linux-kernel - Re: [PATCH 1/2] pinctrl: Add Pistachio SoC pin control binding document

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Date:	Fri, 6 Mar 2015 12:37:09 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Andrew Bresticker <abrestic@...omium.org>
Cc:	Alexandre Courbot <gnurou@...il.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux MIPS <linux-mips@...ux-mips.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ezequiel Garcia <ezequiel.garcia@...tec.com>,
	James Hartley <james.hartley@...tec.com>,
	James Hogan <james.hogan@...tec.com>,
	Damien Horsley <Damien.Horsley@...tec.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>
Subject: Re: [PATCH 1/2] pinctrl: Add Pistachio SoC pin control binding document

On Tue, Feb 24, 2015 at 3:15 AM, Andrew Bresticker
<abrestic@...omium.org> wrote:

> Add a device-tree binding document for the pin controller present
> on the IMG Pistachio SoC.
>
> Signed-off-by: Damien Horsley <Damien.Horsley@...tec.com>
> Signed-off-by: Andrew Bresticker <abrestic@...omium.org>
(...)
> +Note that the GPIO bank sub-nodes *must* be listed in order.

Usually we use aliases to mark the order of things. e.g.:

        aliases {
                gpio0 = &gpio0;
                gpio1 = &gpio1;
                gpio2 = &gpio2;
                ethernet0 = &eth0;
                ethernet1 = &eth1;
        };

(arch/arm/boot/dts/armada-375.dtsi)

> +Required properties for pin configuration sub-nodes:
> +----------------------------------------------------
> + - pins: List of pins to which the configuration applies. See below for a
> +   list of possible pins.
> +
> +Optional properties for pin configuration sub-nodes:
> +----------------------------------------------------
> + - function: Mux function for the specified pins. This is not applicable for
> +   non-MFIO pins. See below for a list of valid functions for each pin.
> + - bias-high-impedance: Enable high-impedance mode.
> + - bias-pull-up: Enable weak pull-up.
> + - bias-pull-down: Enable weak pull-down.
> + - bias-bus-hold: Enable bus-keeper mode.
> + - drive-strength: Drive strength in mA. Supported values: 2, 4, 8, 12.
> + - input-schmitt-enable: Enable Schmitt trigger.
> + - input-schmitt-disable: Disable Schmitt trigger.
> + - slew-rate: Slew rate control. 0 for slow, 1 for fast.

We actually haven't specified that function+pins is a valid pattern,
a lot of drivers just started doing that :(

function+groups is documented for muxing.

group + config opts is documented for config.

Please consider patching the generic bindings to reflect this
mux use of pins... We need to discuss it.

Yours,
Linus Walleij
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