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author | Stephen Warren <swarren@nvidia.com> | 2012-05-18 17:29:34 +0200 |
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committer | Wolfram Sang <w.sang@pengutronix.de> | 2012-06-04 16:49:43 +0200 |
commit | ae58d1e406986f31d1e88b32f5ac601506c196d8 (patch) | |
tree | 85f8973189b8e7bab81bdc235eeb1fb48176bb9d /Documentation | |
parent | Linux 3.5-rc1 (diff) | |
download | linux-ae58d1e406986f31d1e88b32f5ac601506c196d8.tar.xz linux-ae58d1e406986f31d1e88b32f5ac601506c196d8.zip |
i2c: Add generic I2C multiplexer using pinctrl API
This is useful for SoCs whose I2C module's signals can be routed to
different sets of pins at run-time, using the pinctrl API.
+-----+ +-----+
| dev | | dev |
+------------------------+ +-----+ +-----+
| SoC | | |
| /----|------+--------+
| +---+ +------+ | child bus A, on first set of pins
| |I2C|---|Pinmux| |
| +---+ +------+ | child bus B, on second set of pins
| \----|------+--------+--------+
| | | | |
+------------------------+ +-----+ +-----+ +-----+
| dev | | dev | | dev |
+-----+ +-----+ +-----+
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt new file mode 100644 index 000000000000..ae8af1694e95 --- /dev/null +++ b/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt @@ -0,0 +1,93 @@ +Pinctrl-based I2C Bus Mux + +This binding describes an I2C bus multiplexer that uses pin multiplexing to +route the I2C signals, and represents the pin multiplexing configuration +using the pinctrl device tree bindings. + + +-----+ +-----+ + | dev | | dev | + +------------------------+ +-----+ +-----+ + | SoC | | | + | /----|------+--------+ + | +---+ +------+ | child bus A, on first set of pins + | |I2C|---|Pinmux| | + | +---+ +------+ | child bus B, on second set of pins + | \----|------+--------+--------+ + | | | | | + +------------------------+ +-----+ +-----+ +-----+ + | dev | | dev | | dev | + +-----+ +-----+ +-----+ + +Required properties: +- compatible: i2c-mux-pinctrl +- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side + port is connected to. + +Also required are: + +* Standard pinctrl properties that specify the pin mux state for each child + bus. See ../pinctrl/pinctrl-bindings.txt. + +* Standard I2C mux properties. See mux.txt in this directory. + +* I2C child bus nodes. See mux.txt in this directory. + +For each named state defined in the pinctrl-names property, an I2C child bus +will be created. I2C child bus numbers are assigned based on the index into +the pinctrl-names property. + +The only exception is that no bus will be created for a state named "idle". If +such a state is defined, it must be the last entry in pinctrl-names. For +example: + + pinctrl-names = "ddc", "pta", "idle" -> ddc = bus 0, pta = bus 1 + pinctrl-names = "ddc", "idle", "pta" -> Invalid ("idle" not last) + pinctrl-names = "idle", "ddc", "pta" -> Invalid ("idle" not last) + +Whenever an access is made to a device on a child bus, the relevant pinctrl +state will be programmed into hardware. + +If an idle state is defined, whenever an access is not being made to a device +on a child bus, the idle pinctrl state will be programmed into hardware. + +If an idle state is not defined, the most recently used pinctrl state will be +left programmed into hardware whenever no access is being made of a device on +a child bus. + +Example: + + i2cmux { + compatible = "i2c-mux-pinctrl"; + #address-cells = <1>; + #size-cells = <0>; + + i2c-parent = <&i2c1>; + + pinctrl-names = "ddc", "pta", "idle"; + pinctrl-0 = <&state_i2cmux_ddc>; + pinctrl-1 = <&state_i2cmux_pta>; + pinctrl-2 = <&state_i2cmux_idle>; + + i2c@0 { + reg = <0>; + #address-cells = <1>; + #size-cells = <0>; + + eeprom { + compatible = "eeprom"; + reg = <0x50>; + }; + }; + + i2c@1 { + reg = <1>; + #address-cells = <1>; + #size-cells = <0>; + + eeprom { + compatible = "eeprom"; + reg = <0x50>; + }; + }; + }; + |