Re: [PATCH v4 2/2] gpio: mxc: Always set GPIOs used as interrupt source to INPUT mode

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Mon, Jul 25, 2022 at 12:50 AM Marek Vasut <marex@xxxxxxx> wrote:

> Always configure GPIO pins which are used as interrupt source as INPUTs.
> In case the default pin configuration is OUTPUT, or the prior stage does
> configure the pins as OUTPUT, then Linux will not reconfigure the pin as
> INPUT and no interrupts are received.
>
> Always configure interrupt source GPIO pin as input to fix the above case.
>
> Fixes: 07bd1a6cc7cbb ("MXC arch: Add gpio support for the whole platform")
> Signed-off-by: Marek Vasut <marex@xxxxxxx>
> Cc: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Cc: Loic Poulain <loic.poulain@xxxxxxxxxx>
> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> Cc: NXP Linux Team <linux-imx@xxxxxxx>
> Cc: Peng Fan <peng.fan@xxxxxxx>
> Cc: Shawn Guo <shawnguo@xxxxxxxxxx>
> ---
> V2: Actually update and clear bits in GDIR register
> V3: Rebase on top of new patch 1/2, expand CC list, add Fixes tag
> V4: No change

I understand what you are trying to achieve, and it makes sense.

There's is just this one generic GPIO-based driver that makes me
a little bit nervous here.

Consider:
drivers/media/cec/platform/cec-gpio/cec-gpio.c
Look what the driver is doing with the gpiod_* operations on it's
cec->cec_gpio.

A certain GPIO pin is switched back and forth between input and
output and in input mode, it is used to generate interrupts as well.

Will this still work fine with the MXC driver after this change?
At least it will be set to input mode twice, but I suppose that is
fine, it's not your fault that the frameworks are orthogonal.

Yours,
Linus Walleij