONFIG_USB_XHCI_RCAR, this driver won't work on RCAR but, as you can
> see, this driver might still work on other non-RCAR platforms.
> 
> What's your take on this ?
> 
> --
> balbi
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