From: Linus Walleij <linusw@kernel.org>
To: Chen-Yu Tsai <wenst@chromium.org>
Cc: Sean Wang <sean.wang@kernel.org>,
Matthias Brugger <matthias.bgg@gmail.com>,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@collabora.com>,
linux-mediatek@lists.infradead.org, linux-gpio@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] pinctrl: mediatek: paris: Directly modify registers to set GPIO direction
Date: Tue, 28 Apr 2026 12:44:37 +0200 [thread overview]
Message-ID: <CAD++jLnP9HvWPQg8WqoFkgRoFCWjkOUsRAgtnks4mEhHwYRt+g@mail.gmail.com> (raw)
In-Reply-To: <20260427021021.2049015-1-wenst@chromium.org>
On Mon, Apr 27, 2026 at 4:10 AM Chen-Yu Tsai <wenst@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@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
next prev parent reply other threads:[~2026-04-28 10:44 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-27 2:10 [PATCH] pinctrl: mediatek: paris: Directly modify registers to set GPIO direction Chen-Yu Tsai
2026-04-28 10:44 ` Linus Walleij [this message]
2026-04-29 9:03 ` Chen-Yu Tsai
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