linux-kernel - Re: pinctrl-sx150x.c broken in 4.11

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Message-ID: <252b379a-d3fe-8020-5209-f1de43004b08@cogentembedded.com>
Date:   Thu, 11 May 2017 19:24:22 +0300
From:   Nikita Yushchenko <nikita.yoush@...entembedded.com>
To:     Tony Lindgren <tony@...mide.com>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Andrey Smirnov <andrew.smirnov@...il.com>,
        Chris Healy <Chris.Healy@....aero>,
        Jeff White <Jeff.White@....aero>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: pinctrl-sx150x.c broken in 4.11

> Hmm maybe yeah. I don't quite follow the above the "pinctrl-0 property
> of sx150x device tree node, is misinterpreted as hog" part though.

sx150x is i2c-gpio device.  It has 16 GPIO lines that are communicated
with via i2c bus, and an interrupt line.

Interrupt line is typically connected to SoC's pin.
This pin has to be configured.
This is done by providing appropriate subnode in SoC's pinmux node, with
information with pin configuration, and pinctrl-0 property in sx150x's
node with phandle to that subnode:

...
&i2c0 {
	sx1503@20 {
		compatible = "semtech,sx1503q";
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_sx1503_20>;
		...
	};
};
...
&iomuxc {
	pinctrl_sx1503_20: pinctrl-sx1503-20 {
		fsl,pins = <
			VF610_PAD_PTB1__GPIO_23         0x219d
		>;
	};
};

This pin configuration is handled by driver core, i.e. before probe()
for sx150x is called, core applies pin configuration.

However sx150x driver is currently implemented as a pinctrl driver.

When it initializes, pinctrl searches for "hog", i.e. pin config that
should be applied at driver registration time.

While doing so, core searches for any registered pinctrl_map for device
being register. Search loop is in create_pinctrl().

In this case, this loop finds map that is defined above.

This is *not* hog.  This is pin setting already applied in SoC's pinmux
controller for sx1503 device.

However code in create_pinctrl() tries to apply it, and use sx1503's
methods to do so. Which is plain wrong and errors out.

> But at least with updating the probe to use pinctrl_register_and_init()
> and pinctrl_enable() the driver can do something before the hogs are
> claimed. I just don't know what the driver would here as I don't
> understand the "misinterpreted as hog" part :)

Tried to explain above :)

I don't know whar can be done in sx1503 driver to avoid that scenario...
perhaps port it back from pinctrl subsystem to gpio subsystem.  However
I guess it was ported to pinctrl subsystem for a reason (that I don't know).

> Anyways, care to test if the following patch fixes the issue somehow?

No that patch does not help here.

Nikita