[PATCH] pinctrl: mediatek: paris: Directly modify registers to set GPIO direction

[Linus Walleij]

On Mon, Apr 27, 2026 at 4:10 AM Chen-Yu Tsai <wenst at chromium.org> wrote:

> pinctrl_gpio_direction_input() / pinctrl_gpio_direction_output() take
> the pinctrl mutex. This causes a gpiochip operations to need to sleep.
> Worse yet, the .can_sleep field in the gpiochip is not set. This causes
> the shared GPIO proxy to trip over, as it uses gpiod_cansleep() to check
> whether it can use a spinlock or needs a mutex. In this case, it ends
> up taking a spinlock, then calls pinctrl_gpio_direction_output(), which
> takes a mutex. This causes a huge warning.
>
> While this class of Mediatek hardware does not have separate clear/set
> registers, the pinctrl context has a spinlock that is taken whenever
> a register read-modify-write is done.
>
> Switch to directly setting the GPIO direction register bits to avoid
> the mutex.
>
> Signed-off-by: Chen-Yu Tsai <wenst at chromium.org>

You are essentially decoupling the pin control back-end from
the GPIO front-end, can you try to do this a more friendly way
that doesn't wrangle registers out of the pin controller like this?

If you insist on doing this, you also need to DELETE the pin
control back-end function
mtk_pinmux_gpio_set_direction(), which is what gets called.

Yours,
Linus Walleij