154 lines
5.3 KiB
ReStructuredText
154 lines
5.3 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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.. include:: <isonum.txt>
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The Samsung S5P/Exynos4 FIMC driver
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===================================
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Copyright |copy| 2012 - 2013 Samsung Electronics Co., Ltd.
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The FIMC (Fully Interactive Mobile Camera) device available in Samsung
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SoC Application Processors is an integrated camera host interface, color
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space converter, image resizer and rotator. It's also capable of capturing
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data from LCD controller (FIMD) through the SoC internal writeback data
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path. There are multiple FIMC instances in the SoCs (up to 4), having
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slightly different capabilities, like pixel alignment constraints, rotator
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availability, LCD writeback support, etc. The driver is located at
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drivers/media/platform/samsung/exynos4-is directory.
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Supported SoCs
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--------------
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S5PC100 (mem-to-mem only), S5PV210, Exynos4210
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Supported features
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------------------
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- camera parallel interface capture (ITU-R.BT601/565);
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- camera serial interface capture (MIPI-CSI2);
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- memory-to-memory processing (color space conversion, scaling, mirror
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and rotation);
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- dynamic pipeline re-configuration at runtime (re-attachment of any FIMC
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instance to any parallel video input or any MIPI-CSI front-end);
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- runtime PM and system wide suspend/resume
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Not currently supported
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-----------------------
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- LCD writeback input
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- per frame clock gating (mem-to-mem)
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User space interfaces
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---------------------
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Media device interface
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~~~~~~~~~~~~~~~~~~~~~~
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The driver supports Media Controller API as defined at :ref:`media_controller`.
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The media device driver name is "Samsung S5P FIMC".
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The purpose of this interface is to allow changing assignment of FIMC instances
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to the SoC peripheral camera input at runtime and optionally to control internal
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connections of the MIPI-CSIS device(s) to the FIMC entities.
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The media device interface allows to configure the SoC for capturing image
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data from the sensor through more than one FIMC instance (e.g. for simultaneous
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viewfinder and still capture setup).
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Reconfiguration is done by enabling/disabling media links created by the driver
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during initialization. The internal device topology can be easily discovered
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through media entity and links enumeration.
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Memory-to-memory video node
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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V4L2 memory-to-memory interface at /dev/video? device node. This is standalone
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video device, it has no media pads. However please note the mem-to-mem and
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capture video node operation on same FIMC instance is not allowed. The driver
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detects such cases but the applications should prevent them to avoid an
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undefined behaviour.
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Capture video node
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~~~~~~~~~~~~~~~~~~
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The driver supports V4L2 Video Capture Interface as defined at
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:ref:`devices`.
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At the capture and mem-to-mem video nodes only the multi-planar API is
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supported. For more details see: :ref:`planar-apis`.
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Camera capture subdevs
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~~~~~~~~~~~~~~~~~~~~~~
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Each FIMC instance exports a sub-device node (/dev/v4l-subdev?), a sub-device
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node is also created per each available and enabled at the platform level
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MIPI-CSI receiver device (currently up to two).
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sysfs
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~~~~~
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In order to enable more precise camera pipeline control through the sub-device
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API the driver creates a sysfs entry associated with "s5p-fimc-md" platform
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device. The entry path is: /sys/platform/devices/s5p-fimc-md/subdev_conf_mode.
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In typical use case there could be a following capture pipeline configuration:
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sensor subdev -> mipi-csi subdev -> fimc subdev -> video node
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When we configure these devices through sub-device API at user space, the
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configuration flow must be from left to right, and the video node is
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configured as last one.
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When we don't use sub-device user space API the whole configuration of all
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devices belonging to the pipeline is done at the video node driver.
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The sysfs entry allows to instruct the capture node driver not to configure
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the sub-devices (format, crop), to avoid resetting the subdevs' configuration
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when the last configuration steps at the video node is performed.
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For full sub-device control support (subdevs configured at user space before
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starting streaming):
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.. code-block:: none
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# echo "sub-dev" > /sys/platform/devices/s5p-fimc-md/subdev_conf_mode
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For V4L2 video node control only (subdevs configured internally by the host
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driver):
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.. code-block:: none
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# echo "vid-dev" > /sys/platform/devices/s5p-fimc-md/subdev_conf_mode
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This is a default option.
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5. Device mapping to video and subdev device nodes
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--------------------------------------------------
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There are associated two video device nodes with each device instance in
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hardware - video capture and mem-to-mem and additionally a subdev node for
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more precise FIMC capture subsystem control. In addition a separate v4l2
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sub-device node is created per each MIPI-CSIS device.
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How to find out which /dev/video? or /dev/v4l-subdev? is assigned to which
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device?
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You can either grep through the kernel log to find relevant information, i.e.
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.. code-block:: none
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# dmesg | grep -i fimc
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(note that udev, if present, might still have rearranged the video nodes),
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or retrieve the information from /dev/media? with help of the media-ctl tool:
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.. code-block:: none
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# media-ctl -p
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7. Build
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--------
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If the driver is built as a loadable kernel module (CONFIG_VIDEO_SAMSUNG_S5P_FIMC=m)
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two modules are created (in addition to the core v4l2 modules): s5p-fimc.ko and
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optional s5p-csis.ko (MIPI-CSI receiver subdev).
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