Re: [RFC PATCH 9/9] usb: dwc2: Add gadget driver

[Sascha Hauer <s.hauer@pengutronix.de>]

On Mon, Jan 27, 2020 at 06:18:04PM +0100, Jules Maselbas wrote:
> Hi Sascha,
> 
> On Mon, Jan 27, 2020 at 02:40:34PM +0100, Sascha Hauer wrote:
> > Hi Jules,
> > > +int dwc2_gadget_init(struct dwc2 *dwc2)
> > > +{
> > > +	u32 dctl;
> > > +	int epnum;
> > > +	int ret;
> > > +
> > > +	dwc2_core_init(dwc2);
> > 
> > This is called once during probe here and once during host init, it
> > should probably only be called once.
> Yes this is called in both gadget and host init, the only difference is
> that in host mode the mode is forced before. I still need see if the
> force mode has to be set before the core_init.
> 
> The force mode is also kinda of a hack and I want to find a better way
> of handling the case where the controller is otg but the connector is
> not otg but host only.
> 
> For now I think it is okay to do the core_init in each mode, since otg mode is
> not supported, you should either use the `usb` or the `usbgadget` command.
> 
> > 
> > I would expect both host and gadget support to be optional, but instead
> > both is unconditionally compiled in. Does this link when USB host or gadget
> > support is disabled?
> Good point, I forgot to do this. I've made the change locally this will be
> included in the next version.
> 
> > How does the driver select between host and gadget mode? Normally we do
> > not have any real OTG support in barebox. With dr_mode = "otg" in the
> > device tree we usually register some device which the user can use to
> > specify the mode during runtime. How is this solved here?
> The selection is done with `usb` and `usbgadget` commands. The first will
> call host_init which will "select" the host mode (by forcing the controller
> mode to host). The later command will setup the controller in peripheral mode.

For the sake of consistency with other the drivers Could you call
usb_register_otg_device() instead? It requires one additional step for
the user, but it allows you for example to use other host controllers
and the otg controller in gadget mode afterwards.

Sascha

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