[RESEND PATCH] pinctrl: mediatek: use spin lock in mtk_rmw

[Andy Shevchenko]

On Mon, Apr 19, 2021 at 8:32 AM Tzung-Bi Shih <tzungbi at google.com> wrote:
>
> Commit 42a46434e9b1 ("pinctrl: add lock in mtk_rmw function.") uses
> mutex lock in mtk_rmw.  However the function is possible called from
> atomic context.
>
> For example call trace:

Please, shrink it to the necessary minimum.

>   mutex_lock+0x28/0x64
>   mtk_rmw+0x38/0x80
>   mtk_hw_set_value+0x100/0x138
>   mtk_gpio_set+0x48/0x58
>   gpiod_set_raw_value_commit+0xf4/0x110
>   gpiod_set_value_nocheck+0x4c/0x80
>   gpiod_set_value+0x4c/0x6c
>   max98357a_daiops_trigger+0x8c/0x9c
>   soc_pcm_trigger+0x5c/0x10c
>
> The max98357a_daiops_trigger() could run in either atomic or non-atomic
> context.  As a result, dmesg shows some similar messages: "BUG: sleeping
> function called from invalid context at kernel/locking/mutex.c:254".
>
> Uses spin lock in mtk_rmw instead.

It's nice, but now the question is, can you have this function be
called in a non-IRQ context concurrently with IRQ accessing registers?


-- 
With Best Regards,
Andy Shevchenko