aboutsummaryrefslogtreecommitdiffstats
path: root/Documentation/driver-api/media/csi2.rst
diff options
context:
space:
mode:
authorSakari Ailus <sakari.ailus@linux.intel.com>2021-02-01 10:16:03 +0100
committerMauro Carvalho Chehab <mchehab+huawei@kernel.org>2021-08-04 14:43:50 +0200
commitb9a543364299e09ba236c69acb021ebbf7cebf1a (patch)
treec1bf41a74d88b37c9609ea0bae82442ce5eb2468 /Documentation/driver-api/media/csi2.rst
parent0368e7d2cd84a90d0518753fac33795e13df553f (diff)
media: Documentation: media: Improve camera sensor documentation
Modernise the documentation to make it more precise and update the use of pixel rate control and various other changes. In particular: - Use non-proportional font for file names, properties as well as controls. - The unit of the HBLANK control is pixels, not lines. - The unit of PIXEL_RATE control is pixels per second, not Hz. - Merge common requirements for CSI-2 and parallel busses. - Include all DT properties needed for assigned clocks. - Fix referencing the link rate control. - SMIA driver's new name is CCS driver. - The PIXEL_RATE control denotes pixel rate on the pixel array on camera sensors. Do not suggest it is used to tell the maximum pixel rate on the bus anymore. - Improve ReST syntax (plain struct and function names). - Remove the suggestion to use s_power() in receiver drivers. - Make MIPI website URL use HTTPS, add Wikipedia links to BT.601 and BT.656. Fixes: e4cf8c58af75 ("media: Documentation: media: Document how to write camera sensor drivers") Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org> Reviewed-by: Andrey Konovalov <andrey.konovalov@linaro.org> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Diffstat (limited to 'Documentation/driver-api/media/csi2.rst')
-rw-r--r--Documentation/driver-api/media/csi2.rst94
1 files changed, 0 insertions, 94 deletions
diff --git a/Documentation/driver-api/media/csi2.rst b/Documentation/driver-api/media/csi2.rst
deleted file mode 100644
index 11c52b0be8b8..000000000000
--- a/Documentation/driver-api/media/csi2.rst
+++ /dev/null
@@ -1,94 +0,0 @@
-.. SPDX-License-Identifier: GPL-2.0
-
-.. _MIPI_CSI_2:
-
-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
-
-where
-
-.. 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
-cases.
-
-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
-directly.
-
-Formats
--------
-
-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.

Privacy Policy