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

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Date:	Fri, 20 Dec 2013 12:52:31 +0100
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	linux-kernel@...r.kernel.org
Cc:	kernel@...gutronix.de, devicetree-discuss@...ts.ozlabs.org,
	Roger Quadros <rogerq@...com>,
	Mark Rutland <mark.rutland@....com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Philipp Zabel <p.zabel@...gutronix.de>
Subject: [PATCH 1/2] Documentation: Add GPIO reset binding to reset binding documentation

Signed-off-by: Philipp Zabel <p.zabel@...gutronix.de>
---
I'm not quite sure about whether the reset-gpio-names property should be used,
since the current GPIO scheme of prefixing the name would allow to add the
initially-in-reset property quite easily:
	reset-gpios = <&gpio3 15 GPIO_ACTIVE_LOW>, <&gpio5 12 GPIO_ACTIVE_HIGH>;
	reset-gpio-names = "core", "phy";
vs
	core-reset-gpios = <&gpio3 15 GPIO_ACTIVE_LOW>;
	phy-reset-gpios = <&gpio5 12 GPIO_ACTIVE_HIGH>;
	phy-reset-initially-asserted;
for example.
---
 Documentation/devicetree/bindings/reset/reset.txt | 26 +++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/reset/reset.txt b/Documentation/devicetree/bindings/reset/reset.txt
index 31db6ff..e40c6a7 100644
--- a/Documentation/devicetree/bindings/reset/reset.txt
+++ b/Documentation/devicetree/bindings/reset/reset.txt
@@ -2,8 +2,8 @@
 
 This binding is intended to represent the hardware reset signals present
 internally in most IC (SoC, FPGA, ...) designs. Reset signals for whole
-standalone chips are most likely better represented as GPIOs, although there
-are likely to be exceptions to this rule.
+standalone chips are most likely better represented as GPIOs, ideally using a
+common scheme as described below.
 
 Hardware blocks typically receive a reset signal. This signal is generated by
 a reset provider (e.g. power management or clock module) and received by a
@@ -56,6 +56,20 @@ reset-names:	List of reset signal name strings sorted in the same order as
 		the resets property. Consumers drivers will use reset-names to
 		match reset signal names with reset specifiers.
 
+= 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:		List of reset GPIOs using standard GPIO bindings.
+
+Optional properties:
+reset-gpio-names:	List of reset signal name strings sorted in the same
+			order as the reset-gpios property. Consumers drivers
+			will use reset-names to match reset signal names with
+			gpio-reset specifiers.
+
 For example:
 
 	device {
@@ -65,6 +79,14 @@ For example:
 
 This represents a device with a single reset signal named "reset".
 
+	device2 {
+		reset-gpios = <&gpio3 15 GPIO_ACTIVE_LOW>;
+		reset-gpio-names = "nreset";
+	};
+
+This represents a device with a single reset signal named "nreset", controlled
+by an active-low GPIO.
+
 	bus {
 		resets = <&rst 10> <&rst 11> <&rst 12> <&rst 11>;
 		reset-names = "i2s1", "i2s2", "dma", "mixer";
-- 
1.8.5.1

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