75 lines
2.4 KiB
Plaintext
75 lines
2.4 KiB
Plaintext
|
Register-based I2C Bus Mux
|
||
|
|
|
||
|
|
This binding describes an I2C bus multiplexer that uses a single register
|
||
|
|
to route the I2C signals.
|
||
|
|
|
||
|
|
Required properties:
|
||
|
|
- compatible: i2c-mux-reg
|
||
|
|
- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side
|
||
|
|
port is connected to.
|
||
|
|
* Standard I2C mux properties. See i2c-mux.txt in this directory.
|
||
|
|
* I2C child bus nodes. See i2c-mux.txt in this directory.
|
||
|
|
|
||
|
|
Optional properties:
|
||
|
|
- reg: this pair of <offset size> specifies the register to control the mux.
|
||
|
|
The <offset size> depends on its parent node. It can be any memory-mapped
|
||
|
|
address. The size must be either 1, 2, or 4 bytes. If reg is omitted, the
|
||
|
|
resource of this device will be used.
|
||
|
|
- little-endian: The existence indicates the register is in little endian.
|
||
|
|
- big-endian: The existence indicates the register is in big endian.
|
||
|
|
If both little-endian and big-endian are omitted, the endianness of the
|
||
|
|
CPU will be used.
|
||
|
|
- write-only: The existence indicates the register is write-only.
|
||
|
|
- idle-state: value to set the muxer to when idle. When no value is
|
||
|
|
given, it defaults to the last value used.
|
||
|
|
|
||
|
|
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 to the register.
|
||
|
|
|
||
|
|
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
|
||
|
|
register 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 the register.
|
||
|
|
|
||
|
|
Example of a mux on PCIe card, the host is a powerpc SoC (big endian):
|
||
|
|
|
||
|
|
i2c-mux {
|
||
|
|
/* the <offset size> depends on the address translation
|
||
|
|
* of the parent device. If omitted, device resource
|
||
|
|
* will be used instead. The size is to determine
|
||
|
|
* whether iowrite32, iowrite16, or iowrite8 will be used.
|
||
|
|
*/
|
||
|
|
reg = <0x6028 0x4>;
|
||
|
|
little-endian; /* little endian register on PCIe */
|
||
|
|
compatible = "i2c-mux-reg";
|
||
|
|
#address-cells = <1>;
|
||
|
|
#size-cells = <0>;
|
||
|
|
i2c-parent = <&i2c1>;
|
||
|
|
i2c@0 {
|
||
|
|
reg = <0>;
|
||
|
|
#address-cells = <1>;
|
||
|
|
#size-cells = <0>;
|
||
|
|
|
||
|
|
si5338: clock-generator@70 {
|
||
|
|
compatible = "silabs,si5338";
|
||
|
|
reg = <0x70>;
|
||
|
|
/* other stuff */
|
||
|
|
};
|
||
|
|
};
|
||
|
|
|
||
|
|
i2c@1 {
|
||
|
|
/* data is written using iowrite32 */
|
||
|
|
reg = <1>;
|
||
|
|
#address-cells = <1>;
|
||
|
|
#size-cells = <0>;
|
||
|
|
|
||
|
|
si5338: clock-generator@70 {
|
||
|
|
compatible = "silabs,si5338";
|
||
|
|
reg = <0x70>;
|
||
|
|
/* other stuff */
|
||
|
|
};
|
||
|
|
};
|
||
|
|
};
|