Re: [PATCH v1 1/3] gpio: defer probe if pinctrl cannot be found

[Stephen Warren]

On 07/10/2015 10:21 AM, Tomeu Vizoso wrote:
> On 10 July 2015 at 17:27, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote:
> > On 07/10/2015 03:29 AM, Tomeu Vizoso wrote:
> > > On 1 July 2015 at 19:36, Rob Herring <robherring2@xxxxxxxxx> wrote:
> > > > On Wed, Jul 1, 2015 at 7:45 AM, Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
> > > > wrote:
> > > > > When an OF node has a pin range for its GPIOs, return -EPROBE_DEFER if
> > > > > the pin controller isn't available.
> > > > >
> > > > > Otherwise, the GPIO range wouldn't be set at all unless the pin
> > > > > controller probed always before the GPIO chip.
> > > > >
> > > > > With this change, the probe of the GPIO chip will be deferred and will
> > > > > be retried at a later point, hopefully once the pin controller has been
> > > > > registered and probed already.
> > > >
> > > >
> > > > This will break cases where the pinctrl driver does not exist, but the
> > > > DT contains pinctrl bindings. We can have similar problems already
> > > > with clocks though. However, IMO this problem is a bit different in
> > > > that pinctrl is more likely entirely optional while clocks are often
> > > > required. You may do all pin setup in bootloader/firmware on some
> > > > boards and not others. Of course then why put pinctrl in the DT in
> > > > that case? They could be present just due to how chip vs. board dts
> > > > files are structured.
> > >
> > >
> > > I see. My instinct tells me that it would be better if the gpio-ranges
> > > property was set in the board dts, but I don't really know what each
> > > mach does with its DTSs.
> >
> >
> > That doesn't make sense; the mapping between GPIO controller pins and pin
> > controller pins is a property of the SoC not the board.
>
>  From what Rob said above, apparently some boards will rely on the pin
> setup done by the bootloader, and some other boards with the same soc
> will want to do it in the kernel. So it's not really a difference in
> the hw itself, but what expectations exist about the firmware on a
> specific board.

Sure, but none of that changes the mapping between the GPIO and pin 
controller pins.

--
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/