[PATCH RFC v5 1/2] [media] Add common video interfaces OF bindings documentation
Sylwester Nawrocki
s.nawrocki at samsung.com
Fri Feb 1 04:18:57 EST 2013
From: Guennadi Liakhovetski <g.liakhovetski at gmx.de>
This patch adds a document describing common OF bindings for video
capture, output and video processing devices. It is curently mainly
focused on video capture devices, with data busses defined by
standards like ITU-R BT.656 or MIPI-CSI2.
It also documents a method of describing data links between devices.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski at gmx.de>
Signed-off-by: Sylwester Nawrocki <s.nawrocki at samsung.com>
---
Changes since v4:
- added note that multiple endpoints at a port can be active at any time,
- introduced optional 'ports' node aggregating 'port' nodes if required
to avoid conflicts with any child bus of a device,
- improved definition of the 'slave-mode' property,
- corrected 'bus-width' and 'data-shift' properties specification,
- dropped 'immutable' properties in the example dts snippet.
---
.../devicetree/bindings/media/video-interfaces.txt | 216 ++++++++++++++++++++
1 file changed, 216 insertions(+)
create mode 100644 Documentation/devicetree/bindings/media/video-interfaces.txt
diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt b/Documentation/devicetree/bindings/media/video-interfaces.txt
new file mode 100644
index 0000000..14c4be1
--- /dev/null
+++ b/Documentation/devicetree/bindings/media/video-interfaces.txt
@@ -0,0 +1,216 @@
+Common bindings for video data receiver and transmitter interfaces
+
+General concept
+---------------
+
+Video data pipelines usually consist of external devices, e.g. camera sensors,
+controlled over an I2C, SPI or UART bus, and SoC internal IP blocks, including
+video DMA engines and video data processors.
+
+SoC internal blocks are described by DT nodes, placed similarly to other SoC
+blocks. External devices are represented as child nodes of their respective
+bus controller nodes, e.g. I2C.
+
+Data interfaces on all video devices are described by their child 'port' nodes.
+Configuration of a port depends on other devices participating in the data
+transfer and is described by 'endpoint' subnodes.
+
+device {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ port at 0 {
+ endpoint at 0 { ... };
+ endpoint at 1 { ... };
+ };
+ port at 1 { ... };
+};
+
+If a port can be configured to work with more than one other device on the same
+bus, an 'endpoint' child node must be provided for each of them. If more than
+one port is present in a device node or there is more than one endpoint at a
+port, a common scheme, using '#address-cells', '#size-cells' and 'reg'
+properties is used.
+
+Two 'endpoint' nodes are linked with each other through their 'remote-endpoint'
+phandles. An endpoint subnode of a device contains all properties needed for
+configuration of this device for data exchange with the other device. In most
+cases properties at the peer 'endpoint' nodes will be identical, however
+they might need to be different when there is any signal modifications on the
+bus between two devices, e.g. there are logic signal inverters on the lines.
+
+It is allowed for multiple endpoints at a port to be active simultaneously,
+where supported by a device. For example in case where a data interface of
+a device is partitioned into multiple data busses, e.g. 16-bit input port
+divided into two separate ITU-R BT.656 8-bit busses. In such a case bus-width
+and data-shift properties can be used to assign physical data lines to each
+endpoint node (logical bus).
+
+Required properties
+-------------------
+
+If there is more than one 'port' or more than one 'endpoint' node or 'reg'
+property is present in port and/or endpoint nodes the following properties
+are required in relevant parent node:
+
+ - #address-cells : number of cells required to define port/endpoint
+ identifier, should be 1.
+ - #size-cells : should be zero.
+
+Optional endpoint properties
+----------------------------
+
+- remote-endpoint: phandle to an 'endpoint' subnode of the other device node.
+- slave-mode: a boolean property indicating that the link is run in slave mode.
+ The default when this property is not specified is master mode. In the slave
+ mode horizontal and vertical synchronization signals are provided to the
+ slave device (data source) by the master device (data sink). In the master
+ mode the data source device is also the source of the synchronization signals.
+- bus-width: number of data lines actively used, valid for the parallel busses.
+- data-shift: on the parallel data busses, if bus-width is used to specify the
+ number of data lines, data-shift can be used to specify which data lines are
+ used, e.g. "bus-width=<8>; data-shift=<2>;" means, that lines 9:2 are used.
+- hsync-active: active state of HSYNC signal, 0/1 for LOW/HIGH respectively.
+- vsync-active: active state of VSYNC signal, 0/1 for LOW/HIGH respectively.
+ Note, that if HSYNC and VSYNC polarities are not specified, embedded
+ synchronization may be required, where supported.
+- data-active: similar to HSYNC and VSYNC, specifies data line polarity.
+- field-even-active: field signal level during the even field data transmission.
+- pclk-sample: sample data on rising (1) or falling (0) edge of the pixel clock
+ signal.
+- data-lanes: an array of physical data lane indexes. Position of an entry
+ determines the logical lane number, while the value of an entry indicates
+ physical lane, e.g. for 2-lane MIPI CSI-2 bus we could have
+ "data-lanes = <1 2>;", assuming the clock lane is on hardware lane 0.
+ This property is valid for serial busses only (e.g. MIPI CSI-2).
+- clock-lanes: an array of physical clock lane indexes. Position of an entry
+ determines the logical lane number, while the value of an entry indicates
+ physical lane, e.g. for a MIPI CSI-2 bus we could have "clock-lanes = <0>;",
+ which places the clock lane on hardware lane 0. This property is valid for
+ serial busses only (e.g. MIPI CSI-2). Note that for the MIPI CSI-2 bus this
+ array contains only one entry.
+- clock-noncontinuous: a boolean property to allow MIPI CSI-2 non-continuous
+ clock mode.
+
+Example
+-------
+
+The example snippet below describes two data pipelines. ov772x and imx074 are
+camera sensors with a parallel and serial (MIPI CSI-2) video bus respectively.
+Both sensors are on the I2C control bus corresponding to the i2c0 controller
+node. ov772x sensor is linked directly to the ceu0 video host interface.
+imx074 is linked to ceu0 through the MIPI CSI-2 receiver (csi2). ceu0 has a
+(single) DMA engine writing captured data to memory. ceu0 node has a single
+'port' node which may indicate that at any time only one of the following data
+pipelines can be active: ov772x -> ceu0 or imx074 -> csi2 -> ceu0.
+
+ ceu0: ceu at 0xfe910000 {
+ compatible = "renesas,sh-mobile-ceu";
+ reg = <0xfe910000 0xa0>;
+ interrupts = <0x880>;
+
+ mclk: master_clock {
+ compatible = "renesas,ceu-clock";
+ #clock-cells = <1>;
+ clock-frequency = <50000000>; /* Max clock frequency */
+ clock-output-names = "mclk";
+ };
+
+ port {
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ /* Parallel bus endpoint */
+ ceu0_1: endpoint at 1 {
+ reg = <1>; /* Local endpoint # */
+ remote = <&ov772x_1_1>; /* Remote phandle */
+ bus-width = <8>; /* Used data lines */
+ data-shift = <2>; /* Lines 9:2 are used */
+
+ /* If hsync-active/vsync-active are missing,
+ embedded BT.656 sync is used */
+ hsync-active = <0>; /* Active low */
+ vsync-active = <0>; /* Active low */
+ data-active = <1>; /* Active high */
+ pclk-sample = <1>; /* Rising */
+ };
+
+ /* MIPI CSI-2 bus endpoint */
+ ceu0_0: endpoint at 0 {
+ reg = <0>;
+ remote = <&csi2_2>;
+ };
+ };
+ };
+
+ i2c0: i2c at 0xfff20000 {
+ ...
+ ov772x_1: camera at 0x21 {
+ compatible = "omnivision,ov772x";
+ reg = <0x21>;
+ vddio-supply = <®ulator1>;
+ vddcore-supply = <®ulator2>;
+
+ clock-frequency = <20000000>;
+ clocks = <&mclk 0>;
+ clock-names = "xclk";
+
+ port {
+ /* With 1 endpoint per port no need for addresses. */
+ ov772x_1_1: endpoint {
+ bus-width = <8>;
+ remote-endpoint = <&ceu0_1>;
+ hsync-active = <1>;
+ vsync-active = <0>; /* Who came up with an
+ inverter here ?... */
+ data-active = <1>;
+ pclk-sample = <1>;
+ };
+ };
+ };
+
+ imx074: camera at 0x1a {
+ compatible = "sony,imx074";
+ reg = <0x1a>;
+ vddio-supply = <®ulator1>;
+ vddcore-supply = <®ulator2>;
+
+ clock-frequency = <30000000>; /* Shared clock with ov772x_1 */
+ clocks = <&mclk 0>;
+ clock-names = "sysclk"; /* Assuming this is the
+ name in the datasheet */
+ port {
+ imx074_1: endpoint {
+ clock-lanes = <0>;
+ data-lanes = <1 2>;
+ remote-endpoint = <&csi2_1>;
+ };
+ };
+ };
+ };
+
+ csi2: csi2 at 0xffc90000 {
+ compatible = "renesas,sh-mobile-csi2";
+ reg = <0xffc90000 0x1000>;
+ interrupts = <0x17a0>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ port at 1 {
+ compatible = "renesas,csi2c"; /* One of CSI2I and CSI2C. */
+ reg = <1>; /* CSI-2 PHY #1 of 2: PHY_S,
+ PHY_M has port address 0,
+ is unused. */
+ csi2_1: endpoint {
+ clock-lanes = <0>;
+ data-lanes = <2 1>;
+ remote-endpoint = <&imx074_1>;
+ };
+ };
+ port at 2 {
+ reg = <2>; /* port 2: link to the CEU */
+
+ csi2_2: endpoint {
+ remote-endpoint = <&ceu0_0>;
+ };
+ };
+ };
--
1.7.9.5
More information about the devicetree-discuss
mailing list