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Linux/Documentation/devicetree/bindings/media/video-interfaces.txt

  1 Common bindings for video receiver and transmitter interfaces
  2 
  3 General concept
  4 ---------------
  5 
  6 Video data pipelines usually consist of external devices, e.g. camera sensors,
  7 controlled over an I2C, SPI or UART bus, and SoC internal IP blocks, including
  8 video DMA engines and video data processors.
  9 
 10 SoC internal blocks are described by DT nodes, placed similarly to other SoC
 11 blocks.  External devices are represented as child nodes of their respective
 12 bus controller nodes, e.g. I2C.
 13 
 14 Data interfaces on all video devices are described by their child 'port' nodes.
 15 Configuration of a port depends on other devices participating in the data
 16 transfer and is described by 'endpoint' subnodes.
 17 
 18 device {
 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 
 33 If a port can be configured to work with more than one remote device on the same
 34 bus, an 'endpoint' child node must be provided for each of them.  If more than
 35 one port is present in a device node or there is more than one endpoint at a
 36 port, or port node needs to be associated with a selected hardware interface,
 37 a common scheme using '#address-cells', '#size-cells' and 'reg' properties is
 38 used.
 39 
 40 All 'port' nodes can be grouped under optional 'ports' node, which allows to
 41 specify #address-cells, #size-cells properties independently for the 'port'
 42 and 'endpoint' nodes and any child device nodes a device might have.
 43 
 44 Two 'endpoint' nodes are linked with each other through their 'remote-endpoint'
 45 phandles.  An endpoint subnode of a device contains all properties needed for
 46 configuration of this device for data exchange with other device.  In most
 47 cases properties at the peer 'endpoint' nodes will be identical, however they
 48 might need to be different when there is any signal modifications on the bus
 49 between two devices, e.g. there are logic signal inverters on the lines.
 50 
 51 It is allowed for multiple endpoints at a port to be active simultaneously,
 52 where supported by a device.  For example, in case where a data interface of
 53 a device is partitioned into multiple data busses, e.g. 16-bit input port
 54 divided into two separate ITU-R BT.656 8-bit busses.  In such case bus-width
 55 and data-shift properties can be used to assign physical data lines to each
 56 endpoint node (logical bus).
 57 
 58 
 59 Required properties
 60 -------------------
 61 
 62 If there is more than one 'port' or more than one 'endpoint' node or 'reg'
 63 property is present in port and/or endpoint nodes the following properties
 64 are 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 
 70 Optional 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 - sync-on-green-active: active state of Sync-on-green (SoG) signal, 0/1 for
 92   LOW/HIGH respectively.
 93 - data-lanes: an array of physical data lane indexes. Position of an entry
 94   determines the logical lane number, while the value of an entry indicates
 95   physical lane, e.g. for 2-lane MIPI CSI-2 bus we could have
 96   "data-lanes = <1 2>;", assuming the clock lane is on hardware lane 0.
 97   This property is valid for serial busses only (e.g. MIPI CSI-2).
 98 - clock-lanes: an array of physical clock lane indexes. Position of an entry
 99   determines the logical lane number, while the value of an entry indicates
100   physical lane, e.g. for a MIPI CSI-2 bus we could have "clock-lanes = <0>;",
101   which places the clock lane on hardware lane 0. This property is valid for
102   serial busses only (e.g. MIPI CSI-2). Note that for the MIPI CSI-2 bus this
103   array contains only one entry.
104 - clock-noncontinuous: a boolean property to allow MIPI CSI-2 non-continuous
105   clock mode.
106 
107 
108 Example
109 -------
110 
111 The example snippet below describes two data pipelines.  ov772x and imx074 are
112 camera sensors with a parallel and serial (MIPI CSI-2) video bus respectively.
113 Both sensors are on the I2C control bus corresponding to the i2c0 controller
114 node.  ov772x sensor is linked directly to the ceu0 video host interface.
115 imx074 is linked to ceu0 through the MIPI CSI-2 receiver (csi2). ceu0 has a
116 (single) DMA engine writing captured data to memory.  ceu0 node has a single
117 'port' node which may indicate that at any time only one of the following data
118 pipelines can be active: ov772x -> ceu0 or imx074 -> csi2 -> ceu0.
119 
120         ceu0: ceu@0xfe910000 {
121                 compatible = "renesas,sh-mobile-ceu";
122                 reg = <0xfe910000 0xa0>;
123                 interrupts = <0x880>;
124 
125                 mclk: master_clock {
126                         compatible = "renesas,ceu-clock";
127                         #clock-cells = <1>;
128                         clock-frequency = <50000000>;   /* Max clock frequency */
129                         clock-output-names = "mclk";
130                 };
131 
132                 port {
133                         #address-cells = <1>;
134                         #size-cells = <0>;
135 
136                         /* Parallel bus endpoint */
137                         ceu0_1: endpoint@1 {
138                                 reg = <1>;              /* Local endpoint # */
139                                 remote = <&ov772x_1_1>; /* Remote phandle */
140                                 bus-width = <8>;        /* Used data lines */
141                                 data-shift = <2>;       /* Lines 9:2 are used */
142 
143                                 /* If hsync-active/vsync-active are missing,
144                                    embedded BT.656 sync is used */
145                                 hsync-active = <0>;     /* Active low */
146                                 vsync-active = <0>;     /* Active low */
147                                 data-active = <1>;      /* Active high */
148                                 pclk-sample = <1>;      /* Rising */
149                         };
150 
151                         /* MIPI CSI-2 bus endpoint */
152                         ceu0_0: endpoint@0 {
153                                 reg = <0>;
154                                 remote = <&csi2_2>;
155                         };
156                 };
157         };
158 
159         i2c0: i2c@0xfff20000 {
160                 ...
161                 ov772x_1: camera@0x21 {
162                         compatible = "omnivision,ov772x";
163                         reg = <0x21>;
164                         vddio-supply = <&regulator1>;
165                         vddcore-supply = <&regulator2>;
166 
167                         clock-frequency = <20000000>;
168                         clocks = <&mclk 0>;
169                         clock-names = "xclk";
170 
171                         port {
172                                 /* With 1 endpoint per port no need for addresses. */
173                                 ov772x_1_1: endpoint {
174                                         bus-width = <8>;
175                                         remote-endpoint = <&ceu0_1>;
176                                         hsync-active = <1>;
177                                         vsync-active = <0>; /* Who came up with an
178                                                                inverter here ?... */
179                                         data-active = <1>;
180                                         pclk-sample = <1>;
181                                 };
182                         };
183                 };
184 
185                 imx074: camera@0x1a {
186                         compatible = "sony,imx074";
187                         reg = <0x1a>;
188                         vddio-supply = <&regulator1>;
189                         vddcore-supply = <&regulator2>;
190 
191                         clock-frequency = <30000000>;   /* Shared clock with ov772x_1 */
192                         clocks = <&mclk 0>;
193                         clock-names = "sysclk";         /* Assuming this is the
194                                                            name in the datasheet */
195                         port {
196                                 imx074_1: endpoint {
197                                         clock-lanes = <0>;
198                                         data-lanes = <1 2>;
199                                         remote-endpoint = <&csi2_1>;
200                                 };
201                         };
202                 };
203         };
204 
205         csi2: csi2@0xffc90000 {
206                 compatible = "renesas,sh-mobile-csi2";
207                 reg = <0xffc90000 0x1000>;
208                 interrupts = <0x17a0>;
209                 #address-cells = <1>;
210                 #size-cells = <0>;
211 
212                 port@1 {
213                         compatible = "renesas,csi2c";   /* One of CSI2I and CSI2C. */
214                         reg = <1>;                      /* CSI-2 PHY #1 of 2: PHY_S,
215                                                            PHY_M has port address 0,
216                                                            is unused. */
217                         csi2_1: endpoint {
218                                 clock-lanes = <0>;
219                                 data-lanes = <2 1>;
220                                 remote-endpoint = <&imx074_1>;
221                         };
222                 };
223                 port@2 {
224                         reg = <2>;                      /* port 2: link to the CEU */
225 
226                         csi2_2: endpoint {
227                                 remote-endpoint = <&ceu0_0>;
228                         };
229                 };
230         };

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