linux-kernel - Re: [PATCH v2] pinctrl: bcm63268: add gpio function

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Message-ID: <07a21d3f-539e-4609-bc60-ff320935db8a@gmail.com>
Date: Thu, 2 Jan 2025 19:04:49 -0800
From: Kyle Hendry <kylehendrydev@...il.com>
To: Jonas Gorski <jonas.gorski@...il.com>,
 Álvaro Fernández Rojas <noltari@...il.com>
Cc: linus.walleij@...aro.org, linux-gpio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] pinctrl: bcm63268: add gpio function

On 2024-12-30 08:42, Jonas Gorski wrote:
> Hi,
>
> On Tue, Dec 24, 2024 at 11:41 AM Álvaro Fernández Rojas
> <noltari@...il.com> wrote:
>> From: Kyle Hendry <kylehendrydev@...il.com>
>>
>> There is no guarantee that the bootloader will leave the pin configuration
>> in a known default state, so pinctrl needs to be explicitly set in some
>> cases. This patch adds a gpio function for drivers that need it, i.e.
>> gpio-leds.
>>
>> Signed-off-by: Kyle Hendry <kylehendrydev@...il.com>
>> Signed-off-by: Álvaro Fernández Rojas <noltari@...il.com>
>
> bcm63268-pinctrl implements pinmux_ops::gpio_request_enable(), which
> should automatically set any requested GPIO pin to the GPIO function,
> so explicitly requesting the gpio function for a pin should not be
> needed. Is this not enough?
>
> Best Regards,
> Jonas
>
>
I assumed that as well, but nothing I tried worked with gpio-leds.
gpiochip_generic_request() does call gpio_request_enable(), but gpio-leds
uses devm_fwnode_gpiod_get() which looks like a different code path. The
only place it seems to be configuring the gpio is in create_gpio_led()
where it needs a pinctl node in the device tree. That's just my reading
of the code, though. I haven't set up a ftrace to verify it.

Best Regards,
Kyle