1 Register-based I2C Bus Mux 1 Register-based I2C Bus Mux
2 2
3 This binding describes an I2C bus multiplexer 3 This binding describes an I2C bus multiplexer that uses a single register
4 to route the I2C signals. 4 to route the I2C signals.
5 5
6 Required properties: 6 Required properties:
7 - compatible: i2c-mux-reg 7 - compatible: i2c-mux-reg
8 - i2c-parent: The phandle of the I2C bus that 8 - i2c-parent: The phandle of the I2C bus that this multiplexer's master-side
9 port is connected to. 9 port is connected to.
10 * Standard I2C mux properties. See i2c-mux.yam 10 * Standard I2C mux properties. See i2c-mux.yaml in this directory.
11 * I2C child bus nodes. See i2c-mux.yaml in thi 11 * I2C child bus nodes. See i2c-mux.yaml in this directory.
12 12
13 Optional properties: 13 Optional properties:
14 - reg: this pair of <offset size> specifies th 14 - reg: this pair of <offset size> specifies the register to control the mux.
15 The <offset size> depends on its parent node 15 The <offset size> depends on its parent node. It can be any memory-mapped
16 address. The size must be either 1, 2, or 4 16 address. The size must be either 1, 2, or 4 bytes. If reg is omitted, the
17 resource of this device will be used. 17 resource of this device will be used.
18 - little-endian: The existence indicates the r 18 - little-endian: The existence indicates the register is in little endian.
19 - big-endian: The existence indicates the regi 19 - big-endian: The existence indicates the register is in big endian.
20 If both little-endian and big-endian are omi 20 If both little-endian and big-endian are omitted, the endianness of the
21 CPU will be used. 21 CPU will be used.
22 - write-only: The existence indicates the regi 22 - write-only: The existence indicates the register is write-only.
23 - idle-state: value to set the muxer to when i 23 - idle-state: value to set the muxer to when idle. When no value is
24 given, it defaults to the last value used. 24 given, it defaults to the last value used.
25 25
26 Whenever an access is made to a device on a ch 26 Whenever an access is made to a device on a child bus, the value set
27 in the relevant node's reg property will be ou 27 in the relevant node's reg property will be output to the register.
28 28
29 If an idle state is defined, using the idle-st 29 If an idle state is defined, using the idle-state (optional) property,
30 whenever an access is not being made to a devi 30 whenever an access is not being made to a device on a child bus, the
31 register will be set according to the idle val 31 register will be set according to the idle value.
32 32
33 If an idle state is not defined, the most rece 33 If an idle state is not defined, the most recently used value will be
34 left programmed into the register. 34 left programmed into the register.
35 35
36 Example of a mux on PCIe card, the host is a p 36 Example of a mux on PCIe card, the host is a powerpc SoC (big endian):
37 37
38 i2c-mux { 38 i2c-mux {
39 /* the <offset size> depends o 39 /* the <offset size> depends on the address translation
40 * of the parent device. If om 40 * of the parent device. If omitted, device resource
41 * will be used instead. The s 41 * will be used instead. The size is to determine
42 * whether iowrite32, iowrite1 42 * whether iowrite32, iowrite16, or iowrite8 will be used.
43 */ 43 */
44 reg = <0x6028 0x4>; 44 reg = <0x6028 0x4>;
45 little-endian; /* lit 45 little-endian; /* little endian register on PCIe */
46 compatible = "i2c-mux-reg"; 46 compatible = "i2c-mux-reg";
47 #address-cells = <1>; 47 #address-cells = <1>;
48 #size-cells = <0>; 48 #size-cells = <0>;
49 i2c-parent = <&i2c1>; 49 i2c-parent = <&i2c1>;
50 i2c@0 { 50 i2c@0 {
51 reg = <0>; 51 reg = <0>;
52 #address-cells = <1>; 52 #address-cells = <1>;
53 #size-cells = <0>; 53 #size-cells = <0>;
54 54
55 si5338: clock-generato 55 si5338: clock-generator@70 {
56 compatible = " 56 compatible = "silabs,si5338";
57 reg = <0x70>; 57 reg = <0x70>;
58 /* other stuff 58 /* other stuff */
59 }; 59 };
60 }; 60 };
61 61
62 i2c@1 { 62 i2c@1 {
63 /* data is written usi 63 /* data is written using iowrite32 */
64 reg = <1>; 64 reg = <1>;
65 #address-cells = <1>; 65 #address-cells = <1>;
66 #size-cells = <0>; 66 #size-cells = <0>;
67 67
68 si5338: clock-generato 68 si5338: clock-generator@70 {
69 compatible = " 69 compatible = "silabs,si5338";
70 reg = <0x70>; 70 reg = <0x70>;
71 /* other stuff 71 /* other stuff */
72 }; 72 };
73 }; 73 };
74 }; 74 };
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