linux-kernel - Re: [PATCH v2] gpio: Return EPROBE_DEFER if gc->to

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Date:   Thu, 11 Nov 2021 22:58:48 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Shreeya Patel <shreeya.patel@...labora.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Wolfram Sang <wsa@...nel.org>, krisman@...labora.com,
        Sebastian Reichel <sebastian.reichel@...labora.com>,
        Collabora Kernel ML <kernel@...labora.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-i2c <linux-i2c@...r.kernel.org>
Subject: Re: [PATCH v2] gpio: Return EPROBE_DEFER if gc->to_irq is NULL

On Tue, Oct 19, 2021 at 1:07 AM Shreeya Patel
<shreeya.patel@...labora.com> wrote:
>
> We are racing the registering of .to_irq when probing the
> i2c driver. This results in random failure of touchscreen
> devices.
>
> Following errors could be seen in dmesg logs when gc->to_irq is NULL
>
> [2.101857] i2c_hid i2c-FTS3528:00: HID over i2c has not been provided an Int IRQ
> [2.101953] i2c_hid: probe of i2c-FTS3528:00 failed with error -22
>
> To avoid this situation, defer probing until to_irq is registered.
>
> This issue has been reported many times in past and people have been
> using workarounds like changing the pinctrl_amd to built-in instead
> of loading it as a module or by adding a softdep for pinctrl_amd into
> the config file.

> References :-
> https://bugzilla.kernel.org/show_bug.cgi?id=209413
> https://github.com/Syniurge/i2c-amd-mp2/issues/3

Please, convert them to BugLink: tags.

> Signed-off-by: Shreeya Patel <shreeya.patel@...labora.com>

...

> +       if (gc->irq.chip) {
> +               /* avoid race condition with other code, which tries to lookup
> +                * an IRQ before the irqchip has been properly registered
> +                * (i.e. while gpiochip is still being brought up).
> +                */

/*
 * The style of multi-line comments should be
 * like this. Pay attention to the grammar.
 * In your comment the parentheses can be replaced
 * by a simple ',' (comma without quotes).
 */

> +               return -EPROBE_DEFER;
> +       }


With above (including kbuildbot thingy) addressed
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

-- 
With Best Regards,
Andy Shevchenko