driver-api/media/tx-rx.rst

1 .. SPDX-License-Identifier: GPL-2.0
3 .. _transmitter-receiver:
9 these devices include a camera sensor, a TV tuner and a parallel or a CSI-2
13 ---------
17 MIPI CSI-2
20 CSI-2 is a data bus intended for transferring images from cameras to
21 the host SoC. It is defined by the `MIPI alliance`_.
23 .. _`MIPI alliance`: https://www.mipi.org/
31 .. _`BT.656`: https://en.wikipedia.org/wiki/ITU-R_BT.656
34 -------------------
43 See :ref:`v4l2-mbus-pixelcode`.
48 The :ref:`V4L2_CID_LINK_FREQ <v4l2-cid-link-freq>` control is used to tell the
54 The struct struct v4l2_subdev_video_ops->s_stream() callback is used by the
58 CSI-2 transmitter drivers
59 -------------------------
70 .. list-table:: variables in pixel rate calculation
71    :header-rows: 1
73    * - variable or constant
74      - description
75    * - link_freq
76      - The value of the ``V4L2_CID_LINK_FREQ`` integer64 menu item.
77    * - nr_of_lanes
78      - Number of data lanes used on the CSI-2 link. This can
80    * - 2
81      - Data is transferred on both rising and falling edge of the signal.
82    * - bits_per_sample
83      - Number of bits per sample.
84    * - k
85      - 16 for D-PHY and 7 for C-PHY
91 	:ref:`V4L2_CID_PIXEL_RATE <v4l2-cid-pixel-rate>` control.
93 LP-11 and LP-111 modes
96 As part of transitioning to high speed mode, a CSI-2 transmitter typically
97 briefly sets the bus to LP-11 or LP-111 state, depending on the PHY. This period
103 involvement in observing LP-11 or LP-111 state. 100 µs is a brief period to hit
107 One way to address this is to configure the transmitter side explicitly to LP-11
108 or LP-111 mode, which requires support from the transmitter hardware. This is
110 stopped while the state after power-on is LP-00 or LP-000.
118 In the context of CSI-2, the ``.pre_streamon()`` callback is used to transition
119 the transmitter to the LP-11 or LP-111 mode. This also requires powering on the
122 Receiver drivers that do not need explicit LP-11 or LP-111 mode setup are waived