linux-kernel - [PATCH v1 1/1] gpio: of: provide option generic property for initial line states

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Date:   Fri,  9 Jun 2017 16:16:22 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     kernel@...gutronix.de, Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, barebox@...ts.infradead.org
Cc:     Oleksij Rempel <o.rempel@...gutronix.de>
Subject: [PATCH v1 1/1] gpio: of: provide option generic property for initial line states

This property is needed for barebox or may be other bootloaders
to set proper gpio configuration as early as possible.

This example is mainly based on "lines-initial-states" property
from this binding documentation:
Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt

Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
---
 Documentation/devicetree/bindings/gpio/gpio.txt | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
index 84ede036f73d..60f8e8d8ab32 100644
--- a/Documentation/devicetree/bindings/gpio/gpio.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio.txt
@@ -181,6 +181,26 @@ gpio-controller@...00000 {
 		"poweroff", "reset";
 }
 
+Optionally, a GPIO controller may have a "gpio-lines-initial-states" property.
+This is an array of values that specifies the initial state of each line. When
+a value is set to one, the corresponding line will be initialized to the input
+(pulled-up) state. When the values is set to two, the line will be initialized
+the low-level output state. If values is set to zero the line will be
+initialized to the input state.
+If the property is not specified no specific configuration will be set. Driver
+should reuse HW configuration provided by bootloader or other system.
+
+Example:
+
+gpio-controller@...00000 {
+	compatible = "foo";
+	reg = <0x00000000 0x1000>;
+	gpio-controller;
+	#gpio-cells = <2>;
+	ngpios = <9>;
+	gpio-lines-initial-states = <0>, <1>, <2>, <0>, <0>, <2>, <2>, <1>, <1>;
+}
+
 The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism
 providing automatic GPIO request and configuration as part of the
 gpio-controller's driver probe function.
-- 
2.11.0