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October 7, 2018 03:17
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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. | |
ビデオデータパイプラインは外部のデバイスから構成されることが多い。例えばI2C,SPI,UARTバスおよび | |
VDMAやビデオデータプロセッサを含むSoC内部のIPブロックにより制御される。 | |
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. | |
SoC内部のブロックはデバイスツリーのノードにより記述される。他のSoCのブロクと同様に記述される。 | |
外部デバイスはI2Cなど、それぞれのバスコントローラの子ノードとして記述される。 | |
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. | |
すべてのビデオデバイスのデータインタフェースはそれぞれのport子ノードによって記述される | |
データ転送に関連する他のデバイスに依存するポートの設定はendpointサブノードによって記述される。 | |
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. | |
もしポートが1つのバス上で、複数のリモートデバイスと動作するように設定ができる場合、endpoint子ノードは各リモートデバイスごと | |
に必要となる。 | |
・2つ以上のポートがデバイスノードに存在する | |
・2つ以上のendpointが1つのポートに存在する | |
・portノードが1つの選択されたHWインタフェースと関連付けられる必要がある | |
これらの場合、共有スキームである#adress-cells, #size-cells, reg、これらのプロパティが使用される。 | |
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. | |
すべてのportノードは、オプションのportノードの下でグループ化できます。これにより、 | |
portノードとendpointノードとデバイスが持つ可能性がある子デバイスノードの#address-cells, #size-cellsプロパティを個別に指定できます。 | |
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. | |
2つのendpointノードはremote-endpointというphandleによってリンクされる。 | |
デバイスのエンドポイントサブノードはすべてのプロパティ | |
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 a 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 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: | |
0 - autodetect based on other properties (MIPI CSI-2 D-PHY, parallel or Bt656) | |
1 - MIPI CSI-2 C-PHY | |
2 - MIPI CSI1 | |
3 - CCP2 | |
- 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. | |
- 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. | |
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@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@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@0xfff20000 { | |
... | |
ov772x_1: camera@0x21 { | |
compatible = "ovti,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@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@0xffc90000 { | |
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>; | |
}; | |
}; | |
}; |
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