linux-kernel - Re: [PATCH 1/1] usb: dwc3: Do not get extcon device when usb-role-switch is used

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Date:   Tue, 8 Nov 2022 16:43:42 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc:     Janne Grunau <j@...nau.net>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        Sven Peter <sven@...npeter.de>,
        "stable@...nel.org" <stable@...nel.org>,
        Andrey Smirnov <andrew.smirnov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] usb: dwc3: Do not get extcon device when
 usb-role-switch is used

On Tue, Nov 08, 2022 at 02:02:19AM +0000, Thinh Nguyen wrote:
> Hi,
> 
> On Sun, Nov 06, 2022, Janne Grunau wrote:
> > The change breaks device tree based platforms with PHY device and use
> > usb-role-switch instead of an extcon switch. extcon_find_edev_by_node()
> > will return EPROBE_DEFER if it can not find a device so probing without
> > an extcon device will be deferred indefinitely. Fix this by
> > explicitly checking for usb-role-switch.
> > At least the out-of-tree USB3 support on Apple silicon based platforms
> > using dwc3 with tipd USB Type-C and PD controller is affected by this
> > issue.
> > 
> > Fixes: d182c2e1bc92 ("usb: dwc3: Don't switch OTG -> peripheral if extcon is present")
> > Cc: stable@...nel.org
> > Signed-off-by: Janne Grunau <j@...nau.net>
> > ---
> >  drivers/usb/dwc3/core.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > index c0e7c76dc5c8..1f348bc867c2 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -1710,6 +1710,16 @@ static struct extcon_dev *dwc3_get_extcon(struct dwc3 *dwc)
> >  	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0)
> >  		return extcon_get_extcon_dev(name);
> >  
> > +	/*
> > +	 * Check explicitly if "usb-role-switch" is used since
> > +	 * extcon_find_edev_by_node() can not be used to check the absence of
> 
> can not -> can't or cannot

"can not" is fine.

> 
> > +	 * an extcon device. In the absence of an device it will always return
> 
> "a" device,

Not an issue.

> > +	 * EPROBE_DEFER.
> > +	 */
> > +	if (IS_ENABLED(CONFIG_USB_ROLE_SWITCH) &&
> > +	    device_property_read_bool(dev, "usb-role-switch"))
> > +		return NULL;
> > +
> >  	/*
> >  	 * Try to get an extcon device from the USB PHY controller's "port"
> >  	 * node. Check if it has the "port" node first, to avoid printing the
> > -- 
> > 2.37.3
> > 
> 
> Looks like the "port" node check from c824c73a5e08 ("usb: dwc3: drd:
> Avoid error when extcon is missing") did not account for this platform
> setup.
> 
> This looks fine to me. Should we cleanup the incomplete check and stale
> comment right after this too (as a separate patch)?

Is this a Reviewed-by: ?

thanks,

greg k-h