[PATCH RFC v6] [media] Add common video interfaces OF bindings documentation

[Sylwester Nawrocki]

On 01/31/2013 07:41 PM, Sylwester Nawrocki wrote:
> 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 v5:
>  - added 'ports' node documentation

Hi Rob, Grant,

there was no more comments on this patch for a relatively long time
now. Would you apply it to your tree or could I send it for inclusion
in the media tree with your Ack ?

This version is different from the previous one that had your Ack
only in that there is now an optional 'ports' node aggregating all
'port' nodes of a device.

Thanks,
Sylwester

> ---
>  .../devicetree/bindings/media/video-interfaces.txt |  227 ++++++++++++++++++++
>  1 file changed, 227 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..278b17a
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/video-interfaces.txt
> @@ -0,1 +1,227 @@
> +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 {
> +	...
> +	ports {
> +		#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 remote 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, or port node needs to be associated with a specific hardware interface,
> +a common scheme using '#address-cells', '#size-cells' and 'reg' properties is
> +used.
> +
> +All 'port' nodes can be grouped under optional 'ports' node, which allows to
> +specify #address-cells, #size-cells properties independently for the 'port'
> +and 'endpoint' nodes and any children device nodes the device might have.
> +
> +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 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 = <&regulator1>;
> +			vddcore-supply = <&regulator2>;
> +
> +			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 = <&regulator1>;
> +			vddcore-supply = <&regulator2>;
> +
> +			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