Re: [PATCH 6/6] ARM: shmobile: Armadillo800EVA: Reference DT implementation

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Bastian,

On Friday 05 April 2013 13:28:07 Bastian Hecht wrote:
> 2013/4/5 Laurent Pinchart <laurent.pinchart@ideasonboard.com>:
> > Hi Bastian,
> > 
> > On Thursday 04 April 2013 17:58:40 Bastian Hecht wrote:
> >> 2013/4/4 Laurent Pinchart <laurent.pinchart@ideasonboard.com>:
> >> > Hi Bastian,
> >> > 
> >> > Thanks for the patch.
> >> 
> >> [snip]
> >> 
> >> >> +     /* Touchscreen */
> >> >> +     gpio_request(GPIO_FN_IRQ10,     NULL); /* TP_INT */
> >> > 
> >> > Please, no function GPIO in reference DT implementations.
> >> 
> >> As far as I understood the pinctrl framework, we choose preconfigured
> >> settings (in pfc-r8a7740.c) for each device we want to run. We identify
> >> these devices by their names, like sh-sci.1. How does that work with
> >> devices connected to busses like the I2C controller for which we can't
> >> know which GPIOs we need in advance as it is board dependent?
> > 
> > pfc-r8a7740.c defines pin groups and functions. It's then up to board and
> > DT files to map the groups and functions they need to devices. The
> > mappings can be selected explicitly by drivers, or, for default mappings,
> > automatically by the device core. Please see the eva_pinctrl_map array in
> > arch/arm/mach-shmobile/board-armadillo800eva.c for mapping examples.
> 
> Thanks for the explanation.
> 
> >> >> +     gpio_request_one(166, GPIOF_OUT_INIT_HIGH, NULL); /* TP_RST_B */
> >> > 
> >> > The GPIO should be passed to the touchscreen driver through DT. As we
> >> > have no GPIO DT bindings for the r8a7740 yet, an option would be to
> >> > pass it through platform data (using OF_DEV_AUXDATA).
> >> 
> >> I don't see who would use that data. Does your suggestion include to
> >> expand the st1232 driver?
> > 
> > There's two options here. The one I was suggesting indeed involved
> > modifying the st1232 driver to handle the reset signal explicitly. The
> > other option would be to use pinctrl mappings to configure the GPIO. This
> > isn't possible yet with the PFC driver but I'm working on it.
> 
> Ah now I'm on track, I guess. So the idea is to be self-contained the st1232
> needs to be supplied with 2 GPIOs and while the IRQ GPIO is given
> (indirectly) by the IRQ number, the reset signal is missing. The
> "gpio_request(GPIO_FN_IRQ10,     NULL)" is purely board specific to route
> the IRQ signal correctly

That's correct. Such muxing should be performed using a default pinmux entry 
for the st1232 that you will need to add to the pinctrl maps table. The IRQ 
number is already passed to the st1232 through I2C board info, so no change is 
needed there.

> while the reset signal is already muxed correctly by default and just the
> output value is changed.

That's correct as well. The reset GPIO number should be passed to the st1232 
through platform data/DT, and the st1232 driver should request the GPIO and 
control the reset signal as needed.

> So I'll have a look at the driver and see if I can add the reset GPIO code.

Great, thank you.

-- 
Regards,

Laurent Pinchart