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
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
105 in software, especially when there is no interrupt telling something is
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
133 should not make assumptions either way, but function properly in both