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authorLinus Torvalds <torvalds@linux-foundation.org>2021-09-01 10:34:52 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-09-01 10:34:52 -0700
commit835d31d319d9c8c4eb6cac074643360ba0ecab10 (patch)
tree824dc6286c3f34357de0a0c12d0311eca9a6da8d /Documentation/driver-api
parent0d290223a6c77107b1c3988959e49279a8dafaba (diff)
parent9c3a0f285248899dfa81585bc5d5bc9ebdb8fead (diff)
Merge tag 'media/v5.15-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
Pull media updates from Mauro Carvalho Chehab: - new sensor drivers: imx335, imx412, ov9282 - new IR transmitter driver: meson-ir-tx - handro driver gained support for H.264 for Rockchip VDPU2 - imx gained support for i.MX8MQ - ti-vpe has gained support for other SoC variants - lots of cleanups, fixes, board additions and doc improvements * tag 'media/v5.15-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (195 commits) media: venus: venc: add support for V4L2_CID_MPEG_VIDEO_H264_8X8_TRANSFORM control media: venus: venc: Add support for intra-refresh period media: v4l2-ctrls: Add intra-refresh period control media: docs: ext-ctrls-codec: Document cyclic intra-refresh zero control value media: venus: helper: do not set constrained parameters for UBWC media: venus: venc: Fix potential null pointer dereference on pointer fmt media: venus: hfi: fix return value check in sys_get_prop_image_version() media: tegra-cec: Handle errors of clk_prepare_enable() media: cec-pin: rename timer overrun variables media: TDA1997x: report -ENOLINK after disconnecting HDMI source media: TDA1997x: fix tda1997x_query_dv_timings() return value media: Fix cosmetic error in TDA1997x driver media: v4l2-dv-timings.c: fix wrong condition in two for-loops media: imx: add a driver for i.MX8MQ mipi csi rx phy and controller media: dt-bindings: media: document the nxp,imx8mq-mipi-csi2 receiver phy and controller media: imx: imx7_mipi_csis: convert some switch cases to the default media: imx: imx7-media-csi: Fix buffer return upon stream start failure media: imx: imx7-media-csi: Don't set PIXEL_BIT in CSICR1 media: imx: imx7-media-csi: Set TWO_8BIT_SENSOR for >= 10-bit formats media: dt-bindings: media: nxp,imx7-csi: Add i.MX8MM support ...
Diffstat (limited to 'Documentation/driver-api')
-rw-r--r--Documentation/driver-api/media/camera-sensor.rst45
-rw-r--r--Documentation/driver-api/media/cec-core.rst9
-rw-r--r--Documentation/driver-api/media/csi2.rst94
-rw-r--r--Documentation/driver-api/media/index.rst2
-rw-r--r--Documentation/driver-api/media/tx-rx.rst133
5 files changed, 157 insertions, 126 deletions
diff --git a/Documentation/driver-api/media/camera-sensor.rst b/Documentation/driver-api/media/camera-sensor.rst
index 7160336aa475..c7d4891bd24e 100644
--- a/Documentation/driver-api/media/camera-sensor.rst
+++ b/Documentation/driver-api/media/camera-sensor.rst
@@ -3,10 +3,10 @@
Writing camera sensor drivers
=============================
-CSI-2
------
+CSI-2 and parallel (BT.601 and BT.656) busses
+---------------------------------------------
-Please see what is written on :ref:`MIPI_CSI_2`.
+Please see :ref:`transmitter-receiver`.
Handling clocks
---------------
@@ -26,15 +26,16 @@ user.
ACPI
~~~~
-Read the "clock-frequency" _DSD property to denote the frequency. The driver can
-rely on this frequency being used.
+Read the ``clock-frequency`` _DSD property to denote the frequency. The driver
+can rely on this frequency being used.
Devicetree
~~~~~~~~~~
-The currently preferred way to achieve this is using "assigned-clock-rates"
-property. See Documentation/devicetree/bindings/clock/clock-bindings.txt for
-more information. The driver then gets the frequency using clk_get_rate().
+The currently preferred way to achieve this is using ``assigned-clocks``,
+``assigned-clock-parents`` and ``assigned-clock-rates`` properties. See
+``Documentation/devicetree/bindings/clock/clock-bindings.txt`` for more
+information. The driver then gets the frequency using ``clk_get_rate()``.
This approach has the drawback that there's no guarantee that the frequency
hasn't been modified directly or indirectly by another driver, or supported by
@@ -55,7 +56,7 @@ processing pipeline as one or more sub-devices with different cropping and
scaling configurations. The output size of the device is the result of a series
of cropping and scaling operations from the device's pixel array's size.
-An example of such a driver is the smiapp driver (see drivers/media/i2c/smiapp).
+An example of such a driver is the CCS driver (see ``drivers/media/i2c/ccs``).
Register list based drivers
~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -67,7 +68,7 @@ level are independent. How a driver picks such configuration is based on the
format set on a source pad at the end of the device's internal pipeline.
Most sensor drivers are implemented this way, see e.g.
-drivers/media/i2c/imx319.c for an example.
+``drivers/media/i2c/imx319.c`` for an example.
Frame interval configuration
----------------------------
@@ -94,9 +95,10 @@ large variety of devices beyond camera sensors. Devices that have no analogue
crop, use the full source image size, i.e. pixel array size.
Horizontal and vertical blanking are specified by ``V4L2_CID_HBLANK`` and
-``V4L2_CID_VBLANK``, respectively. The unit of these controls are lines. The
-pixel rate is specified by ``V4L2_CID_PIXEL_RATE`` in the same sub-device. The
-unit of that control is Hz.
+``V4L2_CID_VBLANK``, respectively. The unit of the ``V4L2_CID_HBLANK`` control
+is pixels and the unit of the ``V4L2_CID_VBLANK`` is lines. The pixel rate in
+the sensor's **pixel array** is specified by ``V4L2_CID_PIXEL_RATE`` in the same
+sub-device. The unit of that control is pixels per second.
Register list based drivers need to implement read-only sub-device nodes for the
purpose. Devices that are not register list based need these to configure the
@@ -125,14 +127,14 @@ general, the device must be powered on at least when its registers are being
accessed and when it is streaming.
Existing camera sensor drivers may rely on the old
-:c:type:`v4l2_subdev_core_ops`->s_power() callback for bridge or ISP drivers to
+struct v4l2_subdev_core_ops->s_power() callback for bridge or ISP drivers to
manage their power state. This is however **deprecated**. If you feel you need
to begin calling an s_power from an ISP or a bridge driver, instead please add
runtime PM support to the sensor driver you are using. Likewise, new drivers
should not use s_power.
Please see examples in e.g. ``drivers/media/i2c/ov8856.c`` and
-``drivers/media/i2c/smiapp/smiapp-core.c``. The two drivers work in both ACPI
+``drivers/media/i2c/ccs/ccs-core.c``. The two drivers work in both ACPI
and DT based systems.
Control framework
@@ -149,16 +151,3 @@ used to obtain device's power state after the power state transition:
The function returns a non-zero value if it succeeded getting the power count or
runtime PM was disabled, in either of which cases the driver may proceed to
access the device.
-
-Controls
---------
-
-For camera sensors that are connected to a bus where transmitter and receiver
-require common configuration set by drivers, such as CSI-2 or parallel (BT.601
-or BT.656) bus, the ``V4L2_CID_LINK_FREQ`` control is mandatory on transmitter
-drivers. Receiver drivers can use the ``V4L2_CID_LINK_FREQ`` to query the
-frequency used on the bus.
-
-The transmitter drivers should also implement ``V4L2_CID_PIXEL_RATE`` control in
-order to tell the maximum pixel rate to the receiver. This is required on raw
-camera sensors.
diff --git a/Documentation/driver-api/media/cec-core.rst b/Documentation/driver-api/media/cec-core.rst
index 56345eae9a26..c6194ee81c41 100644
--- a/Documentation/driver-api/media/cec-core.rst
+++ b/Documentation/driver-api/media/cec-core.rst
@@ -130,9 +130,12 @@ To enable/disable the hardware::
int (*adap_enable)(struct cec_adapter *adap, bool enable);
This callback enables or disables the CEC hardware. Enabling the CEC hardware
-means powering it up in a state where no logical addresses are claimed. This
-op assumes that the physical address (adap->phys_addr) is valid when enable is
-true and will not change while the CEC adapter remains enabled. The initial
+means powering it up in a state where no logical addresses are claimed. The
+physical address will always be valid if CEC_CAP_NEEDS_HPD is set. If that
+capability is not set, then the physical address can change while the CEC
+hardware is enabled. CEC drivers should not set CEC_CAP_NEEDS_HPD unless
+the hardware design requires that as this will make it impossible to wake
+up displays that pull the HPD low when in standby mode. The initial
state of the CEC adapter after calling cec_allocate_adapter() is disabled.
Note that adap_enable must return 0 if enable is false.
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.
diff --git a/Documentation/driver-api/media/index.rst b/Documentation/driver-api/media/index.rst
index 813d7db59da7..08e206567408 100644
--- a/Documentation/driver-api/media/index.rst
+++ b/Documentation/driver-api/media/index.rst
@@ -37,7 +37,7 @@ Documentation/userspace-api/media/index.rst
rc-core
mc-core
cec-core
- csi2
+ tx-rx
camera-sensor
drivers/index
diff --git a/Documentation/driver-api/media/tx-rx.rst b/Documentation/driver-api/media/tx-rx.rst
new file mode 100644
index 000000000000..e1e9258dd862
--- /dev/null
+++ b/Documentation/driver-api/media/tx-rx.rst
@@ -0,0 +1,133 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. _transmitter-receiver:
+
+Pixel data transmitter and receiver drivers
+===========================================
+
+V4L2 supports various devices that transmit and receive pixel data. Examples of
+these devices include a camera sensor, a TV tuner and a parallel or a CSI-2
+receiver in an SoC.
+
+Bus types
+---------
+
+The following busses are the most common. This section discusses these two only.
+
+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`: https://www.mipi.org/
+
+Parallel
+^^^^^^^^
+
+`BT.601`_ and `BT.656`_ are the most common parallel busses.
+
+.. _`BT.601`: https://en.wikipedia.org/wiki/Rec._601
+.. _`BT.656`: https://en.wikipedia.org/wiki/ITU-R_BT.656
+
+Transmitter drivers
+-------------------
+
+Transmitter drivers generally need to provide the receiver drivers with the
+configuration of the transmitter. What is required depends on the type of the
+bus. These are common for both busses.
+
+Media bus pixel code
+^^^^^^^^^^^^^^^^^^^^
+
+See :ref:`v4l2-mbus-pixelcode`.
+
+Link frequency
+^^^^^^^^^^^^^^
+
+The :ref:`V4L2_CID_LINK_FREQ <v4l2-cid-link-freq>` control is used to tell the
+receiver the frequency of the bus (i.e. it is not the same as the symbol rate).
+
+``.s_stream()`` callback
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+The struct struct v4l2_subdev_video_ops->s_stream() callback is used by the
+receiver driver to control the transmitter driver's streaming state.
+
+
+CSI-2 transmitter drivers
+-------------------------
+
+Pixel rate
+^^^^^^^^^^
+
+The pixel rate on the bus 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
+ - Data is transferred on both rising and falling edge of the signal.
+ * - bits_per_sample
+ - Number of bits per sample.
+ * - k
+ - 16 for D-PHY and 7 for C-PHY
+
+.. note::
+
+ The pixel rate calculated this way is **not** the same thing as the
+ pixel rate on the camera sensor's pixel array which is indicated by the
+ :ref:`V4L2_CID_PIXEL_RATE <v4l2-cid-pixel-rate>` control.
+
+LP-11 and LP-111 modes
+^^^^^^^^^^^^^^^^^^^^^^
+
+As part of transitioning to high speed mode, a CSI-2 transmitter typically
+briefly sets the bus to LP-11 or LP-111 state, depending on the PHY. This period
+may be as short as 100 µs, during which the receiver observes this state and
+proceeds its own part of high speed mode transition.
+
+Most receivers are capable of autonomously handling this once the software has
+configured them to do so, but there are receivers which require software
+involvement in observing LP-11 or LP-111 state. 100 µs is a brief period to hit
+in software, especially when there is no interrupt telling something is
+happening.
+
+One way to address this is to configure the transmitter side explicitly to LP-11
+or LP-111 mode, which requires support from the transmitter hardware. This is
+not universally available. Many devices return to this state once streaming is
+stopped while the state after power-on is LP-00 or LP-000.
+
+The ``.pre_streamon()`` callback may be used to prepare a transmitter for
+transitioning to streaming state, but not yet start streaming. Similarly, the
+``.post_streamoff()`` callback is used to undo what was done by the
+``.pre_streamon()`` callback. The caller of ``.pre_streamon()`` is thus required
+to call ``.post_streamoff()`` for each successful call of ``.pre_streamon()``.
+
+In the context of CSI-2, the ``.pre_streamon()`` callback is used to transition
+the transmitter to the LP-11 or LP-111 mode. This also requires powering on the
+device, so this should be only done when it is needed.
+
+Receiver drivers that do not need explicit LP-11 or LP-111 mode setup are waived
+from calling the two callbacks.
+
+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.