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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
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treea94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/devicetree/bindings/media/video-interfaces.txt
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+Common bindings for video 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@0 {
+ ...
+ endpoint@0 { ... };
+ endpoint@1 { ... };
+ };
+ port@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 selected 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 child device nodes a 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 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).
+
+Documenting bindings for devices
+--------------------------------
+
+All required and optional bindings the device supports shall be explicitly
+documented in device DT binding documentation. This also includes port and
+endpoint nodes for the device, including unit-addresses and reg properties where
+relevant.
+
+Please also see Documentation/devicetree/bindings/graph.txt .
+
+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 a relevant parent node:
+
+ - #address-cells : number of cells required to define port/endpoint
+ identifier, should be 1.
+ - #size-cells : should be zero.
+
+
+Optional properties
+-------------------
+
+- flash-leds: An array of phandles, each referring to a flash LED, a sub-node
+ of the LED driver device node.
+
+- lens-focus: A phandle to the node of the focus lens controller.
+
+- rotation: The camera rotation is expressed as the angular difference in
+ degrees between two reference systems, one relative to the camera module, and
+ one defined on the external world scene to be captured when projected on the
+ image sensor pixel array.
+
+ A camera sensor has a 2-dimensional reference system 'Rc' defined by
+ its pixel array read-out order. The origin is set to the first pixel
+ being read out, the X-axis points along the column read-out direction
+ towards the last columns, and the Y-axis along the row read-out
+ direction towards the last row.
+
+ A typical example for a sensor with a 2592x1944 pixel array matrix
+ observed from the front is:
+
+ 2591 X-axis 0
+ <------------------------+ 0
+ .......... ... ..........!
+ .......... ... ..........! Y-axis
+ ... !
+ .......... ... ..........!
+ .......... ... ..........! 1943
+ V
+
+ The external world scene reference system 'Rs' is a 2-dimensional
+ reference system on the focal plane of the camera module. The origin is
+ placed on the top-left corner of the visible scene, the X-axis points
+ towards the right, and the Y-axis points towards the bottom of the
+ scene. The top, bottom, left and right directions are intentionally not
+ defined and depend on the environment in which the camera is used.
+
+ A typical example of a (very common) picture of a shark swimming from
+ left to right, as seen from the camera, is:
+
+ 0 X-axis
+ 0 +------------------------------------->
+ !
+ !
+ !
+ ! |\____)\___
+ ! ) _____ __`<
+ ! |/ )/
+ !
+ !
+ !
+ V
+ Y-axis
+
+ with the reference system 'Rs' placed on the camera focal plane:
+
+ ¸.·˙!
+ ¸.·˙ !
+ _ ¸.·˙ !
+ +-/ \-+¸.·˙ !
+ | (o) | ! Camera focal plane
+ +-----+˙·.¸ !
+ ˙·.¸ !
+ ˙·.¸ !
+ ˙·.¸!
+
+ When projected on the sensor's pixel array, the image and the associated
+ reference system 'Rs' are typically (but not always) inverted, due to
+ the camera module's lens optical inversion effect.
+
+ Assuming the above represented scene of the swimming shark, the lens
+ inversion projects the scene and its reference system onto the sensor
+ pixel array, seen from the front of the camera sensor, as follows:
+
+ Y-axis
+ ^
+ !
+ !
+ !
+ ! |\_____)\__
+ ! ) ____ ___.<
+ ! |/ )/
+ !
+ !
+ !
+ 0 +------------------------------------->
+ 0 X-axis
+
+ Note the shark being upside-down.
+
+ The resulting projected reference system is named 'Rp'.
+
+ The camera rotation property is then defined as the angular difference
+ in the counter-clockwise direction between the camera reference system
+ 'Rc' and the projected scene reference system 'Rp'. It is expressed in
+ degrees as a number in the range [0, 360[.
+
+ Examples
+
+ 0 degrees camera rotation:
+
+
+ Y-Rp
+ ^
+ Y-Rc !
+ ^ !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! 0 +------------------------------------->
+ ! 0 X-Rp
+ 0 +------------------------------------->
+ 0 X-Rc
+
+
+ X-Rc 0
+ <------------------------------------+ 0
+ X-Rp 0 !
+ <------------------------------------+ 0 !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! V
+ ! Y-Rc
+ V
+ Y-Rp
+
+ 90 degrees camera rotation:
+
+ 0 Y-Rc
+ 0 +-------------------->
+ ! Y-Rp
+ ! ^
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! 0 +------------------------------------->
+ ! 0 X-Rp
+ !
+ !
+ !
+ !
+ V
+ X-Rc
+
+ 180 degrees camera rotation:
+
+ 0
+ <------------------------------------+ 0
+ X-Rc !
+ Y-Rp !
+ ^ !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! V
+ ! Y-Rc
+ 0 +------------------------------------->
+ 0 X-Rp
+
+ 270 degrees camera rotation:
+
+ 0 Y-Rc
+ 0 +-------------------->
+ ! 0
+ ! <-----------------------------------+ 0
+ ! X-Rp !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! !
+ ! V
+ ! Y-Rp
+ !
+ !
+ !
+ !
+ V
+ X-Rc
+
+
+ Example one - Webcam
+
+ A camera module installed on the user facing part of a laptop screen
+ casing used for video calls. The captured images are meant to be
+ displayed in landscape mode (width > height) on the laptop screen.
+
+ The camera is typically mounted upside-down to compensate the lens
+ optical inversion effect:
+
+ Y-Rp
+ Y-Rc ^
+ ^ !
+ ! !
+ ! ! |\_____)\__
+ ! ! ) ____ ___.<
+ ! ! |/ )/
+ ! !
+ ! !
+ ! !
+ ! 0 +------------------------------------->
+ ! 0 X-Rp
+ 0 +------------------------------------->
+ 0 X-Rc
+
+ The two reference systems are aligned, the resulting camera rotation is
+ 0 degrees, no rotation correction needs to be applied to the resulting
+ image once captured to memory buffers to correctly display it to users:
+
+ +--------------------------------------+
+ ! !
+ ! !
+ ! !
+ ! |\____)\___ !
+ ! ) _____ __`< !
+ ! |/ )/ !
+ ! !
+ ! !
+ ! !
+ +--------------------------------------+
+
+ If the camera sensor is not mounted upside-down to compensate for the
+ lens optical inversion, the two reference systems will not be aligned,
+ with 'Rp' being rotated 180 degrees relatively to 'Rc':
+
+
+ X-Rc 0
+ <------------------------------------+ 0
+ !
+ Y-Rp !
+ ^ !
+ ! !
+ ! |\_____)\__ !
+ ! ) ____ ___.< !
+ ! |/ )/ !
+ ! !
+ ! !
+ ! V
+ ! Y-Rc
+ 0 +------------------------------------->
+ 0 X-Rp
+
+ The image once captured to memory will then be rotated by 180 degrees:
+
+ +--------------------------------------+
+ ! !
+ ! !
+ ! !
+ ! __/(_____/| !
+ ! >.___ ____ ( !
+ ! \( \| !
+ ! !
+ ! !
+ ! !
+ +--------------------------------------+
+
+ A software rotation correction of 180 degrees should be applied to
+ correctly display the image:
+
+ +--------------------------------------+
+ ! !
+ ! !
+ ! !
+ ! |\____)\___ !
+ ! ) _____ __`< !
+ ! |/ )/ !
+ ! !
+ ! !
+ ! !
+ +--------------------------------------+
+
+ Example two - Phone camera
+
+ A camera installed on the back side of a mobile device facing away from
+ the user. The captured images are meant to be displayed in portrait mode
+ (height > width) to match the device screen orientation and the device
+ usage orientation used when taking the picture.
+
+ The camera sensor is typically mounted with its pixel array longer side
+ aligned to the device longer side, upside-down mounted to compensate for
+ the lens optical inversion effect:
+
+ 0 Y-Rc
+ 0 +-------------------->
+ ! Y-Rp
+ ! ^
+ ! !
+ ! !
+ ! !
+ ! ! |\_____)\__
+ ! ! ) ____ ___.<
+ ! ! |/ )/
+ ! !
+ ! !
+ ! !
+ ! 0 +------------------------------------->
+ ! 0 X-Rp
+ !
+ !
+ !
+ !
+ V
+ X-Rc
+
+ The two reference systems are not aligned and the 'Rp' reference
+ system is rotated by 90 degrees in the counter-clockwise direction
+ relatively to the 'Rc' reference system.
+
+ The image once captured to memory will be rotated:
+
+ +-------------------------------------+
+ | _ _ |
+ | \ / |
+ | | | |
+ | | | |
+ | | > |
+ | < | |
+ | | | |
+ | . |
+ | V |
+ +-------------------------------------+
+
+ A correction of 90 degrees in counter-clockwise direction has to be
+ applied to correctly display the image in portrait mode on the device
+ screen:
+
+ +--------------------+
+ | |
+ | |
+ | |
+ | |
+ | |
+ | |
+ | |\____)\___ |
+ | ) _____ __`< |
+ | |/ )/ |
+ | |
+ | |
+ | |
+ | |
+ | |
+ +--------------------+
+
+- orientation: The orientation of a device (typically an image sensor or a flash
+ LED) describing its mounting position relative to the usage orientation of the
+ system where the device is installed on.
+ Possible values are:
+ 0 - Front. The device is mounted on the front facing side of the system.
+ For mobile devices such as smartphones, tablets and laptops the front side is
+ the user facing side.
+ 1 - Back. The device is mounted on the back side of the system, which is
+ defined as the opposite side of the front facing one.
+ 2 - External. The device is not attached directly to the system but is
+ attached in a way that allows it to move freely.
+
+Optional endpoint properties
+----------------------------
+
+- remote-endpoint: phandle to an 'endpoint' subnode of a remote 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-type: data bus type. Possible values are:
+ 1 - MIPI CSI-2 C-PHY
+ 2 - MIPI CSI1
+ 3 - CCP2
+ 4 - MIPI CSI-2 D-PHY
+ 5 - Parallel
+ 6 - Bt.656
+- 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 the HSYNC signal, 0/1 for LOW/HIGH respectively.
+- vsync-active: active state of the 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.
+- data-enable-active: similar to HSYNC and VSYNC, specifies the data enable
+ signal 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.
+- sync-on-green-active: active state of Sync-on-green (SoG) signal, 0/1 for
+ LOW/HIGH respectively.
+- 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.
+ If the hardware does not support lane reordering, monotonically
+ incremented values shall be used from 0 or 1 onwards, depending on
+ whether or not there is also a clock lane. 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.
+- link-frequencies: Allowed data bus frequencies. For MIPI CSI-2, for
+ instance, this is the actual frequency of the bus, not bits per clock per
+ lane value. An array of 64-bit unsigned integers.
+- lane-polarities: an array of polarities of the lanes starting from the clock
+ lane and followed by the data lanes in the same order as in data-lanes.
+ Valid values are 0 (normal) and 1 (inverted). The length of the array
+ should be the combined length of data-lanes and clock-lanes properties.
+ If the lane-polarities property is omitted, the value must be interpreted
+ as 0 (normal). This property is valid for serial busses only.
+- strobe: Whether the clock signal is used as clock (0) or strobe (1). Used
+ with CCP2, for instance.
+
+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@fe910000 {
+ 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@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@0 {
+ reg = <0>;
+ remote = <&csi2_2>;
+ };
+ };
+ };
+
+ i2c0: i2c@fff20000 {
+ ...
+ ov772x_1: camera@21 {
+ compatible = "ovti,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@1a {
+ 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@ffc90000 {
+ compatible = "renesas,sh-mobile-csi2";
+ reg = <0xffc90000 0x1000>;
+ interrupts = <0x17a0>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ port@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@2 {
+ reg = <2>; /* port 2: link to the CEU */
+
+ csi2_2: endpoint {
+ remote-endpoint = <&ceu0_0>;
+ };
+ };
+ };