Re: [PATCH v8 17/17] doc-rst: Add Intel IPU3 documentation

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hello Yong,

Thank you for the patch.

I've reviewed v7 of the IPU3 documentation in details, yet the comments don't 
seem to have been taken into account. Could you please address that in v9 ? I 
will skip review of v8 until then.

On Friday, 7 December 2018 03:03:42 EET Yong Zhi wrote:
> From: Rajmohan Mani <rajmohan.mani@intel.com>
> 
> This patch adds the details about the IPU3 Imaging Unit driver.
> 
> Change-Id: I560cecf673df2dcc3ec72767cf8077708d649656
> Signed-off-by: Rajmohan Mani <rajmohan.mani@intel.com>
> ---
>  Documentation/media/v4l-drivers/index.rst |   1 +
>  Documentation/media/v4l-drivers/ipu3.rst  | 326 +++++++++++++++++++++++++++
>  2 files changed, 327 insertions(+)
>  create mode 100644 Documentation/media/v4l-drivers/ipu3.rst
> 
> diff --git a/Documentation/media/v4l-drivers/index.rst
> b/Documentation/media/v4l-drivers/index.rst index
> 6cdd3bc98202..f28570ec9e42 100644
> --- a/Documentation/media/v4l-drivers/index.rst
> +++ b/Documentation/media/v4l-drivers/index.rst
> @@ -44,6 +44,7 @@ For more details see the file COPYING in the source
> distribution of Linux. davinci-vpbe
>  	fimc
>  	imx
> +	ipu3
>  	ivtv
>  	max2175
>  	meye
> diff --git a/Documentation/media/v4l-drivers/ipu3.rst
> b/Documentation/media/v4l-drivers/ipu3.rst new file mode 100644
> index 000000000000..045bf4222b1a
> --- /dev/null
> +++ b/Documentation/media/v4l-drivers/ipu3.rst
> @@ -0,0 +1,326 @@
> +.. include:: <isonum.txt>
> +
> +===============================================================
> +Intel Image Processing Unit 3 (IPU3) Imaging Unit (ImgU) driver
> +===============================================================
> +
> +Copyright |copy| 2018 Intel Corporation
> +
> +Introduction
> +============
> +
> +This file documents Intel IPU3 (3rd generation Image Processing Unit)
> Imaging +Unit driver located under drivers/media/pci/intel/ipu3.
> +
> +The Intel IPU3 found in certain Kaby Lake (as well as certain Sky Lake)
> +platforms (U/Y processor lines) is made up of two parts namely Imaging Unit
> +(ImgU) and CIO2 device (MIPI CSI2 receiver).
> +
> +The CIO2 device receives the raw bayer data from the sensors and outputs
> the +frames in a format that is specific to IPU3 (for consumption by IPU3
> ImgU). +CIO2 driver is available as drivers/media/pci/intel/ipu3/ipu3-cio2*
> and is +enabled through the CONFIG_VIDEO_IPU3_CIO2 config option.
> +
> +The Imaging Unit (ImgU) is responsible for processing images captured
> +through IPU3 CIO2 device. The ImgU driver sources can be found under
> +drivers/media/pci/intel/ipu3 directory. The driver is enabled through the
> +CONFIG_VIDEO_IPU3_IMGU config option.
> +
> +The two driver modules are named ipu3-csi2 and ipu3-imgu, respectively.
> +
> +The driver has been tested on Kaby Lake platforms (U/Y processor lines).
> +
> +The driver implements V4L2, Media controller and V4L2 sub-device
> interfaces. +Camera sensors that have CSI-2 bus, which are connected to the
> IPU3 CIO2 +device are supported. Support for lens and flash drivers depends
> on the +above sensors.
> +
> +ImgU device nodes
> +=================
> +
> +The ImgU is represented as two V4L2 subdevs, each of which provides a V4L2
> +subdev interface to the user space.
> +
> +Each V4L2 subdev represents a pipe, which can support a maximum of 2
> +streams. A private ioctl can be used to configure the mode (video or still)
> +of the pipe.
> +
> +This helps to support advanced camera features like Continuous View Finder
> +(CVF) and Snapshot During Video(SDV).
> +
> +CIO2 device
> +===========
> +
> +The CIO2 is represented as a single V4L2 subdev, which provides a V4L2
> subdev +interface to the user space. There is a video node for each CSI-2
> receiver, +with a single media controller interface for the entire device.
> +
> +Media controller
> +----------------
> +
> +The media device interface allows to configure the ImgU links, which
> defines +the behavior of the IPU3 firmware.
> +
> +Device operation
> +----------------
> +
> +With IPU3, once the input video node ("ipu3-imgu 0/1":0,
> +in <entity>:<pad-number> format) is queued with buffer (in packed raw bayer
> +format), IPU3 ISP starts processing the buffer and produces the video
> output +in YUV format and statistics output on respective output nodes. The
> driver +is expected to have buffers ready for all of parameter, output and
> +statistics nodes, when input video node is queued with buffer.
> +
> +At a minimum, all of input, main output, 3A statistics and viewfinder
> +video nodes should be enabled for IPU3 to start image processing.
> +
> +Each ImgU V4L2 subdev has the following set of video nodes.
> +
> +input, output and viewfinder video nodes
> +----------------------------------------
> +
> +The frames (in packed raw bayer format specific to IPU3) received by the
> +input video node is processed by the IPU3 Imaging Unit and is output to 2
> +video nodes, with each targeting different purpose (main output and
> viewfinder +output).
> +
> +Details on raw bayer format specific to IPU3 can be found as below.
> +Documentation/media/uapi/v4l/pixfmt-meta-intel-ipu3.rst
> +
> +The driver supports V4L2 Video Capture Interface as defined at
> :ref:`devices`. +
> +Only the multi-planar API is supported. More details can be found at
> +:ref:`planar-apis`.
> +
> +
> +parameters video node
> +---------------------
> +
> +The parameter video node receives the ISP algorithm parameters that are
> used +to configure how the ISP algorithms process the image.
> +
> +Details on raw bayer format specific to IPU3 can be found as below.
> +Documentation/media/uapi/v4l/pixfmt-meta-intel-ipu3.rst
> +
> +3A statistics video node
> +------------------------
> +
> +3A statistics video node is used by the ImgU driver to output the 3A (auto
> +focus, auto exposure and auto white balance) statistics for the frames that
> +are being processed by the ISP to user space applications. User space
> +applications can use this statistics data to arrive at desired algorithm
> +parameters for ISP.
> +
> +CIO2 device nodes
> +=================
> +
> +CIO2 is represented as a single V4L2 sub-device with a video node for each
> +CSI-2 receiver. The video node represents the DMA engine.
> +
> +Configuring the Intel IPU3
> +==========================
> +
> +The Intel IPU3 ImgU driver supports V4L2 interface. Using V4L2 ioctl calls,
> +the ISP can be configured and enabled.
> +
> +The IPU3 ImgU pipelines can be configured using media controller APIs,
> +defined at :ref:`media_controller`.
> +
> +Capturing frames in raw bayer format
> +------------------------------------
> +
> +IPU3 MIPI CSI2 receiver is used to capture frames (in packed raw bayer
> +format) from the raw sensors connected to the CSI2 ports. The captured
> +frames are used as input to the ImgU driver.
> +
> +Image processing using IPU3 ImgU requires tools such as v4l2n [#f1]_,
> +raw2pnm [#f1]_, and yavta [#f2]_ due to the following unique requirements
> +and / or features specific to IPU3.
> +
> +-- The IPU3 CSI2 receiver outputs the captured frames from the sensor in
> +packed raw bayer format that is specific to IPU3
> +
> +-- Multiple video nodes have to be operated simultaneously
> +
> +Let us take the example of ov5670 sensor connected to CSI2 port 0, for a
> +2592x1944 image capture.
> +
> +Using the media contorller APIs, the ov5670 sensor is configured to send
> +frames in packed raw bayer format to IPU3 CSI2 receiver.
> +
> +# This example assumes /dev/media0 as the ImgU media device
> +
> +export MDEV=/dev/media0
> +
> +# and that ov5670 sensor is connected to i2c bus 10 with address 0x36
> +
> +export SDEV="ov5670 10-0036"
> +
> +# Establish the link for the media devices using media-ctl [#f3]_
> +media-ctl -d $MDEV -l "ov5670 ":0 -> "ipu3-csi2 0":0[1]
> +
> +media-ctl -d $MDEV -l "ipu3-csi2 0":1 -> "ipu3-cio2 0":0[1]
> +
> +# Set the format for the media devices
> +media-ctl -d $MDEV -V "ov5670 ":0 [fmt:SGRBG10/2592x1944]
> +
> +media-ctl -d $MDEV -V "ipu3-csi2 0":0 [fmt:SGRBG10/2592x1944]
> +
> +media-ctl -d $MDEV -V "ipu3-csi2 0":1 [fmt:SGRBG10/2592x1944]
> +
> +Once the media pipeline is configured, desired sensor specific settings
> +(such as exposure and gain settings) can be set, using the yavta tool.
> +
> +e.g
> +
> +yavta -w 0x009e0903 444 $(media-ctl -d $MDEV -e "$SDEV")
> +
> +yavta -w 0x009e0913 1024 $(media-ctl -d $MDEV -e "$SDEV")
> +
> +yavta -w 0x009e0911 2046 $(media-ctl -d $MDEV -e "$SDEV")
> +
> +Once the desired sensor settings are set, frame captures can be done as
> below. +
> +e.g
> +
> +yavta --data-prefix -u -c10 -n5 -I -s2592x1944 --file=/tmp/frame-#.bin
> +-f IPU3_GRBG10 media-ctl -d $MDEV -e ipu3-cio2 0
> +
> +With the above command, 10 frames are captured at 2592x1944 resolution,
> with +sGRBG10 format and output as IPU3_GRBG10 format.
> +
> +The captured frames are available as /tmp/frame-#.bin files.
> +
> +Processing the image in raw bayer format
> +----------------------------------------
> +
> +Configuring ImgU V4L2 subdev for image processing
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +The ImgU V4L2 subdevs have to be configured with media controller APIs to
> +have all the video nodes setup correctly.
> +
> +Let us take "ipu3-imgu 0" subdev as an example.
> +
> +media-ctl -d $MDEV -r
> +
> +media-ctl -d $MDEV -l "ipu3-imgu 0 input":0 -> "ipu3-imgu 0":0[1]
> +
> +media-ctl -d $MDEV -l "ipu3-imgu 0":2 -> "output":0[1]
> +
> +media-ctl -d $MDEV -l "ipu3-imgu 0":3 -> "viewfinder":0[1]
> +
> +media-ctl -d $MDEV -l "ipu3-imgu 0":4 -> "3a stat":0[1]
> +
> +Also the pipe mode of the corresponding V4L2 subdev should be set as
> +desired (e.g 0 for video mode or 1 for still mode) through the
> +control id 0x009819a1 as below.
> +
> +e.g
> +
> +v4l2n -d /dev/v4l-subdev7 --ctrl=0x009819A1=1
> +
> +RAW bayer frames go through the following ISP pipeline HW blocks to
> +have the processed image output to the DDR memory.
> +
> +RAW bayer frame -> Input Feeder -> Bayer Down Scaling (BDS) -> Geometric
> +Distortion Correction (GDC) -> DDR
> +
> +The ImgU V4L2 subdev has to be configured with the supported resolutions
> +in all the above HW blocks, for a given input resolution.
> +
> +For a given supported resolution for an input frame, the Input Feeder,
> +Bayer Down Scaling and GDC blocks should be configured with the supported
> +resolutions. This information can be obtained by looking at the following
> +IPU3 ISP configuration table.
> +
> +https://chromium.googlesource.com/chromiumos/overlays/board-overlays/+/mast
> er +
> +Under baseboard-poppy/media-libs/arc-camera3-hal-configs-poppy/files/gcss
> +directory, graph_settings_ov5670.xml can be used as an example.
> +
> +The following steps prepare the ImgU ISP pipeline for the image processing.
> +
> +1. The ImgU V4L2 subdev data format should be set by using the
> +VIDIOC_SUBDEV_S_FMT on pad 0, using the GDC width and height obtained
> above. +
> +2. The ImgU V4L2 subdev cropping should be set by using the
> +VIDIOC_SUBDEV_S_SELECTION on pad 0, with V4L2_SEL_TGT_CROP as the target,
> +using the input feeder height and width.
> +
> +3. The ImgU V4L2 subdev composing should be set by using the
> +VIDIOC_SUBDEV_S_SELECTION on pad 0, with V4L2_SEL_TGT_COMPOSE as the
> target, +using the BDS height and width.
> +
> +For the ov5670 example, for an input frame with a resolution of 2592x1944
> +(which is input to the ImgU subdev pad 0), the corresponding resolutions
> +for input feeder, BDS and GDC are 2592x1944, 2592x1944 and 2560x1920
> +respectively.
> +
> +Once this is done, the received raw bayer frames can be input to the ImgU
> +V4L2 subdev as below, using the open source application v4l2n.
> +
> +For an image captured with 2592x1944 [#f4]_ resolution, with desired output
> +resolution as 2560x1920 and viewfinder resolution as 2560x1920, the
> following +v4l2n command can be used. This helps process the raw bayer
> frames and +produces the desired results for the main output image and the
> viewfinder +output, in NV12 format.
> +
> +v4l2n --pipe=4 --load=/tmp/frame-#.bin --open=/dev/video4
> +--fmt=type:VIDEO_OUTPUT_MPLANE,width=2592,height=1944,pixelformat=0X4733706
> 9 +--reqbufs=type:VIDEO_OUTPUT_MPLANE,count:1 --pipe=1
> --output=/tmp/frames.out +--open=/dev/video5
> +--fmt=type:VIDEO_CAPTURE_MPLANE,width=2560,height=1920,pixelformat=NV12
> +--reqbufs=type:VIDEO_CAPTURE_MPLANE,count:1 --pipe=2
> --output=/tmp/frames.vf +--open=/dev/video6
> +--fmt=type:VIDEO_CAPTURE_MPLANE,width=2560,height=1920,pixelformat=NV12
> +--reqbufs=type:VIDEO_CAPTURE_MPLANE,count:1 --pipe=3 --open=/dev/video7
> +--output=/tmp/frames.3A --fmt=type:META_CAPTURE,?
> +--reqbufs=count:1,type:META_CAPTURE --pipe=1,2,3,4 --stream=5
> +
> +where /dev/video4, /dev/video5, /dev/video6 and /dev/video7 devices point
> to +input, output, viewfinder and 3A statistics video nodes respectively. +
> +Converting the raw bayer image into YUV domain
> +----------------------------------------------
> +
> +The processed images after the above step, can be converted to YUV domain
> +as below.
> +
> +Main output frames
> +~~~~~~~~~~~~~~~~~~
> +
> +raw2pnm -x2560 -y1920 -fNV12 /tmp/frames.out /tmp/frames.out.pnm
> +
> +where 2560x1920 is output resolution, NV12 is the video format, followed
> +by input frame and output PNM file.
> +
> +Viewfinder output frames
> +~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +raw2pnm -x2560 -y1920 -fNV12 /tmp/frames.vf /tmp/frames.vf.pnm
> +
> +where 2560x1920 is output resolution, NV12 is the video format, followed
> +by input frame and output PNM file.
> +
> +Example user space code for IPU3
> +================================
> +
> +User space code that configures and uses IPU3 is available here.
> +
> +https://chromium.googlesource.com/chromiumos/platform/arc-camera/+/master/
> +
> +The source can be located under hal/intel directory.
> +
> +References
> +==========
> +
> +include/uapi/linux/intel-ipu3.h
> +
> +.. [#f1] https://github.com/intel/nvt
> +
> +.. [#f2] http://git.ideasonboard.org/yavta.git
> +
> +.. [#f3] http://git.ideasonboard.org/?p=media-ctl.git;a=summary
> +
> +.. [#f4] ImgU limitation requires an additional 16x16 for all input
> resolutions

-- 
Regards,

Laurent Pinchart