linux-kernel - Re: [PATCH v3 1/2] Documentation: Add GPIO reset binding to reset binding documentation

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Message-Id: <201401081708.26679.arnd@arndb.de>
Date:	Wed, 8 Jan 2014 17:08:26 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Philipp Zabel <p.zabel@...gutronix.de>
Cc:	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel@...gutronix.de, Roger Quadros <rogerq@...com>,
	Mark Rutland <mark.rutland@....com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Stephen Warren <swarren@...dotorg.org>
Subject: Re: [PATCH v3 1/2] Documentation: Add GPIO reset binding to reset binding documentation

On Wednesday 08 January 2014, Philipp Zabel wrote:
> += GPIO Reset consumers =
> +
> +For the common case of reset lines controlled by GPIOs, the GPIO binding
> +documented in devicetree/bindings/gpio/gpio.txt should be used:
> +
> +Required properties:
> +reset-gpios or         Reset GPIO using standard GPIO bindings,
> +<name>-reset-gpios:    optionally named to specify the reset line
> +
> +Optional properties:
> +reset-boot-asserted or         Boolean. If set, the corresponding reset is
> +<name>-reset-boot-asserted:    initially asserted and should be kept that way
> +                               until released by the driver.

I don't get this one. Why would you use a different reset binding for the case
where the reset line is connected to the gpio controller rather than a
specialized reset controller?

I was expecting to see the definition of a generic reset controller that
in turn uses gpio lines, like


	reset {	
		compatible = "gpio-reset";
		/* provides three reset lines through these GPIOs */
		gpios = <&gpioA 1 &gpioB 7 <gpioD 17>;
		#reset-cells = <1>;
	};

	foo {
		...
		resets = <&reset 0>; /* uses first reset line of the gpio-reset controller */
	};

I realize it would be a little more verbose, but it also seems more
regular and wouldn't stand out from the rest of the reset interfaces.

	Arnd
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