Re: [RFC/PATCH] extcon: otg_gpio: add driver for USB OTG port controlled by GPIO(s)

[Sergei Shtylyov]

Hello.

On 12/23/2014 10:57 PM, David Cohen wrote:

> > > Some platforms have an USB OTG port fully (or partially) controlled by
> > > GPIOs:

> > > (1) USB ID is connected directly to GPIO

> > > Optionally:
> > > (2) VBUS is enabled by a GPIO (when ID is grounded)

> >     Can't the host driver still control Vbus?

> I can't a clean way for host driver to control VBUS considering it
> depends on USB ID.

   You're using the cable state notifiers, why not control Vbus from there?
You need some way of passing the GPIO to host driver though... I assume you're 
not using the device tree, and your host controllers live on PCI, so the 
platform data is out of question. You may be right then...

> > > (3) Platform has 2 USB controllers connected to same port: one for
> > >      device and one for host role. D+/- are switched between phys
> > >      by GPIO.

> > > As per initial version, this driver has the duty to control whether
> > > USB-Host cable is plugged in or not:
> > >   - If yes, OTG port is configured for host role
> > >   - If no, by standard, the OTG port is configured for device role

> > > Signed-off-by: David Cohen <david.a.cohen@xxxxxxxxxxxxxxx>
> > > ---

> > > Hi,

> > > Some Intel Bay Trail boards have an unusual way to handle the USB OTG port:
> > >   - The USB ID pin is connected directly to GPIO on SoC
> > >   - When in host role, VBUS is provided by enabling a GPIO
> > >   - Device and host roles are supported by 2 independent controllers with D+/-
> > >     pins from port switched between different phys according a GPIO level.

> > > The ACPI table describes this USB port as a (virtual) device with all the
> > > necessary GPIOs. This driver implements support to this virtual device as an
> > > extcon class driver. All drivers that depend on the USB OTG port state (USB phy,
> > > PMIC, charge detection) will listen to extcon events.

> >     It's very close to my setup on R-Car R8A7791 based boards. :-)
> > I have already submitted Maxim MAX3355 OTG chip GPIO-based driver.

> Hm. I'll look for it. Thanks for pointing.

   http://marc.info/?l=linux-usb&m=141825413802370
   In my case, Vbus is not controlled via GPIO though. I would have probably 
used the generic GPIO extcon driver if I didn't have to drive MAX3355's SHDN# 
pin high...
   There were also some other patches for this issue, the one probably 
interesting to you is there:

   http://marc.info/?l=linux-usb&m=141877180912359

> > > Comments are welcome.

> > > Br, David

[...]

> > > +static int __init vuport_init(void)
> > > +{
> > > +	return platform_driver_register(&vuport_driver);
> > > +}
> > > +subsys_initcall(vuport_init);

> >     Hm, why?

> We have drivers that depend on this one during their probe.

   What about deferred probing? With EPROBE_DEFER we don't need to play the 
initcall games any more AFAIU.

> Br, David

WBR, Sergei

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/