projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| ae58d1e4 SW |
1 | Pinctrl-based I2C Bus Mux |
| 2 | ||
| 3 | This binding describes an I2C bus multiplexer that uses pin multiplexing to | |
| 4 | route the I2C signals, and represents the pin multiplexing configuration | |
| 5 | using the pinctrl device tree bindings. | |
| 6 | ||
| 7 | +-----+ +-----+ | |
| 8 | | dev | | dev | | |
| 9 | +------------------------+ +-----+ +-----+ | |
| 10 | | SoC | | | | |
| 11 | | /----|------+--------+ | |
| 12 | | +---+ +------+ | child bus A, on first set of pins | |
| 13 | | |I2C|---|Pinmux| | | |
| 14 | | +---+ +------+ | child bus B, on second set of pins | |
| 15 | | \----|------+--------+--------+ | |
| 16 | | | | | | | |
| 17 | +------------------------+ +-----+ +-----+ +-----+ | |
| 18 | | dev | | dev | | dev | | |
| 19 | +-----+ +-----+ +-----+ | |
| 20 | ||
| 21 | Required properties: | |
| 22 | - compatible: i2c-mux-pinctrl | |
| 23 | - i2c-parent: The phandle of the I2C bus that this multiplexer's master-side | |
| 24 | port is connected to. | |
| 25 | ||
| 26 | Also required are: | |
| 27 | ||
| 28 | * Standard pinctrl properties that specify the pin mux state for each child | |
| 29 | bus. See ../pinctrl/pinctrl-bindings.txt. | |
| 30 | ||
| 2e932849 | 31 | * Standard I2C mux properties. See i2c-mux.txt in this directory. |
| ae58d1e4 | 32 | |
| 2e932849 | 33 | * I2C child bus nodes. See i2c-mux.txt in this directory. |
| ae58d1e4 SW |
34 | |
| 35 | For each named state defined in the pinctrl-names property, an I2C child bus | |
| 36 | will be created. I2C child bus numbers are assigned based on the index into | |
| 37 | the pinctrl-names property. | |
| 38 | ||
| 39 | The only exception is that no bus will be created for a state named "idle". If | |
| 40 | such a state is defined, it must be the last entry in pinctrl-names. For | |
| 41 | example: | |
| 42 | ||
| 43 | pinctrl-names = "ddc", "pta", "idle" -> ddc = bus 0, pta = bus 1 | |
| 44 | pinctrl-names = "ddc", "idle", "pta" -> Invalid ("idle" not last) | |
| 45 | pinctrl-names = "idle", "ddc", "pta" -> Invalid ("idle" not last) | |
| 46 | ||
| 47 | Whenever an access is made to a device on a child bus, the relevant pinctrl | |
| 48 | state will be programmed into hardware. | |
| 49 | ||
| 50 | If an idle state is defined, whenever an access is not being made to a device | |
| 51 | on a child bus, the idle pinctrl state will be programmed into hardware. | |
| 52 | ||
| 53 | If an idle state is not defined, the most recently used pinctrl state will be | |
| 54 | left programmed into hardware whenever no access is being made of a device on | |
| 55 | a child bus. | |
| 56 | ||
| 57 | Example: | |
| 58 | ||
| 59 | i2cmux { | |
| 60 | compatible = "i2c-mux-pinctrl"; | |
| 61 | #address-cells = <1>; | |
| 62 | #size-cells = <0>; | |
| 63 | ||
| 64 | i2c-parent = <&i2c1>; | |
| 65 | ||
| 66 | pinctrl-names = "ddc", "pta", "idle"; | |
| 67 | pinctrl-0 = <&state_i2cmux_ddc>; | |
| 68 | pinctrl-1 = <&state_i2cmux_pta>; | |
| 69 | pinctrl-2 = <&state_i2cmux_idle>; | |
| 70 | ||
| 71 | i2c@0 { | |
| 72 | reg = <0>; | |
| 73 | #address-cells = <1>; | |
| 74 | #size-cells = <0>; | |
| 75 | ||
| 76 | eeprom { | |
| 77 | compatible = "eeprom"; | |
| 78 | reg = <0x50>; | |
| 79 | }; | |
| 80 | }; | |
| 81 | ||
| 82 | i2c@1 { | |
| 83 | reg = <1>; | |
| 84 | #address-cells = <1>; | |
| 85 | #size-cells = <0>; | |
| 86 | ||
| 87 | eeprom { | |
| 88 | compatible = "eeprom"; | |
| 89 | reg = <0x50>; | |
| 90 | }; | |
| 91 | }; | |
| 92 | }; | |
| 93 |