1 MIPI DSI (Display Serial Interface) busses 1 MIPI DSI (Display Serial Interface) busses
2 ========================================== 2 ==========================================
3 3
4 The MIPI Display Serial Interface specifies a 4 The MIPI Display Serial Interface specifies a serial bus and a protocol for
5 communication between a host and up to four pe 5 communication between a host and up to four peripherals. This document will
6 define the syntax used to represent a DSI bus 6 define the syntax used to represent a DSI bus in a device tree.
7 7
8 This document describes DSI bus-specific prope 8 This document describes DSI bus-specific properties only or defines existing
9 standard properties in the context of the DSI 9 standard properties in the context of the DSI bus.
10 10
11 Each DSI host provides a DSI bus. The DSI host 11 Each DSI host provides a DSI bus. The DSI host controller's node contains a
12 set of properties that characterize the bus. C 12 set of properties that characterize the bus. Child nodes describe individual
13 peripherals on that bus. 13 peripherals on that bus.
14 14
15 The following assumes that only a single perip 15 The following assumes that only a single peripheral is connected to a DSI
16 host. Experience shows that this is true for t 16 host. Experience shows that this is true for the large majority of setups.
17 17
18 DSI host 18 DSI host
19 ======== 19 ========
20 20
21 In addition to the standard properties and tho 21 In addition to the standard properties and those defined by the parent bus of
22 a DSI host, the following properties apply to 22 a DSI host, the following properties apply to a node representing a DSI host.
23 23
24 Required properties: 24 Required properties:
25 - #address-cells: The number of cells required 25 - #address-cells: The number of cells required to represent an address on the
26 bus. DSI peripherals are addressed using a 2 26 bus. DSI peripherals are addressed using a 2-bit virtual channel number, so
27 a maximum of 4 devices can be addressed on a 27 a maximum of 4 devices can be addressed on a single bus. Hence the value of
28 this property should be 1. 28 this property should be 1.
29 - #size-cells: Should be 0. There are cases wh 29 - #size-cells: Should be 0. There are cases where it makes sense to use a
30 different value here. See below. 30 different value here. See below.
31 31
32 Optional properties: 32 Optional properties:
33 - clock-master: boolean. Should be enabled if 33 - clock-master: boolean. Should be enabled if the host is being used in
34 conjunction with another DSI host to drive t 34 conjunction with another DSI host to drive the same peripheral. Hardware
35 supporting such a configuration generally re 35 supporting such a configuration generally requires the data on both the busses
36 to be driven by the same clock. Only the DSI 36 to be driven by the same clock. Only the DSI host instance controlling this
37 clock should contain this property. 37 clock should contain this property.
38 38
39 DSI peripheral 39 DSI peripheral
40 ============== 40 ==============
41 41
42 Peripherals with DSI as control bus, or no con 42 Peripherals with DSI as control bus, or no control bus
43 ---------------------------------------------- 43 ------------------------------------------------------
44 44
45 Peripherals with the DSI bus as the primary co 45 Peripherals with the DSI bus as the primary control bus, or peripherals with
46 no control bus but use the DSI bus to transmit 46 no control bus but use the DSI bus to transmit pixel data are represented
47 as child nodes of the DSI host's node. Propert 47 as child nodes of the DSI host's node. Properties described here apply to all
48 DSI peripherals, but individual bindings may w 48 DSI peripherals, but individual bindings may want to define additional,
49 device-specific properties. 49 device-specific properties.
50 50
51 Required properties: 51 Required properties:
52 - reg: The virtual channel number of a DSI per 52 - reg: The virtual channel number of a DSI peripheral. Must be in the range
53 from 0 to 3. 53 from 0 to 3.
54 54
55 Some DSI peripherals respond to more than a si 55 Some DSI peripherals respond to more than a single virtual channel. In that
56 case two alternative representations can be ch 56 case two alternative representations can be chosen:
57 - The reg property can take multiple entries, 57 - The reg property can take multiple entries, one for each virtual channel
58 that the peripheral responds to. 58 that the peripheral responds to.
59 - If the virtual channels that a peripheral re 59 - If the virtual channels that a peripheral responds to are consecutive, the
60 #size-cells can be set to 1. The first cell 60 #size-cells can be set to 1. The first cell of each entry in the reg
61 property is the number of the first virtual 61 property is the number of the first virtual channel and the second cell is
62 the number of consecutive virtual channels. 62 the number of consecutive virtual channels.
63 63
64 Peripherals with a different control bus 64 Peripherals with a different control bus
65 ---------------------------------------- 65 ----------------------------------------
66 66
67 There are peripherals that have I2C/SPI (or so 67 There are peripherals that have I2C/SPI (or some other non-DSI bus) as the
68 primary control bus, but are also connected to 68 primary control bus, but are also connected to a DSI bus (mostly for the data
69 path). Connections between such peripherals an 69 path). Connections between such peripherals and a DSI host can be represented
70 using the graph bindings [1], [2]. 70 using the graph bindings [1], [2].
71 71
72 Peripherals that support dual channel DSI 72 Peripherals that support dual channel DSI
73 ----------------------------------------- 73 -----------------------------------------
74 74
75 Peripherals with higher bandwidth requirements 75 Peripherals with higher bandwidth requirements can be connected to 2 DSI
76 busses. Each DSI bus/channel drives some porti 76 busses. Each DSI bus/channel drives some portion of the pixel data (generally
77 left/right half of each line of the display, o 77 left/right half of each line of the display, or even/odd lines of the display).
78 The graph bindings should be used to represent 78 The graph bindings should be used to represent the multiple DSI busses that are
79 connected to this peripheral. Each DSI host's 79 connected to this peripheral. Each DSI host's output endpoint can be linked to
80 an input endpoint of the DSI peripheral. 80 an input endpoint of the DSI peripheral.
81 81
82 [1] Documentation/devicetree/bindings/graph.tx 82 [1] Documentation/devicetree/bindings/graph.txt
83 [2] Documentation/devicetree/bindings/media/vi 83 [2] Documentation/devicetree/bindings/media/video-interfaces.txt
84 84
85 Examples 85 Examples
86 ======== 86 ========
87 - (1), (2) and (3) are examples of a DSI host 87 - (1), (2) and (3) are examples of a DSI host and peripheral on the DSI bus
88 with different virtual channel configuration 88 with different virtual channel configurations.
89 - (4) is an example of a peripheral on a I2C c 89 - (4) is an example of a peripheral on a I2C control bus connected to a
90 DSI host using of-graph bindings. 90 DSI host using of-graph bindings.
91 - (5) is an example of 2 DSI hosts driving a d 91 - (5) is an example of 2 DSI hosts driving a dual-channel DSI peripheral,
92 which uses I2C as its primary control bus. 92 which uses I2C as its primary control bus.
93 93
94 1) 94 1)
95 dsi-host { 95 dsi-host {
96 ... 96 ...
97 97
98 #address-cells = <1>; 98 #address-cells = <1>;
99 #size-cells = <0>; 99 #size-cells = <0>;
100 100
101 /* peripheral responds to virt 101 /* peripheral responds to virtual channel 0 */
102 peripheral@0 { 102 peripheral@0 {
103 compatible = "..."; 103 compatible = "...";
104 reg = <0>; 104 reg = <0>;
105 }; 105 };
106 106
107 ... 107 ...
108 }; 108 };
109 109
110 2) 110 2)
111 dsi-host { 111 dsi-host {
112 ... 112 ...
113 113
114 #address-cells = <1>; 114 #address-cells = <1>;
115 #size-cells = <0>; 115 #size-cells = <0>;
116 116
117 /* peripheral responds to virt 117 /* peripheral responds to virtual channels 0 and 2 */
118 peripheral@0 { 118 peripheral@0 {
119 compatible = "..."; 119 compatible = "...";
120 reg = <0, 2>; 120 reg = <0, 2>;
121 }; 121 };
122 122
123 ... 123 ...
124 }; 124 };
125 125
126 3) 126 3)
127 dsi-host { 127 dsi-host {
128 ... 128 ...
129 129
130 #address-cells = <1>; 130 #address-cells = <1>;
131 #size-cells = <1>; 131 #size-cells = <1>;
132 132
133 /* peripheral responds to virt 133 /* peripheral responds to virtual channels 1, 2 and 3 */
134 peripheral@1 { 134 peripheral@1 {
135 compatible = "..."; 135 compatible = "...";
136 reg = <1 3>; 136 reg = <1 3>;
137 }; 137 };
138 138
139 ... 139 ...
140 }; 140 };
141 141
142 4) 142 4)
143 i2c-host { 143 i2c-host {
144 ... 144 ...
145 145
146 dsi-bridge@35 { 146 dsi-bridge@35 {
147 compatible = "..."; 147 compatible = "...";
148 reg = <0x35>; 148 reg = <0x35>;
149 149
150 ports { 150 ports {
151 ... 151 ...
152 152
153 port { 153 port {
154 bridge 154 bridge_mipi_in: endpoint {
155 155 remote-endpoint = <&host_mipi_out>;
156 }; 156 };
157 }; 157 };
158 }; 158 };
159 }; 159 };
160 }; 160 };
161 161
162 dsi-host { 162 dsi-host {
163 ... 163 ...
164 164
165 ports { 165 ports {
166 ... 166 ...
167 167
168 port { 168 port {
169 host_mipi_out: 169 host_mipi_out: endpoint {
170 remote 170 remote-endpoint = <&bridge_mipi_in>;
171 }; 171 };
172 }; 172 };
173 }; 173 };
174 }; 174 };
175 175
176 5) 176 5)
177 i2c-host { 177 i2c-host {
178 dsi-bridge@35 { 178 dsi-bridge@35 {
179 compatible = "..."; 179 compatible = "...";
180 reg = <0x35>; 180 reg = <0x35>;
181 181
182 ports { 182 ports {
183 #address-cells 183 #address-cells = <1>;
184 #size-cells = 184 #size-cells = <0>;
185 185
186 port@0 { 186 port@0 {
187 reg = 187 reg = <0>;
188 dsi0_i 188 dsi0_in: endpoint {
189 189 remote-endpoint = <&dsi0_out>;
190 }; 190 };
191 }; 191 };
192 192
193 port@1 { 193 port@1 {
194 reg = 194 reg = <1>;
195 dsi1_i 195 dsi1_in: endpoint {
196 196 remote-endpoint = <&dsi1_out>;
197 }; 197 };
198 }; 198 };
199 }; 199 };
200 }; 200 };
201 }; 201 };
202 202
203 dsi0-host { 203 dsi0-host {
204 ... 204 ...
205 205
206 /* 206 /*
207 * this DSI instance drives th 207 * this DSI instance drives the clock for both the host
208 * controllers 208 * controllers
209 */ 209 */
210 clock-master; 210 clock-master;
211 211
212 ports { 212 ports {
213 ... 213 ...
214 214
215 port { 215 port {
216 dsi0_out: endp 216 dsi0_out: endpoint {
217 remote 217 remote-endpoint = <&dsi0_in>;
218 }; 218 };
219 }; 219 };
220 }; 220 };
221 }; 221 };
222 222
223 dsi1-host { 223 dsi1-host {
224 ... 224 ...
225 225
226 ports { 226 ports {
227 ... 227 ...
228 228
229 port { 229 port {
230 dsi1_out: endp 230 dsi1_out: endpoint {
231 remote 231 remote-endpoint = <&dsi1_in>;
232 }; 232 };
233 }; 233 };
234 }; 234 };
235 }; 235 };
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