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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>
94 lines
2.8 KiB
Plaintext
94 lines
2.8 KiB
Plaintext
Pinctrl-based I2C Bus Mux
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This binding describes an I2C bus multiplexer that uses pin multiplexing to
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route the I2C signals, and represents the pin multiplexing configuration
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using the pinctrl device tree bindings.
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+-----+ +-----+
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| dev | | dev |
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+------------------------+ +-----+ +-----+
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| SoC | | |
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| /----|------+--------+
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| +---+ +------+ | child bus A, on first set of pins
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| |I2C|---|Pinmux| |
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| +---+ +------+ | child bus B, on second set of pins
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| \----|------+--------+--------+
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| | | | |
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+------------------------+ +-----+ +-----+ +-----+
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| dev | | dev | | dev |
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+-----+ +-----+ +-----+
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Required properties:
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- compatible: i2c-mux-pinctrl
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- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side
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port is connected to.
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Also required are:
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* Standard pinctrl properties that specify the pin mux state for each child
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bus. See ../pinctrl/pinctrl-bindings.txt.
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* Standard I2C mux properties. See mux.txt in this directory.
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* I2C child bus nodes. See mux.txt in this directory.
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For each named state defined in the pinctrl-names property, an I2C child bus
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will be created. I2C child bus numbers are assigned based on the index into
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the pinctrl-names property.
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The only exception is that no bus will be created for a state named "idle". If
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such a state is defined, it must be the last entry in pinctrl-names. For
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example:
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pinctrl-names = "ddc", "pta", "idle" -> ddc = bus 0, pta = bus 1
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pinctrl-names = "ddc", "idle", "pta" -> Invalid ("idle" not last)
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pinctrl-names = "idle", "ddc", "pta" -> Invalid ("idle" not last)
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Whenever an access is made to a device on a child bus, the relevant pinctrl
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state will be programmed into hardware.
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If an idle state is defined, whenever an access is not being made to a device
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on a child bus, the idle pinctrl state will be programmed into hardware.
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If an idle state is not defined, the most recently used pinctrl state will be
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left programmed into hardware whenever no access is being made of a device on
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a child bus.
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Example:
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i2cmux {
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compatible = "i2c-mux-pinctrl";
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#address-cells = <1>;
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#size-cells = <0>;
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i2c-parent = <&i2c1>;
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pinctrl-names = "ddc", "pta", "idle";
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pinctrl-0 = <&state_i2cmux_ddc>;
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pinctrl-1 = <&state_i2cmux_pta>;
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pinctrl-2 = <&state_i2cmux_idle>;
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i2c@0 {
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reg = <0>;
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#address-cells = <1>;
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#size-cells = <0>;
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eeprom {
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compatible = "eeprom";
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reg = <0x50>;
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};
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};
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i2c@1 {
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reg = <1>;
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#address-cells = <1>;
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#size-cells = <0>;
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eeprom {
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compatible = "eeprom";
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reg = <0x50>;
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};
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};
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};
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