Re: [PATCH] pinctrl: at91: fix deferred probing support

[Rob Herring <robh@kernel.org>]

On Fri, Jul 13, 2018 at 3:47 AM Alexandre Belloni
<alexandre.belloni@bootlin.com> wrote:
>
> Hi Rob,
>
> On 12/07/2018 13:22:22-0600, Rob Herring wrote:
> > AT91 pinctrl deferred probing support is broken if the GPIO devices
> > haven't probed first and set gpio_banks to non-zero. The later condition
> > that only some GPIO devices haven't probed can't actually happen as
> > either all the GPIO devices have probed first or none of them have. Plus
> > the pinctrl driver has already returned -EINVAL, so it's not on the
> > deferred list to retry probing.
> >
> > Fix this by consolidating the checking that all GPIO devices are probed.
> >
> > Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
> > Cc: Linus Walleij <linus.walleij@linaro.org>
> > Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
> > Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
> > Cc: linux-arm-kernel@lists.infradead.org
> > Cc: linux-gpio@vger.kernel.org
> > Signed-off-by: Rob Herring <robh@kernel.org>
> > ---
> > This is a result of trying to remove of_platform_default_populate from
> > at91 code and relying on the DT core handling populating devices. That
> > changed the probe order and broke booting.
> >
>
> This solves part of the issue but when tested with the
> of_platform_default_populate removal, many drivers will fail with
> gpiod_set_value: invalid GPIO (errorpointer)
>
> or
>
> gpiod_get_value: invalid GPIO (errorpointer)
>
> This happens both before and after the pinctrl driver probed.
>
> I didn't investigate much yet.

Looks to me like it may be a circular dependency. The GPIO request
functions depend on the pinctrl driver which depends on the gpio
driver. Maybe returning EPROBE_DEFER in at91_gpio_request_enable and
removing the requirement that the GPIO driver probe first would fix
it...

Rob