Re: [RFC][PATCH 2/3] usb: roles: Add usb role switch notifier.

[Hans de Goede]

Hi,

On 10/15/19 7:39 AM, John Stultz wrote:
> On Thu, Oct 3, 2019 at 1:51 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> > On 03-10-2019 22:37, John Stultz wrote:
> > > Fair point. I'm sort of taking a larger patchset and trying to break
> > > it up into more easily reviewable chunks, but I guess here I mis-cut.
> > >
> > > The user is the hikey960 gpio hub driver here:
> > >     https://git.linaro.org/people/john.stultz/android-dev.git/commit/?id=b06158a2d3eb00c914f12c76c93695e92d9af00f
> >
> > Hmm, that seems to tie the TypeC data-role to the power-role, which
> > is not going to work with role swapping.
>
> Thanks again for the feedback here. Sorry for the slow response. Been
> reworking some of the easier changes but am starting to look at how to
> address your feedback here.
>
> > What is controlling the usb-role-switch, and thus ultimately
> > causing the notifier you are suggesting to get called ?
>
> The tcpm_mux_set() call via tcpm_state_machine_work()
>
> > Things like TYPEC_VBUS_POWER_OFF and TYPEC_VBUS_POWER_ON
> > really beg to be modeled as a regulator and then the
> > Type-C controller (using e.g. the drivers/usb/typec/tcpm/tcpm.c
> > framework) can use that regulator to control things.
> > in case of the tcpm.c framework it can then use that
> > regulator to implement the set_vbus callback.
>
> So I'm looking at the bindings and I'm not sure exactly how to tie a
> regulator style driver into the tcpm for this?
> Looking at the driver I just see this commented out bit:
>     https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/usb/typec/tcpm/tcpm.c#n3075
>
> Do you happen to have a pointer to something closer to what you are describing?

Look at the tcpm_set_vbus implementation in drivers/usb/typec/tcpm/fusb302.c
you need to do something similar in your Type-C controller driver and
export the GPIO as as a gpio-controlled regulator and tie the regulator to
the connector.

Regards,

Hans