[PATCH v2 2/2] media: admin-guide: add documentation file rkisp1.rst

Dafna Hirschfeld dafna.hirschfeld at collabora.com
Tue Aug 18 06:27:03 EDT 2020

Add the file 'rkisp1.rst' that documents the rkisp1 driver.

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld at collabora.com>
 Documentation/admin-guide/media/rkisp1.dot    |  18 ++
 Documentation/admin-guide/media/rkisp1.rst    | 181 ++++++++++++++++++
 .../admin-guide/media/v4l-drivers.rst         |   1 +
 3 files changed, 200 insertions(+)
 create mode 100644 Documentation/admin-guide/media/rkisp1.dot
 create mode 100644 Documentation/admin-guide/media/rkisp1.rst

diff --git a/Documentation/admin-guide/media/rkisp1.dot b/Documentation/admin-guide/media/rkisp1.dot
new file mode 100644
index 000000000000..54c1953a6130
--- /dev/null
+++ b/Documentation/admin-guide/media/rkisp1.dot
@@ -0,0 +1,18 @@
+digraph board {
+	rankdir=TB
+	n00000001 [label="{{<port0> 0 | <port1> 1} | rkisp1_isp\n/dev/v4l-subdev0 | {<port2> 2 | <port3> 3}}", shape=Mrecord, style=filled, fillcolor=green]
+	n00000001:port2 -> n00000006:port0
+	n00000001:port2 -> n00000009:port0
+	n00000001:port3 -> n00000014 [style=bold]
+	n00000006 [label="{{<port0> 0} | rkisp1_resizer_mainpath\n/dev/v4l-subdev1 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
+	n00000006:port1 -> n0000000c [style=bold]
+	n00000009 [label="{{<port0> 0} | rkisp1_resizer_selfpath\n/dev/v4l-subdev2 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
+	n00000009:port1 -> n00000010 [style=bold]
+	n0000000c [label="rkisp1_mainpath\n/dev/video0", shape=box, style=filled, fillcolor=yellow]
+	n00000010 [label="rkisp1_selfpath\n/dev/video1", shape=box, style=filled, fillcolor=yellow]
+	n00000014 [label="rkisp1_stats\n/dev/video2", shape=box, style=filled, fillcolor=yellow]
+	n00000018 [label="rkisp1_params\n/dev/video3", shape=box, style=filled, fillcolor=yellow]
+	n00000018 -> n00000001:port1 [style=bold]
+	n0000001c [label="{{} | imx219 4-0010\n/dev/v4l-subdev3 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
+	n0000001c:port0 -> n00000001:port0
diff --git a/Documentation/admin-guide/media/rkisp1.rst b/Documentation/admin-guide/media/rkisp1.rst
new file mode 100644
index 000000000000..42e37ed255f6
--- /dev/null
+++ b/Documentation/admin-guide/media/rkisp1.rst
@@ -0,0 +1,181 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+Rockchip Image Signal Processor (rkisp1)
+This file documents the driver for the Rockchip ISP1 that is part of RK3288
+and RK3399 SoCs. The driver is located under drivers/staging/media/rkisp1
+and uses the Media-Controller API.
+.. _rkisp1_topology_graph:
+.. kernel-figure:: rkisp1.dot
+    :alt:   Diagram of the default media pipeline topology
+    :align: center
+The driver has 4 video devices:
+- rkisp1_mainpath: capture device for retrieving images, usually in higher
+  resolution.
+- rkisp1_selfpath: capture device for retrieving images.
+- rkisp1_stats: a metadata capture device that sends statistics.
+- rkisp1_params: a metadata output device that receives parameters
+  configurations from userspace.
+The driver has 3 subdevices:
+- rkisp1_resizer_mainpath: used to resize and downsample frames for the
+  mainpath capture device.
+- rkisp1_resizer_selfpath: used to resize and downsample frames for the
+  selfpath capture device.
+- rkisp1_isp: is connected to the sensor and is responsible for all the isp
+  operations.
+rkisp1_mainpath, rkisp1_selfpath - Frames Capture Video Nodes
+Those are the `mainpath` and `selfpath` capture devices to capture frames.
+Those entities are the DMA engines that write the frames to memory.
+The selfpath video device can capture YUV/RGB formats. Its input is YUV encoded
+stream and it is able to convert it to RGB. The selfpath is not able to
+capture bayer formats.
+The mainpath can capture both bayer and YUV formats but it is not able to
+capture RGB formats.
+Both capture videos support
+the ``V4L2_CAP_IO_MC`` :ref:`capability <device-capabilities>`.
+rkisp1_resizer_mainpath, rkisp1_resizer_selfpath - Resizers Subdevices Nodes
+Those are resizer entities for the mainpath and the selfpath. Those entities
+can scale the frames up and down and also change the YUV sampling (for example
+YUV4:2:2 -> YUV4:2:0). They also have cropping capability on the sink pad.
+The resizers entities can only operate on YUV:4:2:2 format
+The mainpath capture device supports capturing video in bayer formats. In that
+case the resizer of the mainpath is set to 'bypass' mode - it just forward the
+frame without operating on it.
+rkisp1_isp - Image Signal Processing Subdevice Node
+This is the isp entity. It is connected to the sensor on sink pad 0 and
+receives the frames using the CSI-2 protocol. It is responsible of configuring
+the CSI-2 protocol. It has a cropping capability on sink pad 0 that is
+connected to the sensor and on source pad 2 connected to the resizer entities.
+Cropping on sink pad 0 defines the image region from the sensor.
+Cropping on source pad 2 defines the region for the Image Stabilizer (IS).
+.. _rkisp1_stats:
+rkisp1_stats - Statistics Video Node
+The statistics video node outputs the 3A (auto focus, auto exposure and auto
+white balance) statistics, and also histogram statistics for the frames that
+are being processed by the rkisp1 to userspace applications.
+Using these data, applications can implement algorithms and re-parameterize
+the driver through the rkisp_params node to improve image quality during a
+video stream.
+The buffer format is defined by struct :c:type:`rkisp1_stat_buffer`, and
+userspace should set
+:ref:`V4L2_META_FMT_RK_ISP1_STAT_3A <v4l2-meta-fmt-stat-rkisp1>` as the
+.. _rkisp1_params:
+rkisp1_params - Parameters Video Node
+The rkisp1_params video node receives a set of parameters from userspace
+to be applied to the hardware during a video stream, allowing userspace
+to dynamically modify values such as black level, cross talk corrections
+and others.
+The buffer format is defined by struct :c:type:`rkisp1_params_cfg`, and
+userspace should set
+:ref:`V4L2_META_FMT_RK_ISP1_PARAMS <v4l2-meta-fmt-params-rkisp1>` as the
+Capturing Video Frames Example
+In the following example, the sensor connected to pad 0 of 'rkisp1_isp' is
+The following commands can be used to capture video from the selfpath video
+node with dimension 900x800 planar format YUV 4:2:2. It uses all cropping
+capabilities possible, (see explanation right below)
+.. code-block:: bash
+	# set the links
+	"media-ctl" "-d" "platform:rkisp1" "-r"
+	"media-ctl" "-d" "platform:rkisp1" "-l" "'imx219 4-0010':0 -> 'rkisp1_isp':0 [1]"
+	"media-ctl" "-d" "platform:rkisp1" "-l" "'rkisp1_isp':2 -> 'rkisp1_resizer_selfpath':0 [1]"
+	"media-ctl" "-d" "platform:rkisp1" "-l" "'rkisp1_isp':2 -> 'rkisp1_resizer_mainpath':0 [0]"
+	# set format for imx219 4-0010:0
+	"media-ctl" "-d" "platform:rkisp1" "--set-v4l2" '"imx219 4-0010":0 [fmt:SRGGB10_1X10/1640x1232]'
+	# set format for rkisp1_isp pads:
+	"media-ctl" "-d" "platform:rkisp1" "--set-v4l2" '"rkisp1_isp":0 [fmt:SRGGB10_1X10/1640x1232 crop: (0,0)/1600x1200]'
+	"media-ctl" "-d" "platform:rkisp1" "--set-v4l2" '"rkisp1_isp":2 [fmt:YUYV8_2X8/1600x1200 crop: (0,0)/1500x1100]'
+	# set format for rkisp1_resizer_selfpath pads:
+	"media-ctl" "-d" "platform:rkisp1" "--set-v4l2" '"rkisp1_resizer_selfpath":0 [fmt:YUYV8_2X8/1500x1100 crop: (300,400)/1400x1000]'
+	"media-ctl" "-d" "platform:rkisp1" "--set-v4l2" '"rkisp1_resizer_selfpath":1 [fmt:YUYV8_2X8/900x800]'
+	# set format for rkisp1_selfpath:
+	"v4l2-ctl" "-z" "platform:rkisp1" "-d" "rkisp1_selfpath" "-v" "width=900,height=800,"
+	"v4l2-ctl" "-z" "platform:rkisp1" "-d" "rkisp1_selfpath" "-v" "pixelformat=422P"
+	# start streaming:
+	v4l2-ctl "-z" "platform:rkisp1" "-d" "rkisp1_selfpath" "--stream-mmap" "--stream-count" "10"
+In the above example the sensor is configured to bayer format:
+`SRGGB10_1X10/1640x1232`. The rkisp1_isp:0 pad should be configured to the
+same mbus format and dimensions as the sensor, otherwise streaming will fail
+with 'EPIPE' error. So it is also configured to `SRGGB10_1X10/1640x1232`.
+In addition, the rkisp1_isp:0 pad is configured to cropping `(0,0)/1600x1200`.
+The cropping dimensions are automatically propagated to be the format of the
+isp source pad `rkisp1_isp:2`. Another cropping operation is configured on
+the isp source pad: `(0,0)/1500x1100`.
+The resizer's sink pad `rkisp1_resizer_selfpath` should be configured to format
+`YUYV8_2X8/1500x1100` in order to match the format on the other side of the
+link. In addition a cropping `(300,400)/1400x1000` is configured on it.
+The source pad of the resizer, `rkisp1_resizer_selfpath:1` is configured to
+format `YUYV8_2X8/900x800`. That means that the resizer first crop a window
+of `(300,400)/1400x100` from the received frame and then scales this window
+to dimension `900x800`.
+Note that the above example does not uses the stats-params control loop.
+Therefore the capture frames will not go through the 3A algorithms and
+probably won't have a good quality, and can even look dark and greenish.
+Configuring Quantization
+The driver supports limited and full range quantization on YUV formats,
+where limited is the default.
+To switch between one or the other, userspace should use the Colorspace
+Conversion API (CSC) for subdevices on source pad 2 of the
+isp (`rkisp1_isp:2`). The quantization configured on this pad is the
+quantization of the captured video frames on the mainpath and selfpath
+video nodes.
+Note that the resizer and capture entities will always report
+``V4L2_QUANTIZATION_DEFAULT`` even if the quantization is configured to full
+range on `rkisp1_isp:2`. So in order to get the configured quantization,
+application should get it from pad `rkisp1_isp:2`.
diff --git a/Documentation/admin-guide/media/v4l-drivers.rst b/Documentation/admin-guide/media/v4l-drivers.rst
index 251cc4ede0b6..9c7ebe2ca3bd 100644
--- a/Documentation/admin-guide/media/v4l-drivers.rst
+++ b/Documentation/admin-guide/media/v4l-drivers.rst
@@ -25,6 +25,7 @@ Video4Linux (V4L) driver-specific documentation
+	rkisp1

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