fimc.rst

  1.. SPDX-License-Identifier: GPL-2.0
  2
  3.. include:: <isonum.txt>
  4
  5The Samsung S5P/Exynos4 FIMC driver
  6===================================
  7
  8Copyright |copy| 2012 - 2013 Samsung Electronics Co., Ltd.
  9
 10The FIMC (Fully Interactive Mobile Camera) device available in Samsung
 11SoC Application Processors is an integrated camera host interface, color
 12space converter, image resizer and rotator.  It's also capable of capturing
 13data from LCD controller (FIMD) through the SoC internal writeback data
 14path.  There are multiple FIMC instances in the SoCs (up to 4), having
 15slightly different capabilities, like pixel alignment constraints, rotator
 16availability, LCD writeback support, etc. The driver is located at
 17drivers/media/platform/samsung/exynos4-is directory.
 18
 19Supported SoCs
 20--------------
 21
 22S5PC100 (mem-to-mem only), S5PV210, Exynos4210
 23
 24Supported features
 25------------------
 26
 27- camera parallel interface capture (ITU-R.BT601/565);
 28- camera serial interface capture (MIPI-CSI2);
 29- memory-to-memory processing (color space conversion, scaling, mirror
 30  and rotation);
 31- dynamic pipeline re-configuration at runtime (re-attachment of any FIMC
 32  instance to any parallel video input or any MIPI-CSI front-end);
 33- runtime PM and system wide suspend/resume
 34
 35Not currently supported
 36-----------------------
 37
 38- LCD writeback input
 39- per frame clock gating (mem-to-mem)
 40
 41User space interfaces
 42---------------------
 43
 44Media device interface
 45~~~~~~~~~~~~~~~~~~~~~~
 46
 47The driver supports Media Controller API as defined at :ref:`media_controller`.
 48The media device driver name is "Samsung S5P FIMC".
 49
 50The purpose of this interface is to allow changing assignment of FIMC instances
 51to the SoC peripheral camera input at runtime and optionally to control internal
 52connections of the MIPI-CSIS device(s) to the FIMC entities.
 53
 54The media device interface allows to configure the SoC for capturing image
 55data from the sensor through more than one FIMC instance (e.g. for simultaneous
 56viewfinder and still capture setup).
 57
 58Reconfiguration is done by enabling/disabling media links created by the driver
 59during initialization. The internal device topology can be easily discovered
 60through media entity and links enumeration.
 61
 62Memory-to-memory video node
 63~~~~~~~~~~~~~~~~~~~~~~~~~~~
 64
 65V4L2 memory-to-memory interface at /dev/video? device node.  This is standalone
 66video device, it has no media pads. However please note the mem-to-mem and
 67capture video node operation on same FIMC instance is not allowed.  The driver
 68detects such cases but the applications should prevent them to avoid an
 69undefined behaviour.
 70
 71Capture video node
 72~~~~~~~~~~~~~~~~~~
 73
 74The driver supports V4L2 Video Capture Interface as defined at
 75:ref:`devices`.
 76
 77At the capture and mem-to-mem video nodes only the multi-planar API is
 78supported. For more details see: :ref:`planar-apis`.
 79
 80Camera capture subdevs
 81~~~~~~~~~~~~~~~~~~~~~~
 82
 83Each FIMC instance exports a sub-device node (/dev/v4l-subdev?), a sub-device
 84node is also created per each available and enabled at the platform level
 85MIPI-CSI receiver device (currently up to two).
 86
 87sysfs
 88~~~~~
 89
 90In order to enable more precise camera pipeline control through the sub-device
 91API the driver creates a sysfs entry associated with "s5p-fimc-md" platform
 92device. The entry path is: /sys/platform/devices/s5p-fimc-md/subdev_conf_mode.
 93
 94In typical use case there could be a following capture pipeline configuration:
 95sensor subdev -> mipi-csi subdev -> fimc subdev -> video node
 96
 97When we configure these devices through sub-device API at user space, the
 98configuration flow must be from left to right, and the video node is
 99configured as last one.
100
101When we don't use sub-device user space API the whole configuration of all
102devices belonging to the pipeline is done at the video node driver.
103The sysfs entry allows to instruct the capture node driver not to configure
104the sub-devices (format, crop), to avoid resetting the subdevs' configuration
105when the last configuration steps at the video node is performed.
106
107For full sub-device control support (subdevs configured at user space before
108starting streaming):
109
110.. code-block:: none
111
112	# echo "sub-dev" > /sys/platform/devices/s5p-fimc-md/subdev_conf_mode
113
114For V4L2 video node control only (subdevs configured internally by the host
115driver):
116
117.. code-block:: none
118
119	# echo "vid-dev" > /sys/platform/devices/s5p-fimc-md/subdev_conf_mode
120
121This is a default option.
122
1235. Device mapping to video and subdev device nodes
124--------------------------------------------------
125
126There are associated two video device nodes with each device instance in
127hardware - video capture and mem-to-mem and additionally a subdev node for
128more precise FIMC capture subsystem control. In addition a separate v4l2
129sub-device node is created per each MIPI-CSIS device.
130
131How to find out which /dev/video? or /dev/v4l-subdev? is assigned to which
132device?
133
134You can either grep through the kernel log to find relevant information, i.e.
135
136.. code-block:: none
137
138	# dmesg | grep -i fimc
139
140(note that udev, if present, might still have rearranged the video nodes),
141
142or retrieve the information from /dev/media? with help of the media-ctl tool:
143
144.. code-block:: none
145
146	# media-ctl -p
147
1487. Build
149--------
150
151If the driver is built as a loadable kernel module (CONFIG_VIDEO_SAMSUNG_S5P_FIMC=m)
152two modules are created (in addition to the core v4l2 modules): s5p-fimc.ko and
153optional s5p-csis.ko (MIPI-CSI receiver subdev).