xref: /freebsd/sys/contrib/device-tree/Bindings/i2c/i2c-demux-pinctrl.txt (revision cab6a39d7b343596a5823e65c0f7b426551ec22d) 
1Pinctrl-based I2C Bus DeMux
2
3This binding describes an I2C bus demultiplexer that uses pin multiplexing to
4route the I2C signals, and represents the pin multiplexing configuration using
5the pinctrl device tree bindings. This may be used to select one I2C IP core at
6runtime which may have a better feature set for a given task than another I2C
7IP core on the SoC. The most simple example is to fall back to GPIO bitbanging
8if your current runtime configuration hits an errata of the internal IP core.
9
10    +-------------------------------+
11    | SoC                           |
12    |                               |   +-----+  +-----+
13    |   +------------+              |   | dev |  | dev |
14    |   |I2C IP Core1|--\           |   +-----+  +-----+
15    |   +------------+   \-------+  |      |        |
16    |                    |Pinctrl|--|------+--------+
17    |   +------------+   +-------+  |
18    |   |I2C IP Core2|--/           |
19    |   +------------+              |
20    |                               |
21    +-------------------------------+
22
23Required properties:
24- compatible: "i2c-demux-pinctrl"
25- i2c-parent: List of phandles of I2C masters available for selection. The first
26	      one will be used as default.
27- i2c-bus-name: The name of this bus. Also needed as pinctrl-name for the I2C
28		parents.
29
30Furthermore, I2C mux properties and child nodes. See i2c-mux.txt in this
31directory.
32
33Example:
34
35Here is a snipplet for a bus to be demuxed. It contains various i2c clients for
36HDMI, so the bus is named "i2c-hdmi":
37
38	i2chdmi: i2c@8 {
39
40		compatible = "i2c-demux-pinctrl";
41		i2c-parent = <&gpioi2c>, <&iic2>, <&i2c2>;
42		i2c-bus-name = "i2c-hdmi";
43		#address-cells = <1>;
44		#size-cells = <0>;
45
46		ak4643: sound-codec@12 {
47			compatible = "asahi-kasei,ak4643";
48
49			#sound-dai-cells = <0>;
50			reg = <0x12>;
51		};
52
53		composite-in@20 {
54			compatible = "adi,adv7180";
55			reg = <0x20>;
56			remote = <&vin1>;
57
58			port {
59				adv7180: endpoint {
60					bus-width = <8>;
61					remote-endpoint = <&vin1ep0>;
62				};
63			};
64		};
65
66		hdmi@39 {
67			compatible = "adi,adv7511w";
68			reg = <0x39>;
69			interrupt-parent = <&gpio1>;
70			interrupts = <15 IRQ_TYPE_LEVEL_LOW>;
71
72			adi,input-depth = <8>;
73			adi,input-colorspace = "rgb";
74			adi,input-clock = "1x";
75			adi,input-style = <1>;
76			adi,input-justification = "evenly";
77
78			ports {
79				#address-cells = <1>;
80				#size-cells = <0>;
81
82				port@0 {
83					reg = <0>;
84					adv7511_in: endpoint {
85						remote-endpoint = <&du_out_lvds0>;
86					};
87				};
88
89				port@1 {
90					reg = <1>;
91					adv7511_out: endpoint {
92						remote-endpoint = <&hdmi_con>;
93					};
94				};
95			};
96		};
97	};
98
99And for clarification, here are the snipplets for the i2c-parents:
100
101	gpioi2c: i2c@9 {
102		#address-cells = <1>;
103		#size-cells = <0>;
104		compatible = "i2c-gpio";
105		gpios = <&gpio5 6 GPIO_ACTIVE_HIGH /* sda */
106			 &gpio5 5 GPIO_ACTIVE_HIGH /* scl */
107			>;
108		i2c-gpio,delay-us = <5>;
109	};
110
111...
112
113&i2c2	{
114	pinctrl-0 = <&i2c2_pins>;
115	pinctrl-names = "i2c-hdmi";
116
117	clock-frequency = <100000>;
118};
119
120...
121
122&iic2	{
123	pinctrl-0 = <&iic2_pins>;
124	pinctrl-names = "i2c-hdmi";
125
126	clock-frequency = <100000>;
127};
128
129Please note:
130
131- pinctrl properties for the parent I2C controllers need a pinctrl state
132  with the same name as i2c-bus-name, not "default"!
133
134- the i2c masters must have their status "disabled". This driver will
135  enable them at runtime when needed.
136