[RFC 1/1] doc-rst: Add Intel IPU3 documentation

* [RFC 1/1] doc-rst: Add Intel IPU3 documentation
@ 2018-12-13 11:45 Sakari Ailus
  2018-12-13 12:33 ` Laurent Pinchart
  0 siblings, 1 reply; 2+ messages in thread
From: Sakari Ailus @ 2018-12-13 11:45 UTC (permalink / raw)
  To: linux-media; +Cc: yong.zhi, laurent.pinchart, rajmohan.mani

From: Rajmohan Mani <rajmohan.mani@intel.com>

This patch adds the details about the IPU3 Imaging Unit driver (both CIO2
and IMGU).

Signed-off-by: Rajmohan Mani <rajmohan.mani@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
Hi Laurent,

Here's the original documentation patch with my changes folded into it.
The metadata format patch is needed before this one as it fixes the header
path as well.

I'm sending it as RFC as it's not intended to be merged.

 .../media/uapi/v4l/pixfmt-meta-intel-ipu3.rst      |   2 +-
 Documentation/media/v4l-drivers/index.rst          |   1 +
 Documentation/media/v4l-drivers/ipu3.rst           | 369 +++++++++++++++++++++
 drivers/staging/media/ipu3/TODO                    |  11 +
 4 files changed, 382 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/media/v4l-drivers/ipu3.rst

diff --git a/Documentation/media/uapi/v4l/pixfmt-meta-intel-ipu3.rst b/Documentation/media/uapi/v4l/pixfmt-meta-intel-ipu3.rst
index 8cd30ffbf8b8b..dc871006b41a5 100644
--- a/Documentation/media/uapi/v4l/pixfmt-meta-intel-ipu3.rst
+++ b/Documentation/media/uapi/v4l/pixfmt-meta-intel-ipu3.rst
@@ -175,4 +175,4 @@ video node in ``V4L2_BUF_TYPE_META_CAPTURE`` format.
 Intel IPU3 ImgU uAPI data types
 ===============================
 
-.. kernel-doc:: include/uapi/linux/intel-ipu3.h
+.. kernel-doc:: drivers/staging/media/ipu3/include/intel-ipu3.h
diff --git a/Documentation/media/v4l-drivers/index.rst b/Documentation/media/v4l-drivers/index.rst
index 6cdd3bc982023..f28570ec9e427 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 0000000000000..f89b51dafadd0
--- /dev/null
+++ b/Documentation/media/v4l-drivers/ipu3.rst
@@ -0,0 +1,369 @@
+.. include:: <isonum.txt>
+
+===============================================================
+Intel Image Processing Unit 3 (IPU3) Imaging Unit (ImgU) driver
+===============================================================
+
+Copyright |copy| 2018 Intel Corporation
+
+Introduction
+============
+
+This file documents the Intel IPU3 (3rd generation Image Processing Unit)
+Imaging Unit drivers located under drivers/media/pci/intel/ipu3 (CIO2) as well
+as under drivers/staging/media/ipu3 (ImgU).
+
+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 the Imaging Unit
+(ImgU) and the 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 the IPU3 (for consumption by the IPU3
+ImgU). The 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
+by the IPU3 CIO2 device. The ImgU driver sources can be found under
+drivers/staging/media/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 drivers has been tested on Kaby Lake platforms (U/Y processor lines).
+
+Both of the drivers implement V4L2, Media Controller and V4L2 sub-device
+interfaces. The IPU3 CIO2 driver supports camera sensors connected to the CIO2
+MIPI CSI-2 interfaces through V4L2 sub-device sensor drivers.
+
+CIO2
+====
+
+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.
+
+The CIO2 contains four independent capture channel, each with its own MIPI CSI-2
+receiver and DMA engine. Each channel is modelled as a V4L2 sub-device exposed
+to userspace as a V4L2 sub-device node and has two pads:
+
+.. tabularcolumns:: |p{0.8cm}|p{4.0cm}|p{4.0cm}|
+
+.. flat-table::
+
+    * - pad
+      - direction
+      - purpose
+
+    * - 0
+      - sink
+      - MIPI CSI-2 input, connected to the sensor subdev
+
+    * - 1
+      - source
+      - Raw video capture, connected to the V4L2 video interface
+
+The V4L2 video interfaces model the DMA engines. They are exposed to userspace
+as V4L2 video device nodes.
+
+Capturing frames in raw Bayer format
+------------------------------------
+
+CIO2 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 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 CIO2 media device
+
+export MDEV=/dev/media0
+
+# and that ov5670 sensor is connected to i2c bus 10 with address 0x36
+
+export SDEV=$(media-ctl -d $MDEV -e "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]"
+
+# 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 $SDEV
+
+yavta -w 0x009e0913 1024 $SDEV
+
+yavta -w 0x009e0911 2046 $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_SGRBG10 $(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_SGRBG10 format.
+
+The captured frames are available as /tmp/frame-#.bin files.
+
+ImgU
+====
+
+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.
+This helps to support advanced camera features like Continuous View Finder (CVF)
+and Snapshot During Video(SDV).
+
+The ImgU contains two independent pipes, each modelled as a V4L2 sub-device
+exposed to userspace as a V4L2 sub-device node.
+
+Each pipe has two sink pads and three source pads for the following purpose:
+
+.. tabularcolumns:: |p{0.8cm}|p{4.0cm}|p{4.0cm}|
+
+.. flat-table::
+
+    * - pad
+      - direction
+      - purpose
+
+    * - 0
+      - sink
+      - Input raw video stream
+
+    * - 1
+      - sink
+      - Processing parameters
+
+    * - 2
+      - source
+      - Output processed video stream
+
+    * - 3
+      - source
+      - Output viewfinder video stream
+
+    * - 4
+      - source
+      - 3A statistics
+
+Each pad is connected to a corresponding V4L2 video interface, exposed to 
+userspace as a V4L2 video device node.
+
+Device operation
+----------------
+
+With ImgU, once the input video node ("ipu3-imgu 0/1":0, in
+<entity>:<pad-number> format) is queued with buffer (in packed raw Bayer
+format), ImgU 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 the IPU3) received by the
+input video node is processed by the IPU3 Imaging Unit and are output to 2 video
+nodes, with each targeting a different purpose (main output and viewfinder
+output).
+
+Details onand the Bayer format specific to the IPU3 can be found in
+:ref:`v4l2-pix-fmt-ipu3-sbggr10`.
+
+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 parameters video node receives the ImgU algorithm parameters that are used
+to configure how the ImgU algorithms process the image.
+
+Details on processing parameters specific to the IPU3 can be found in
+:ref:`v4l2-meta-fmt-params`.
+
+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 ImgU to user space applications. User space applications
+can use this statistics data to compute the desired algorithm parameters for
+the ImgU.
+
+Configuring the Intel IPU3
+==========================
+
+The IPU3 ImgU pipelines can be configured using the Media Controller, defined at
+:ref:`media_controller`.
+
+Firmware binary selection
+-------------------------
+
+The firmware binary is selected using the V4L2_CID_INTEL_IPU3_MODE, currently
+defined in drivers/staging/media/ipu3/include/intel-ipu3.h . "VIDEO" and "STILL"
+modes are available.
+
+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 -> "ipu3-imgu 0 output":0[1]
+
+media-ctl -d $MDEV -l "ipu3-imgu 0":3 -> "ipu3-imgu 0 viewfinder":0[1]
+
+media-ctl -d $MDEV -l "ipu3-imgu 0":4 -> "ipu3-imgu 0 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.
+
+yavta -w "0x009819A1 1" /dev/v4l-subdev7
+
+RAW Bayer frames go through the following ImgU 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 ImgU
+configuration table.
+
+https://chromium.googlesource.com/chromiumos/overlays/board-overlays/+/master
+
+Under baseboard-poppy/media-libs/cros-camera-hal-configs-poppy/files/gcss
+directory, graph_settings_ov5670.xml can be used as an example.
+
+The following steps prepare the ImgU 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 [#f1]_.
+
+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=0X47337069
+--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.ppm
+
+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.ppm
+
+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
+==========
+
+.. [#f5] 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
diff --git a/drivers/staging/media/ipu3/TODO b/drivers/staging/media/ipu3/TODO
index 922b885f10a70..905bbb190217b 100644
--- a/drivers/staging/media/ipu3/TODO
+++ b/drivers/staging/media/ipu3/TODO
@@ -21,3 +21,14 @@ staging directory.
   Further clarification on some ambiguities such as data type conversion of
   IEFD CU inputs. (Sakari)
   Move acronyms to doc-rst file. (Mauro)
+
+- Switch to yavta from v4l2n in driver docs.
+
+- Elaborate the functionality of different selection rectangles in driver
+  documentation. This may require driver changes as well.
+
+- More detailed documentation on calculating BDS, GCD etc. sizes needed.
+
+- Document different operation modes, and which buffer queues are relevant
+  in each mode. To process an image, which queues require a buffer an in
+  which ones is it optional?
-- 
2.11.0


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