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media: admin-guide: Document the Raspberry Pi CFE (rp1-cfe)
Add documentation for rp1-cfe driver.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
authored by
Tomi Valkeinen
and committed by
Mauro Carvalho Chehab
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6edb685a
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Documentation/admin-guide/media/raspberrypi-rp1-cfe.dot
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Documentation/admin-guide/media/raspberrypi-rp1-cfe.dot
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digraph board {
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rankdir=TB
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n00000001 [label="{{<port0> 0} | csi2\n/dev/v4l-subdev0 | {<port1> 1 | <port2> 2 | <port3> 3 | <port4> 4}}", shape=Mrecord, style=filled, fillcolor=green]
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n00000001:port1 -> n00000011 [style=dashed]
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n00000001:port1 -> n00000007:port0
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n00000001:port2 -> n00000015
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n00000001:port2 -> n00000007:port0 [style=dashed]
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n00000001:port3 -> n00000019 [style=dashed]
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n00000001:port3 -> n00000007:port0 [style=dashed]
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n00000001:port4 -> n0000001d [style=dashed]
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n00000001:port4 -> n00000007:port0 [style=dashed]
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n00000007 [label="{{<port0> 0 | <port1> 1} | pisp-fe\n/dev/v4l-subdev1 | {<port2> 2 | <port3> 3 | <port4> 4}}", shape=Mrecord, style=filled, fillcolor=green]
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n00000007:port2 -> n00000021
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n00000007:port3 -> n00000025 [style=dashed]
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n00000007:port4 -> n00000029
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n0000000d [label="{imx219 6-0010\n/dev/v4l-subdev2 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
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n0000000d:port0 -> n00000001:port0 [style=bold]
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n00000011 [label="rp1-cfe-csi2-ch0\n/dev/video0", shape=box, style=filled, fillcolor=yellow]
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n00000015 [label="rp1-cfe-csi2-ch1\n/dev/video1", shape=box, style=filled, fillcolor=yellow]
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n00000019 [label="rp1-cfe-csi2-ch2\n/dev/video2", shape=box, style=filled, fillcolor=yellow]
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n0000001d [label="rp1-cfe-csi2-ch3\n/dev/video3", shape=box, style=filled, fillcolor=yellow]
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n00000021 [label="rp1-cfe-fe-image0\n/dev/video4", shape=box, style=filled, fillcolor=yellow]
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n00000025 [label="rp1-cfe-fe-image1\n/dev/video5", shape=box, style=filled, fillcolor=yellow]
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n00000029 [label="rp1-cfe-fe-stats\n/dev/video6", shape=box, style=filled, fillcolor=yellow]
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n0000002d [label="rp1-cfe-fe-config\n/dev/video7", shape=box, style=filled, fillcolor=yellow]
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n0000002d -> n00000007:port1
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}
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Documentation/admin-guide/media/raspberrypi-rp1-cfe.rst
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Documentation/admin-guide/media/raspberrypi-rp1-cfe.rst
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.. SPDX-License-Identifier: GPL-2.0
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============================================
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Raspberry Pi PiSP Camera Front End (rp1-cfe)
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============================================
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The PiSP Camera Front End
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=========================
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The PiSP Camera Front End (CFE) is a module which combines a CSI-2 receiver with
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a simple ISP, called the Front End (FE).
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The CFE has four DMA engines and can write frames from four separate streams
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received from the CSI-2 to the memory. One of those streams can also be routed
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directly to the FE, which can do minimal image processing, write two versions
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(e.g. non-scaled and downscaled versions) of the received frames to memory and
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provide statistics of the received frames.
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The FE registers are documented in the `Raspberry Pi Image Signal Processor
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(ISP) Specification document
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<https://datasheets.raspberrypi.com/camera/raspberry-pi-image-signal-processor-specification.pdf>`_,
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and example code for FE can be found in `libpisp
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<https://github.com/raspberrypi/libpisp>`_.
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The rp1-cfe driver
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==================
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The Raspberry Pi PiSP Camera Front End (rp1-cfe) driver is located under
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drivers/media/platform/raspberrypi/rp1-cfe. It uses the `V4L2 API` to register
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a number of video capture and output devices, the `V4L2 subdev API` to register
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subdevices for the CSI-2 received and the FE that connects the video devices in
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a single media graph realized using the `Media Controller (MC) API`.
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The media topology registered by the `rp1-cfe` driver, in this particular
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example connected to an imx219 sensor, is the following one:
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.. _rp1-cfe-topology:
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.. kernel-figure:: raspberrypi-rp1-cfe.dot
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:alt: Diagram of an example media pipeline topology
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:align: center
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The media graph contains the following video device nodes:
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- rp1-cfe-csi2-ch0: capture device for the first CSI-2 stream
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- rp1-cfe-csi2-ch1: capture device for the second CSI-2 stream
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- rp1-cfe-csi2-ch2: capture device for the third CSI-2 stream
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- rp1-cfe-csi2-ch3: capture device for the fourth CSI-2 stream
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- rp1-cfe-fe-image0: capture device for the first FE output
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- rp1-cfe-fe-image1: capture device for the second FE output
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- rp1-cfe-fe-stats: capture device for the FE statistics
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- rp1-cfe-fe-config: output device for FE configuration
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rp1-cfe-csi2-chX
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----------------
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The rp1-cfe-csi2-chX capture devices are normal V4L2 capture devices which
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can be used to capture video frames or metadata received from the CSI-2.
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rp1-cfe-fe-image0, rp1-cfe-fe-image1
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------------------------------------
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The rp1-cfe-fe-image0 and rp1-cfe-fe-image1 capture devices are used to write
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the processed frames to memory.
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rp1-cfe-fe-stats
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----------------
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The format of the FE statistics buffer is defined by
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:c:type:`pisp_statistics` C structure and the meaning of each parameter is
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described in the `PiSP specification` document.
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rp1-cfe-fe-config
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-----------------
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The format of the FE configuration buffer is defined by
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:c:type:`pisp_fe_config` C structure and the meaning of each parameter is
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described in the `PiSP specification` document.