Re: [RFC][PATCH 3/3] usb: dwc3: Registering a role switch in the DRD code.

From: John Stultz <john.stultz@linaro.org>
To: Roger Quadros <rogerq@ti.com>
Cc: lkml <linux-kernel@vger.kernel.org>,
	Yu Chen <chenyu56@huawei.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Chunfeng Yun <chunfeng.yun@mediatek.com>,
	Felipe Balbi <balbi@kernel.org>,
	Hans de Goede <hdegoede@redhat.com>,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	Jun Li <lijun.kernel@gmail.com>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Linux USB List <linux-usb@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>
Subject: Re: [RFC][PATCH 3/3] usb: dwc3: Registering a role switch in the DRD code.
Date: Tue, 15 Oct 2019 12:10:22 -0700	[thread overview]
Message-ID: <CALAqxLUVd5Eo_9tuP9aQUpNT0gnewBv8Dpvsj8UT3MucmzCJVQ@mail.gmail.com> (raw)
In-Reply-To: <9e86bb7b-5dd2-760e-c324-fe1c1ee41868@ti.com>

On Tue, Oct 15, 2019 at 1:25 AM Roger Quadros <rogerq@ti.com> wrote:
> On 03/10/2019 02:16, John Stultz wrote:
> > @@ -487,7 +539,28 @@ int dwc3_drd_init(struct dwc3 *dwc)
> >       if (IS_ERR(dwc->edev))
> >               return PTR_ERR(dwc->edev);
> >
> > -     if (dwc->edev) {
> > +     if (device_property_read_bool(dwc->dev, "usb-role-switch")) {
>
> I think we should use role switch unconditionally and get rid of the
> debugfs role status/change mechanism.
>
> > +             struct usb_role_switch_desc dwc3_role_switch = {0};
> > +             u32 mode;
> > +
> > +             if (device_property_read_bool(dwc->dev,
> > +                                           "role-switch-default-host")) {
> > +                     dwc->role_switch_default_mode = USB_DR_MODE_HOST;
> > +                     mode = DWC3_GCTL_PRTCAP_HOST;
> > +             } else {
> > +                     dwc->role_switch_default_mode = USB_DR_MODE_PERIPHERAL;
> > +                     mode = DWC3_GCTL_PRTCAP_DEVICE;
> > +             }
> > +             dwc3_role_switch.fwnode = dev_fwnode(dwc->dev);
> > +             dwc3_role_switch.set = dwc3_usb_role_switch_set;
> > +             dwc3_role_switch.get = dwc3_usb_role_switch_get;
> > +             dwc->role_sw = usb_role_switch_register(dwc->dev,
> > +                                                     &dwc3_role_switch);
> > +             if (IS_ERR(dwc->role_sw))
> > +                     return PTR_ERR(dwc->role_sw);
> > +
> > +             dwc3_set_mode(dwc, mode);
> > +     } else if (dwc->edev) {
>
> Role switch should exist regardless if dwc->edev is present or not.

Does that risk duplicative mode sets when things change (via the
dwc3_drd_notifier and dwc3_usb_role_switch_set calls?).

thanks
-john