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author | Linus Torvalds <torvalds@linux-foundation.org> | 2021-09-01 20:34:52 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-09-01 20:34:52 +0300 |
commit | 835d31d319d9c8c4eb6cac074643360ba0ecab10 (patch) | |
tree | 824dc6286c3f34357de0a0c12d0311eca9a6da8d /Documentation/driver-api | |
parent | 0d290223a6c77107b1c3988959e49279a8dafaba (diff) | |
parent | 9c3a0f285248899dfa81585bc5d5bc9ebdb8fead (diff) | |
download | linux-835d31d319d9c8c4eb6cac074643360ba0ecab10.tar.xz |
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.rst | 45 | ||||
-rw-r--r-- | Documentation/driver-api/media/cec-core.rst | 9 | ||||
-rw-r--r-- | Documentation/driver-api/media/csi2.rst | 94 | ||||
-rw-r--r-- | Documentation/driver-api/media/index.rst | 2 | ||||
-rw-r--r-- | Documentation/driver-api/media/tx-rx.rst | 133 |
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. |