linux-kernel - Re: [PATCH RFC] gpiolib: ensure that fwnode is properly set

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Date:   Wed, 16 Nov 2022 06:14:01 -0500
From:   Brian Masney <bmasney@...hat.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     linus.walleij@...aro.org, brgl@...ev.pl,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, psodagud@...cinc.com,
        quic_shazhuss@...cinc.com, quic_ppareek@...cinc.com,
        ahalaney@...hat.com, echanude@...hat.com,
        nicolas.dechesne@...aro.org
Subject: Re: [PATCH RFC] gpiolib: ensure that fwnode is properly set

On Wed, Nov 16, 2022 at 11:21:37AM +0100, Thierry Reding wrote:
> On Mon, Nov 14, 2022 at 03:29:43PM -0500, Brian Masney wrote:
> > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > index 11fb7ec883e9..8bec66008869 100644
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -678,7 +678,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
> >  	 * Assign fwnode depending on the result of the previous calls,
> >  	 * if none of them succeed, assign it to the parent's one.
> >  	 */
> > -	gdev->dev.fwnode = dev_fwnode(&gdev->dev) ?: fwnode;
> > +	gc->fwnode = gdev->dev.fwnode = dev_fwnode(&gdev->dev) ?: fwnode;
> 
> This doesn't look right to me. Looking at the documentation of
> gc->fwnode and how it is used, the purpose of this is to allow
> explicitly overriding the fwnode that the GPIO chip will use.
> 
> So really this should not be used beyond the initial registration
> in gpiochip_add_data_with_key(). If the above patch fixes anything,
> then I suspect somebody is using gc->fwnode outside of this
> registration.
> 
> Looking at gpiolib, the only remaining place that seems to do this is
> the gpio-reserved-ranges handling code, in which case, the below on top
> of my initial patch might fix that. That might explain why MSM is still
> seeing issues.

That is correct. The Thinkpad x13s laptop uses the driver
drivers/pinctrl/qcom/pinctrl-sc8280xp.c and
arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts defines a
gpio-reserved-ranges property. The SA8540p automotive board has the same
SoC, however the DTS we are using doesn't use the gpio-reserved-ranges
property, and why only your original patch fixed the issue for this
board.

I think my patch should be removed from the GPIO tree if Thierry's two
patches work for everyone.

Brian