driver-api/media/tx-rx.rst

1 .. SPDX-License-Identifier: GPL-2.0
3 .. _transmitter-receiver:
10 CSI-2 receiver in an SoC.
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/
32 .. _`BT.656`: https://en.wikipedia.org/wiki/ITU-R_BT.656
35 -------------------
44 See :ref:`v4l2-mbus-pixelcode`.
49 The :ref:`V4L2_CID_LINK_FREQ <v4l2-cid-link-freq>` control is used to tell the
55 The struct struct v4l2_subdev_video_ops->s_stream() callback is used by the
59 CSI-2 transmitter drivers
60 -------------------------
71 .. list-table:: variables in pixel rate calculation
72    :header-rows: 1
74    * - variable or constant
75      - description
76    * - link_freq
77      - The value of the ``V4L2_CID_LINK_FREQ`` integer64 menu item.
78    * - nr_of_lanes
79      - Number of data lanes used on the CSI-2 link. This can
81    * - 2
82      - Data is transferred on both rising and falling edge of the signal.
83    * - bits_per_sample
84      - Number of bits per sample.
85    * - k
86      - 16 for D-PHY and 7 for C-PHY
92 	:ref:`V4L2_CID_PIXEL_RATE <v4l2-cid-pixel-rate>` control.
94 LP-11 and LP-111 states
97 As part of transitioning to high speed mode, a CSI-2 transmitter typically
98 briefly sets the bus to LP-11 or LP-111 state, depending on the PHY. This period
104 involvement in observing LP-11 or LP-111 state. 100 µs is a brief period to hit
108 One way to address this is to configure the transmitter side explicitly to LP-11
109 or LP-111 state, which requires support from the transmitter hardware. This is
111 stopped while the state after power-on is LP-00 or LP-000.
119 In the context of CSI-2, the ``.pre_streamon()`` callback is used to transition
120 the transmitter to the LP-11 or LP-111 state. This also requires powering on the
123 Receiver drivers that do not need explicit LP-11 or LP-111 state setup are