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authorMaxime Ripard <maxime.ripard@free-electrons.com>2012-10-25 18:23:53 +0200
committerWolfram Sang <w.sang@pengutronix.de>2012-11-16 09:28:27 +0100
commit9b7a0c40de6c5c04371f8cdb9153a0a5a0af5243 (patch)
tree02a02f2c3b38e8504d58a2eb4e4fa815804faf78 /Documentation
parent29fb08c300b5cb626b8a803440aab25d0983cab7 (diff)
downloadop-kernel-dev-9b7a0c40de6c5c04371f8cdb9153a0a5a0af5243.zip
op-kernel-dev-9b7a0c40de6c5c04371f8cdb9153a0a5a0af5243.tar.gz
i2c: mux: Add dt support to i2c-mux-gpio driver
Allow the i2c-mux-gpio to be used by a device tree enabled device. The bindings are inspired by the one found in the i2c-mux-pinctrl driver. Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> Reviewed-by: Stephen Warren <swarren@nvidia.com> Acked-by: Peter Korsgaard <peter.korsgaard@barco.com> [wsa: fixed some whitespace] Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/devicetree/bindings/i2c/i2c-mux-gpio.txt81
1 files changed, 81 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-gpio.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-gpio.txt
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index 0000000..66709a8
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+++ b/Documentation/devicetree/bindings/i2c/i2c-mux-gpio.txt
@@ -0,0 +1,81 @@
+GPIO-based I2C Bus Mux
+
+This binding describes an I2C bus multiplexer that uses GPIOs to
+route the I2C signals.
+
+ +-----+ +-----+
+ | dev | | dev |
+ +------------+ +-----+ +-----+
+ | SoC | | |
+ | | /--------+--------+
+ | +------+ | +------+ child bus A, on GPIO value set to 0
+ | | I2C |-|--| Mux |
+ | +------+ | +--+---+ child bus B, on GPIO value set to 1
+ | | | \----------+--------+--------+
+ | +------+ | | | | |
+ | | GPIO |-|-----+ +-----+ +-----+ +-----+
+ | +------+ | | dev | | dev | | dev |
+ +------------+ +-----+ +-----+ +-----+
+
+Required properties:
+- compatible: i2c-mux-gpio
+- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side
+ port is connected to.
+- mux-gpios: list of gpios used to control the muxer
+* Standard I2C mux properties. See mux.txt in this directory.
+* I2C child bus nodes. See mux.txt in this directory.
+
+Optional properties:
+- idle-state: value to set the muxer to when idle. When no value is
+ given, it defaults to the last value used.
+
+For each i2c child node, an I2C child bus will be created. They will
+be numbered based on their order in the device tree.
+
+Whenever an access is made to a device on a child bus, the value set
+in the revelant node's reg property will be output using the list of
+GPIOs, the first in the list holding the least-significant value.
+
+If an idle state is defined, using the idle-state (optional) property,
+whenever an access is not being made to a device on a child bus, the
+GPIOs will be set according to the idle value.
+
+If an idle state is not defined, the most recently used value will be
+left programmed into hardware whenever no access is being made to a
+device on a child bus.
+
+Example:
+ i2cmux {
+ compatible = "i2c-mux-gpio";
+ #address-cells = <1>;
+ #size-cells = <0>;
+ mux-gpios = <&gpio1 22 0 &gpio1 23 0>;
+ i2c-parent = <&i2c1>;
+
+ i2c@1 {
+ reg = <1>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ ssd1307: oled@3c {
+ compatible = "solomon,ssd1307fb-i2c";
+ reg = <0x3c>;
+ pwms = <&pwm 4 3000>;
+ reset-gpios = <&gpio2 7 1>;
+ reset-active-low;
+ };
+ };
+
+ i2c@3 {
+ reg = <3>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ pca9555: pca9555@20 {
+ compatible = "nxp,pca9555";
+ gpio-controller;
+ #gpio-cells = <2>;
+ reg = <0x20>;
+ };
+ };
+ };
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