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-.. SPDX-License-Identifier: GPL-2.0
-.. _MIPI_CSI_2:
-CSI-2 is a data bus intended for transferring images from cameras to
-the host SoC. It is defined by the `MIPI alliance`_.
-.. _`MIPI alliance`: http://www.mipi.org/
-Media bus formats
-See :ref:`v4l2-mbus-pixelcode` for details on which media bus formats should
-be used for CSI-2 interfaces.
-Transmitter drivers
-CSI-2 transmitter, such as a sensor or a TV tuner, drivers need to
-provide the CSI-2 receiver with information on the CSI-2 bus
-configuration. These include the V4L2_CID_LINK_FREQ and
-V4L2_CID_PIXEL_RATE controls and
-(:c:type:`v4l2_subdev_video_ops`->s_stream() callback). These
-interface elements must be present on the sub-device represents the
-CSI-2 transmitter.
-The V4L2_CID_LINK_FREQ control is used to tell the receiver driver the
-frequency (and not the symbol rate) of the link. The V4L2_CID_PIXEL_RATE
-control may be used by the receiver to obtain the pixel rate the transmitter
-uses. The :c:type:`v4l2_subdev_video_ops`->s_stream() callback provides an
-ability to start and stop the stream.
-The value of the V4L2_CID_PIXEL_RATE is calculated as follows::
- pixel_rate = link_freq * 2 * nr_of_lanes * 16 / k / bits_per_sample
-.. list-table:: variables in pixel rate calculation
- :header-rows: 1
- * - variable or constant
- - description
- * - link_freq
- - The value of the V4L2_CID_LINK_FREQ integer64 menu item.
- * - nr_of_lanes
- - Number of data lanes used on the CSI-2 link. This can
- be obtained from the OF endpoint configuration.
- * - 2
- - Two bits are transferred per clock cycle per lane.
- * - bits_per_sample
- - Number of bits per sample.
- * - k
- - 16 for D-PHY and 7 for C-PHY
-The transmitter drivers must, if possible, configure the CSI-2
-transmitter to *LP-11 mode* whenever the transmitter is powered on but
-not active, and maintain *LP-11 mode* until stream on. Only at stream
-on should the transmitter activate the clock on the clock lane and
-transition to *HS mode*.
-Some transmitters do this automatically but some have to be explicitly
-programmed to do so, and some are unable to do so altogether due to
-hardware constraints.
-Stopping the transmitter
-A transmitter stops sending the stream of images as a result of
-calling the ``.s_stream()`` callback. Some transmitters may stop the
-stream at a frame boundary whereas others stop immediately,
-effectively leaving the current frame unfinished. The receiver driver
-should not make assumptions either way, but function properly in both
-Receiver drivers
-Before the receiver driver may enable the CSI-2 transmitter by using
-the :c:type:`v4l2_subdev_video_ops`->s_stream(), it must have powered
-the transmitter up by using the
-:c:type:`v4l2_subdev_core_ops`->s_power() callback. This may take
-place either indirectly by using :c:func:`v4l2_pipeline_pm_get` or
-The media bus pixel codes document parallel formats. Should the pixel data be
-transported over a serial bus, the media bus pixel code that describes a
-parallel format that transfers a sample on a single clock cycle is used.

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