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diff --git a/Documentation/devicetree/bindings/display/mipi-dsi-bus.txt b/Documentation/devicetree/bindings/display/mipi-dsi-bus.txt new file mode 100644 index 000000000..a336599f6 --- /dev/null +++ b/Documentation/devicetree/bindings/display/mipi-dsi-bus.txt @@ -0,0 +1,235 @@ +MIPI DSI (Display Serial Interface) busses +========================================== + +The MIPI Display Serial Interface specifies a serial bus and a protocol for +communication between a host and up to four peripherals. This document will +define the syntax used to represent a DSI bus in a device tree. + +This document describes DSI bus-specific properties only or defines existing +standard properties in the context of the DSI bus. + +Each DSI host provides a DSI bus. The DSI host controller's node contains a +set of properties that characterize the bus. Child nodes describe individual +peripherals on that bus. + +The following assumes that only a single peripheral is connected to a DSI +host. Experience shows that this is true for the large majority of setups. + +DSI host +======== + +In addition to the standard properties and those defined by the parent bus of +a DSI host, the following properties apply to a node representing a DSI host. + +Required properties: +- #address-cells: The number of cells required to represent an address on the + bus. DSI peripherals are addressed using a 2-bit virtual channel number, so + a maximum of 4 devices can be addressed on a single bus. Hence the value of + this property should be 1. +- #size-cells: Should be 0. There are cases where it makes sense to use a + different value here. See below. + +Optional properties: +- clock-master: boolean. Should be enabled if the host is being used in + conjunction with another DSI host to drive the same peripheral. Hardware + supporting such a configuration generally requires the data on both the busses + to be driven by the same clock. Only the DSI host instance controlling this + clock should contain this property. + +DSI peripheral +============== + +Peripherals with DSI as control bus, or no control bus +------------------------------------------------------ + +Peripherals with the DSI bus as the primary control bus, or peripherals with +no control bus but use the DSI bus to transmit pixel data are represented +as child nodes of the DSI host's node. Properties described here apply to all +DSI peripherals, but individual bindings may want to define additional, +device-specific properties. + +Required properties: +- reg: The virtual channel number of a DSI peripheral. Must be in the range + from 0 to 3. + +Some DSI peripherals respond to more than a single virtual channel. In that +case two alternative representations can be chosen: +- The reg property can take multiple entries, one for each virtual channel + that the peripheral responds to. +- If the virtual channels that a peripheral responds to are consecutive, the + #size-cells can be set to 1. The first cell of each entry in the reg + property is the number of the first virtual channel and the second cell is + the number of consecutive virtual channels. + +Peripherals with a different control bus +---------------------------------------- + +There are peripherals that have I2C/SPI (or some other non-DSI bus) as the +primary control bus, but are also connected to a DSI bus (mostly for the data +path). Connections between such peripherals and a DSI host can be represented +using the graph bindings [1], [2]. + +Peripherals that support dual channel DSI +----------------------------------------- + +Peripherals with higher bandwidth requirements can be connected to 2 DSI +busses. Each DSI bus/channel drives some portion of the pixel data (generally +left/right half of each line of the display, or even/odd lines of the display). +The graph bindings should be used to represent the multiple DSI busses that are +connected to this peripheral. Each DSI host's output endpoint can be linked to +an input endpoint of the DSI peripheral. + +[1] Documentation/devicetree/bindings/graph.txt +[2] Documentation/devicetree/bindings/media/video-interfaces.txt + +Examples +======== +- (1), (2) and (3) are examples of a DSI host and peripheral on the DSI bus + with different virtual channel configurations. +- (4) is an example of a peripheral on a I2C control bus connected to a + DSI host using of-graph bindings. +- (5) is an example of 2 DSI hosts driving a dual-channel DSI peripheral, + which uses I2C as its primary control bus. + +1) + dsi-host { + ... + + #address-cells = <1>; + #size-cells = <0>; + + /* peripheral responds to virtual channel 0 */ + peripheral@0 { + compatible = "..."; + reg = <0>; + }; + + ... + }; + +2) + dsi-host { + ... + + #address-cells = <1>; + #size-cells = <0>; + + /* peripheral responds to virtual channels 0 and 2 */ + peripheral@0 { + compatible = "..."; + reg = <0, 2>; + }; + + ... + }; + +3) + dsi-host { + ... + + #address-cells = <1>; + #size-cells = <1>; + + /* peripheral responds to virtual channels 1, 2 and 3 */ + peripheral@1 { + compatible = "..."; + reg = <1 3>; + }; + + ... + }; + +4) + i2c-host { + ... + + dsi-bridge@35 { + compatible = "..."; + reg = <0x35>; + + ports { + ... + + port { + bridge_mipi_in: endpoint { + remote-endpoint = <&host_mipi_out>; + }; + }; + }; + }; + }; + + dsi-host { + ... + + ports { + ... + + port { + host_mipi_out: endpoint { + remote-endpoint = <&bridge_mipi_in>; + }; + }; + }; + }; + +5) + i2c-host { + dsi-bridge@35 { + compatible = "..."; + reg = <0x35>; + + ports { + #address-cells = <1>; + #size-cells = <0>; + + port@0 { + reg = <0>; + dsi0_in: endpoint { + remote-endpoint = <&dsi0_out>; + }; + }; + + port@1 { + reg = <1>; + dsi1_in: endpoint { + remote-endpoint = <&dsi1_out>; + }; + }; + }; + }; + }; + + dsi0-host { + ... + + /* + * this DSI instance drives the clock for both the host + * controllers + */ + clock-master; + + ports { + ... + + port { + dsi0_out: endpoint { + remote-endpoint = <&dsi0_in>; + }; + }; + }; + }; + + dsi1-host { + ... + + ports { + ... + + port { + dsi1_out: endpoint { + remote-endpoint = <&dsi1_in>; + }; + }; + }; + }; |