linux-kernel - Re: [PATCH v1 1/3] gpio: defer probe if pinctrl cannot be found

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Message-ID: <CAMuHMdXfKD200tpcJdxBrmwFQhyYLiptOxHOXKLRM9eRfJ9uqg@mail.gmail.com>
Date:	Thu, 2 Jul 2015 10:59:45 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Rob Herring <robherring2@...il.com>
Cc:	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCH v1 1/3] gpio: defer probe if pinctrl cannot be found

Hi Rob,

On Wed, Jul 1, 2015 at 7:36 PM, Rob Herring <robherring2@...il.com> wrote:
> On Wed, Jul 1, 2015 at 7:45 AM, Tomeu Vizoso <tomeu.vizoso@...labora.com> wrote:
>> When an OF node has a pin range for its GPIOs, return -EPROBE_DEFER if
>> the pin controller isn't available.
>>
>> Otherwise, the GPIO range wouldn't be set at all unless the pin
>> controller probed always before the GPIO chip.
>>
>> With this change, the probe of the GPIO chip will be deferred and will
>> be retried at a later point, hopefully once the pin controller has been
>> registered and probed already.
>
> This will break cases where the pinctrl driver does not exist, but the
> DT contains pinctrl bindings. We can have similar problems already
> with clocks though. However, IMO this problem is a bit different in
> that pinctrl is more likely entirely optional while clocks are often
> required. You may do all pin setup in bootloader/firmware on some
> boards and not others. Of course then why put pinctrl in the DT in
> that case? They could be present just due to how chip vs. board dts
> files are structured.

Isn't that already the case?
If I change the compatible value of a pinctrl node to an invalid value, I get:

    sh-sci e6c50000.serial: could not find pctldev for node
/pfc@...50000/serial1, deferring probe

> We could address this by simply marking the pin controller node
> disabled. However, ...

Doesn't seem to make any difference.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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