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1MIPI DSI (Display Serial Interface) busses2==========================================3 4The MIPI Display Serial Interface specifies a serial bus and a protocol for5communication between a host and up to four peripherals. This document will6define the syntax used to represent a DSI bus in a device tree.7 8This document describes DSI bus-specific properties only or defines existing9standard properties in the context of the DSI bus.10 11Each DSI host provides a DSI bus. The DSI host controller's node contains a12set of properties that characterize the bus. Child nodes describe individual13peripherals on that bus.14 15The following assumes that only a single peripheral is connected to a DSI16host. Experience shows that this is true for the large majority of setups.17 18DSI host19========20 21In addition to the standard properties and those defined by the parent bus of22a DSI host, the following properties apply to a node representing a DSI host.23 24Required properties:25- #address-cells: The number of cells required to represent an address on the26 bus. DSI peripherals are addressed using a 2-bit virtual channel number, so27 a maximum of 4 devices can be addressed on a single bus. Hence the value of28 this property should be 1.29- #size-cells: Should be 0. There are cases where it makes sense to use a30 different value here. See below.31 32Optional properties:33- clock-master: boolean. Should be enabled if the host is being used in34 conjunction with another DSI host to drive the same peripheral. Hardware35 supporting such a configuration generally requires the data on both the busses36 to be driven by the same clock. Only the DSI host instance controlling this37 clock should contain this property.38 39DSI peripheral40==============41 42Peripherals with DSI as control bus, or no control bus43------------------------------------------------------44 45Peripherals with the DSI bus as the primary control bus, or peripherals with46no control bus but use the DSI bus to transmit pixel data are represented47as child nodes of the DSI host's node. Properties described here apply to all48DSI peripherals, but individual bindings may want to define additional,49device-specific properties.50 51Required properties:52- reg: The virtual channel number of a DSI peripheral. Must be in the range53 from 0 to 3.54 55Some DSI peripherals respond to more than a single virtual channel. In that56case two alternative representations can be chosen:57- The reg property can take multiple entries, one for each virtual channel58 that the peripheral responds to.59- If the virtual channels that a peripheral responds to are consecutive, the60 #size-cells can be set to 1. The first cell of each entry in the reg61 property is the number of the first virtual channel and the second cell is62 the number of consecutive virtual channels.63 64Peripherals with a different control bus65----------------------------------------66 67There are peripherals that have I2C/SPI (or some other non-DSI bus) as the68primary control bus, but are also connected to a DSI bus (mostly for the data69path). Connections between such peripherals and a DSI host can be represented70using the graph bindings [1], [2].71 72Peripherals that support dual channel DSI73-----------------------------------------74 75Peripherals with higher bandwidth requirements can be connected to 2 DSI76busses. Each DSI bus/channel drives some portion of the pixel data (generally77left/right half of each line of the display, or even/odd lines of the display).78The graph bindings should be used to represent the multiple DSI busses that are79connected to this peripheral. Each DSI host's output endpoint can be linked to80an input endpoint of the DSI peripheral.81 82[1] Documentation/devicetree/bindings/graph.txt83[2] Documentation/devicetree/bindings/media/video-interfaces.txt84 85Examples86========87- (1), (2) and (3) are examples of a DSI host and peripheral on the DSI bus88 with different virtual channel configurations.89- (4) is an example of a peripheral on a I2C control bus connected to a90 DSI host using of-graph bindings.91- (5) is an example of 2 DSI hosts driving a dual-channel DSI peripheral,92 which uses I2C as its primary control bus.93 941)95 dsi-host {96 ...97 98 #address-cells = <1>;99 #size-cells = <0>;100 101 /* peripheral responds to virtual channel 0 */102 peripheral@0 {103 compatible = "...";104 reg = <0>;105 };106 107 ...108 };109 1102)111 dsi-host {112 ...113 114 #address-cells = <1>;115 #size-cells = <0>;116 117 /* peripheral responds to virtual channels 0 and 2 */118 peripheral@0 {119 compatible = "...";120 reg = <0, 2>;121 };122 123 ...124 };125 1263)127 dsi-host {128 ...129 130 #address-cells = <1>;131 #size-cells = <1>;132 133 /* peripheral responds to virtual channels 1, 2 and 3 */134 peripheral@1 {135 compatible = "...";136 reg = <1 3>;137 };138 139 ...140 };141 1424)143 i2c-host {144 ...145 146 dsi-bridge@35 {147 compatible = "...";148 reg = <0x35>;149 150 ports {151 ...152 153 port {154 bridge_mipi_in: endpoint {155 remote-endpoint = <&host_mipi_out>;156 };157 };158 };159 };160 };161 162 dsi-host {163 ...164 165 ports {166 ...167 168 port {169 host_mipi_out: endpoint {170 remote-endpoint = <&bridge_mipi_in>;171 };172 };173 };174 };175 1765)177 i2c-host {178 dsi-bridge@35 {179 compatible = "...";180 reg = <0x35>;181 182 ports {183 #address-cells = <1>;184 #size-cells = <0>;185 186 port@0 {187 reg = <0>;188 dsi0_in: endpoint {189 remote-endpoint = <&dsi0_out>;190 };191 };192 193 port@1 {194 reg = <1>;195 dsi1_in: endpoint {196 remote-endpoint = <&dsi1_out>;197 };198 };199 };200 };201 };202 203 dsi0-host {204 ...205 206 /*207 * this DSI instance drives the clock for both the host208 * controllers209 */210 clock-master;211 212 ports {213 ...214 215 port {216 dsi0_out: endpoint {217 remote-endpoint = <&dsi0_in>;218 };219 };220 };221 };222 223 dsi1-host {224 ...225 226 ports {227 ...228 229 port {230 dsi1_out: endpoint {231 remote-endpoint = <&dsi1_in>;232 };233 };234 };235 };236