linux-kernel - Re: [PATCH v4] gpio: Return EPROBE_DEFER if gc->to

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Date:   Thu, 10 Feb 2022 19:00:07 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Shreeya Patel <shreeya.patel@...labora.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        wsa@...nel.org, 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>,
        kbuild test robot <lkp@...el.com>
Subject: Re: [PATCH v4] gpio: Return EPROBE_DEFER if gc->to_irq is NULL

On Thu, Feb 10, 2022 at 5:36 PM Gabriel Krisman Bertazi
<krisman@...labora.com> wrote:
>
> Shreeya Patel <shreeya.patel@...labora.com> writes:
>
> > 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.
> >
> > BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=209413
> > Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> > Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
> > Reported-by: kernel test robot <lkp@...el.com>
> > Signed-off-by: Shreeya Patel <shreeya.patel@...labora.com>
>
> Hi guys,
>
> This seems to not have reached the Linus tree on 5.17.  If I'm not
> mistaken, it also hasn't reached linux-next as of today. Is there
> anything I'm missing here?
>
> This is required to prevent spurious probe crashes of devices like this
> FocalTech touchscreen, FT3528, when using pinctrl-amd. We've been
> carrying it downstream for quite a while.
>
> Thanks,
>
> --
> Gabriel Krisman Bertazi

Hi Gabriel!

My email address changed in September, that's why I didn't see the
email you sent in November to my old one.

gpiod_to_irq() can be used in context other than driver probing, I'm
worried existing users would not know how to handle it. Also: how come
you can get the GPIO descriptor from the provider but its interrupts
are not yet set up?

Bart