82 lines
2.5 KiB
Plaintext
82 lines
2.5 KiB
Plaintext
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 i2c-mux.txt in this directory.
|
|
* I2C child bus nodes. See i2c-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 relevant 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>;
|
|
};
|
|
};
|
|
};
|