linux-kernel - [PATCH v4 1/2] Documentation: Add GPIO reset binding to reset binding documentation

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Message-Id: <1397463709-19405-1-git-send-email-p.zabel@pengutronix.de>
Date:	Mon, 14 Apr 2014 10:21:48 +0200
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	linux-kernel@...r.kernel.org,
	Arnd Bergmann Arnd Bergmann <arnd@...db.de>
Cc:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Mark Rutland <mark.rutland@....com>,
	Roger Quadros <rogerq@...com>,
	Stephen Warren <swarren@...dotorg.org>,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	kernel@...gutronix.de, Philipp Zabel <p.zabel@...gutronix.de>
Subject: [PATCH v4 1/2] Documentation: Add GPIO reset binding to reset binding documentation

This patch adds documentation clarifying the reset GPIO bindings most
commonly in use (reset-gpios and <name>-reset-gpios properties).

Signed-off-by: Philipp Zabel <p.zabel@...gutronix.de>
---
 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..51f9e35 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 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.
+
 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-boot-asserted;
+	};
+
+This represents a device with a single reset signal, controlled
+by an active-low GPIO, which is initally kept in reset.
+
 	bus {
 		resets = <&rst 10> <&rst 11> <&rst 12> <&rst 11>;
 		reset-names = "i2s1", "i2s2", "dma", "mixer";
-- 
1.9.1

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