linux/Documentation/devicetree/bindings/media/video-interfaces.txt
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   1Common bindings for video receiver and transmitter interfaces
   2
   3General concept
   4---------------
   5
   6Video data pipelines usually consist of external devices, e.g. camera sensors,
   7controlled over an I2C, SPI or UART bus, and SoC internal IP blocks, including
   8video DMA engines and video data processors.
   9
  10SoC internal blocks are described by DT nodes, placed similarly to other SoC
  11blocks.  External devices are represented as child nodes of their respective
  12bus controller nodes, e.g. I2C.
  13
  14Data interfaces on all video devices are described by their child 'port' nodes.
  15Configuration of a port depends on other devices participating in the data
  16transfer and is described by 'endpoint' subnodes.
  17
  18device {
  19        ...
  20        ports {
  21                #address-cells = <1>;
  22                #size-cells = <0>;
  23
  24                port@0 {
  25                        ...
  26                        endpoint@0 { ... };
  27                        endpoint@1 { ... };
  28                };
  29                port@1 { ... };
  30        };
  31};
  32
  33If a port can be configured to work with more than one remote device on the same
  34bus, an 'endpoint' child node must be provided for each of them.  If more than
  35one port is present in a device node or there is more than one endpoint at a
  36port, or port node needs to be associated with a selected hardware interface,
  37a common scheme using '#address-cells', '#size-cells' and 'reg' properties is
  38used.
  39
  40All 'port' nodes can be grouped under optional 'ports' node, which allows to
  41specify #address-cells, #size-cells properties independently for the 'port'
  42and 'endpoint' nodes and any child device nodes a device might have.
  43
  44Two 'endpoint' nodes are linked with each other through their 'remote-endpoint'
  45phandles.  An endpoint subnode of a device contains all properties needed for
  46configuration of this device for data exchange with other device.  In most
  47cases properties at the peer 'endpoint' nodes will be identical, however they
  48might need to be different when there is any signal modifications on the bus
  49between two devices, e.g. there are logic signal inverters on the lines.
  50
  51It is allowed for multiple endpoints at a port to be active simultaneously,
  52where supported by a device.  For example, in case where a data interface of
  53a device is partitioned into multiple data busses, e.g. 16-bit input port
  54divided into two separate ITU-R BT.656 8-bit busses.  In such case bus-width
  55and data-shift properties can be used to assign physical data lines to each
  56endpoint node (logical bus).
  57
  58
  59Required properties
  60-------------------
  61
  62If there is more than one 'port' or more than one 'endpoint' node or 'reg'
  63property is present in port and/or endpoint nodes the following properties
  64are required in a relevant parent node:
  65
  66 - #address-cells : number of cells required to define port/endpoint
  67                    identifier, should be 1.
  68 - #size-cells    : should be zero.
  69
  70Optional endpoint properties
  71----------------------------
  72
  73- remote-endpoint: phandle to an 'endpoint' subnode of a remote device node.
  74- slave-mode: a boolean property indicating that the link is run in slave mode.
  75  The default when this property is not specified is master mode. In the slave
  76  mode horizontal and vertical synchronization signals are provided to the
  77  slave device (data source) by the master device (data sink). In the master
  78  mode the data source device is also the source of the synchronization signals.
  79- bus-width: number of data lines actively used, valid for the parallel busses.
  80- data-shift: on the parallel data busses, if bus-width is used to specify the
  81  number of data lines, data-shift can be used to specify which data lines are
  82  used, e.g. "bus-width=<8>; data-shift=<2>;" means, that lines 9:2 are used.
  83- hsync-active: active state of the HSYNC signal, 0/1 for LOW/HIGH respectively.
  84- vsync-active: active state of the VSYNC signal, 0/1 for LOW/HIGH respectively.
  85  Note, that if HSYNC and VSYNC polarities are not specified, embedded
  86  synchronization may be required, where supported.
  87- data-active: similar to HSYNC and VSYNC, specifies data line polarity.
  88- field-even-active: field signal level during the even field data transmission.
  89- pclk-sample: sample data on rising (1) or falling (0) edge of the pixel clock
  90  signal.
  91- data-lanes: an array of physical data lane indexes. Position of an entry
  92  determines the logical lane number, while the value of an entry indicates
  93  physical lane, e.g. for 2-lane MIPI CSI-2 bus we could have
  94  "data-lanes = <1 2>;", assuming the clock lane is on hardware lane 0.
  95  This property is valid for serial busses only (e.g. MIPI CSI-2).
  96- clock-lanes: an array of physical clock lane indexes. Position of an entry
  97  determines the logical lane number, while the value of an entry indicates
  98  physical lane, e.g. for a MIPI CSI-2 bus we could have "clock-lanes = <0>;",
  99  which places the clock lane on hardware lane 0. This property is valid for
 100  serial busses only (e.g. MIPI CSI-2). Note that for the MIPI CSI-2 bus this
 101  array contains only one entry.
 102- clock-noncontinuous: a boolean property to allow MIPI CSI-2 non-continuous
 103  clock mode.
 104
 105
 106Example
 107-------
 108
 109The example snippet below describes two data pipelines.  ov772x and imx074 are
 110camera sensors with a parallel and serial (MIPI CSI-2) video bus respectively.
 111Both sensors are on the I2C control bus corresponding to the i2c0 controller
 112node.  ov772x sensor is linked directly to the ceu0 video host interface.
 113imx074 is linked to ceu0 through the MIPI CSI-2 receiver (csi2). ceu0 has a
 114(single) DMA engine writing captured data to memory.  ceu0 node has a single
 115'port' node which may indicate that at any time only one of the following data
 116pipelines can be active: ov772x -> ceu0 or imx074 -> csi2 -> ceu0.
 117
 118        ceu0: ceu@0xfe910000 {
 119                compatible = "renesas,sh-mobile-ceu";
 120                reg = <0xfe910000 0xa0>;
 121                interrupts = <0x880>;
 122
 123                mclk: master_clock {
 124                        compatible = "renesas,ceu-clock";
 125                        #clock-cells = <1>;
 126                        clock-frequency = <50000000>;   /* Max clock frequency */
 127                        clock-output-names = "mclk";
 128                };
 129
 130                port {
 131                        #address-cells = <1>;
 132                        #size-cells = <0>;
 133
 134                        /* Parallel bus endpoint */
 135                        ceu0_1: endpoint@1 {
 136                                reg = <1>;              /* Local endpoint # */
 137                                remote = <&ov772x_1_1>; /* Remote phandle */
 138                                bus-width = <8>;        /* Used data lines */
 139                                data-shift = <2>;       /* Lines 9:2 are used */
 140
 141                                /* If hsync-active/vsync-active are missing,
 142                                   embedded BT.656 sync is used */
 143                                hsync-active = <0>;     /* Active low */
 144                                vsync-active = <0>;     /* Active low */
 145                                data-active = <1>;      /* Active high */
 146                                pclk-sample = <1>;      /* Rising */
 147                        };
 148
 149                        /* MIPI CSI-2 bus endpoint */
 150                        ceu0_0: endpoint@0 {
 151                                reg = <0>;
 152                                remote = <&csi2_2>;
 153                        };
 154                };
 155        };
 156
 157        i2c0: i2c@0xfff20000 {
 158                ...
 159                ov772x_1: camera@0x21 {
 160                        compatible = "omnivision,ov772x";
 161                        reg = <0x21>;
 162                        vddio-supply = <&regulator1>;
 163                        vddcore-supply = <&regulator2>;
 164
 165                        clock-frequency = <20000000>;
 166                        clocks = <&mclk 0>;
 167                        clock-names = "xclk";
 168
 169                        port {
 170                                /* With 1 endpoint per port no need for addresses. */
 171                                ov772x_1_1: endpoint {
 172                                        bus-width = <8>;
 173                                        remote-endpoint = <&ceu0_1>;
 174                                        hsync-active = <1>;
 175                                        vsync-active = <0>; /* Who came up with an
 176                                                               inverter here ?... */
 177                                        data-active = <1>;
 178                                        pclk-sample = <1>;
 179                                };
 180                        };
 181                };
 182
 183                imx074: camera@0x1a {
 184                        compatible = "sony,imx074";
 185                        reg = <0x1a>;
 186                        vddio-supply = <&regulator1>;
 187                        vddcore-supply = <&regulator2>;
 188
 189                        clock-frequency = <30000000>;   /* Shared clock with ov772x_1 */
 190                        clocks = <&mclk 0>;
 191                        clock-names = "sysclk";         /* Assuming this is the
 192                                                           name in the datasheet */
 193                        port {
 194                                imx074_1: endpoint {
 195                                        clock-lanes = <0>;
 196                                        data-lanes = <1 2>;
 197                                        remote-endpoint = <&csi2_1>;
 198                                };
 199                        };
 200                };
 201        };
 202
 203        csi2: csi2@0xffc90000 {
 204                compatible = "renesas,sh-mobile-csi2";
 205                reg = <0xffc90000 0x1000>;
 206                interrupts = <0x17a0>;
 207                #address-cells = <1>;
 208                #size-cells = <0>;
 209
 210                port@1 {
 211                        compatible = "renesas,csi2c";   /* One of CSI2I and CSI2C. */
 212                        reg = <1>;                      /* CSI-2 PHY #1 of 2: PHY_S,
 213                                                           PHY_M has port address 0,
 214                                                           is unused. */
 215                        csi2_1: endpoint {
 216                                clock-lanes = <0>;
 217                                data-lanes = <2 1>;
 218                                remote-endpoint = <&imx074_1>;
 219                        };
 220                };
 221                port@2 {
 222                        reg = <2>;                      /* port 2: link to the CEU */
 223
 224                        csi2_2: endpoint {
 225                                remote-endpoint = <&ceu0_0>;
 226                        };
 227                };
 228        };
 229