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

[Chen-Yu Tsai]

On Tue, Apr 28, 2026 at 7:44 PM Linus Walleij <linusw at kernel.org> wrote:
>
> 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?

This is essentially following

    commit 8df89a7cbc63 ("pinctrl-sunxi: don't call pinctrl_gpio_direction()")

And in MediaTek's hardware, the GPIO direction is even further removed
from pinctrl. GPIO is a function that gets muxed, but after that the
direction and data bits are in separate registers that are grouped
separately from the pinmux registers. The pin controller doesn't have
to be involved.

> 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.

You mean delete the .gpio_set_direction field from pinmux_ops?
Sure I can do that.


Thanks
ChenYu