linux-kernel - Re: [PATCH 18/23] gpio: nomadik: support mobileye,eyeq5-gpio

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Message-Id: <CZBI90SFODAR.TZ3L2XO2F8IF@bootlin.com>
Date: Thu, 22 Feb 2024 10:37:18 +0100
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: "Linus Walleij" <linus.walleij@...aro.org>
Cc: "Bartosz Golaszewski" <brgl@...ev.pl>, "Rob Herring"
 <robh+dt@...nel.org>, "Krzysztof Kozlowski"
 <krzysztof.kozlowski+dt@...aro.org>, "Conor Dooley" <conor+dt@...nel.org>,
 "Philipp Zabel" <p.zabel@...gutronix.de>, "Thomas Bogendoerfer"
 <tsbogend@...ha.franken.de>, <linux-gpio@...r.kernel.org>,
 <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
 <linux-arm-kernel@...ts.infradead.org>, <linux-mips@...r.kernel.org>,
 "Gregory CLEMENT" <gregory.clement@...tlin.com>, "Vladimir Kondratiev"
 <vladimir.kondratiev@...ileye.com>, "Thomas Petazzoni"
 <thomas.petazzoni@...tlin.com>, "Tawfik Bayouk"
 <tawfik.bayouk@...ileye.com>
Subject: Re: [PATCH 18/23] gpio: nomadik: support mobileye,eyeq5-gpio

Hello,

On Wed Feb 21, 2024 at 8:36 PM CET, Linus Walleij wrote:
> On Wed, Feb 21, 2024 at 5:16 PM Théo Lebrun <theo.lebrun@...tlin.com> wrote:
>
> > > Trying to figure it out...
> >
> > Can I help in the debugging process?
>
> Nah, I found it :)
>
> > Reading the code once again I'd guess
> > of_device_get_match_data(&gpio_pdev->dev) could be the root cause. We
> > are accessing match data for the GPIO device while probing the pinctrl
> > device. Maybe something isn't initialised properly yet? The rest looks
> > rather harmless, I've checked all conditional expressions.
>
> Yep spot on. The nmk_gpio_populate_chip() is sometimes called from
> the pinctrl driver before the gpio probe() has been called, so the match
> data is NULL and we crash.
>
> This looks like it does for historical reasons and there could be better
> ways to fix it now that Saravana Kannan has fixed up the probe ordering
> code.
>
> The following is one way to fix it for now using device_is_compatible()
> (illustrating some other changes I did as well):

Thanks for the debugging and the proposed fix. Indeed matching on
compatible to avoid match data for a bool makes sense.

Thanks,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com