From 1821355188f14430fdcc75f6f6062c7cbae9e719 Mon Sep 17 00:00:00 2001 From: Peter Rosin Date: Sun, 14 May 2017 21:51:11 +0200 Subject: [PATCH] dt-bindings: i2c: i2c-mux: document general purpose i2c-mux bindings Describe how a general purpose multiplexer controller is used to mux an i2c bus. Acked-by: Jonathan Cameron Reviewed-by: Rob Herring Signed-off-by: Peter Rosin Signed-off-by: Greg Kroah-Hartman --- .../devicetree/bindings/i2c/i2c-mux-gpmux.txt | 99 ++++++++++++++++++++++ 1 file changed, 99 insertions(+) create mode 100644 Documentation/devicetree/bindings/i2c/i2c-mux-gpmux.txt diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-gpmux.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-gpmux.txt new file mode 100644 index 0000000..2907dab --- /dev/null +++ b/Documentation/devicetree/bindings/i2c/i2c-mux-gpmux.txt @@ -0,0 +1,99 @@ +General Purpose I2C Bus Mux + +This binding describes an I2C bus multiplexer that uses a mux controller +from the mux subsystem to route the I2C signals. + + .-----. .-----. + | dev | | dev | + .------------. '-----' '-----' + | SoC | | | + | | .--------+--------' + | .------. | .------+ child bus A, on MUX value set to 0 + | | I2C |-|--| Mux | + | '------' | '--+---+ child bus B, on MUX value set to 1 + | .------. | | '----------+--------+--------. + | | MUX- | | | | | | + | | Ctrl |-|-----+ .-----. .-----. .-----. + | '------' | | dev | | dev | | dev | + '------------' '-----' '-----' '-----' + +Required properties: +- compatible: i2c-mux +- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side + port is connected to. +- mux-controls: The phandle of the mux controller to use for operating the + mux. +* Standard I2C mux properties. See i2c-mux.txt in this directory. +* I2C child bus nodes. See i2c-mux.txt in this directory. The sub-bus number + is also the mux-controller state described in ../mux/mux-controller.txt + +Optional properties: +- mux-locked: If present, explicitly allow unrelated I2C transactions on the + parent I2C adapter at these times: + + during setup of the multiplexer + + between setup of the multiplexer and the child bus I2C transaction + + between the child bus I2C transaction and releasing of the multiplexer + + during releasing of the multiplexer + However, I2C transactions to devices behind all I2C multiplexers connected + to the same parent adapter that this multiplexer is connected to are blocked + for the full duration of the complete multiplexed I2C transaction (i.e. + including the times covered by the above list). + If mux-locked is not present, the multiplexer is assumed to be parent-locked. + This means that no unrelated I2C transactions are allowed on the parent I2C + adapter for the complete multiplexed I2C transaction. + The properties of mux-locked and parent-locked multiplexers are discussed + in more detail in Documentation/i2c/i2c-topology. + +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 relevant node's reg property will be set as the state in the +mux controller. + +Example: + mux: mux-controller { + compatible = "gpio-mux"; + #mux-control-cells = <0>; + + mux-gpios = <&pioA 0 GPIO_ACTIVE_HIGH>, + <&pioA 1 GPIO_ACTIVE_HIGH>; + }; + + i2c-mux { + compatible = "i2c-mux"; + mux-locked; + i2c-parent = <&i2c1>; + + mux-controls = <&mux>; + + #address-cells = <1>; + #size-cells = <0>; + + 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>; + }; + }; + }; -- 2.7.4