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

[Roger Quadros]

On 15/10/2019 22:10, John Stultz wrote:
> On Tue, Oct 15, 2019 at 1:25 AM Roger Quadros <rogerq@xxxxxx> 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?).

Yes, we need to deal with it in the driver. e.g. in current case
when debugfs overrides a role from "otg" to "host" or "device",
we ignore the notifier.

Something similar could be done with role switch I think.

Felipe, what do you think?

--
cheers,
-roger
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