[PATCH v5 12/16] Documentation: mali-c55: Add Statistics documentation
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Thu May 30 15:43:04 PDT 2024
Hi Dan,
Thank you for the patch.
On Wed, May 29, 2024 at 04:28:54PM +0100, Daniel Scally wrote:
> Add documentation explaining the ability to capture statistics from
> the mali-c55 driver's new V4L2 device, as well as the various tap
> points from which those statistics can be drawn in the ISP's
> processing flow. Additionally add a page detailing the new V4L2
> meta format for the mali-c55 statistics.
>
> Acked-by: Nayden Kanchev <nayden.kanchev at arm.com>
> Co-developed-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> Signed-off-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> Signed-off-by: Daniel Scally <dan.scally at ideasonboard.com>
> ---
> Changes in v5:
>
> - New patch
>
> Documentation/admin-guide/media/mali-c55.rst | 60 ++++++++++++++++++-
> .../userspace-api/media/v4l/meta-formats.rst | 1 +
> .../media/v4l/metafmt-arm-mali-c55.rst | 28 +++++++++
> 3 files changed, 88 insertions(+), 1 deletion(-)
> create mode 100644 Documentation/userspace-api/media/v4l/metafmt-arm-mali-c55.rst
>
> diff --git a/Documentation/admin-guide/media/mali-c55.rst b/Documentation/admin-guide/media/mali-c55.rst
> index cf4176cb1e44..b75437f6e96a 100644
> --- a/Documentation/admin-guide/media/mali-c55.rst
> +++ b/Documentation/admin-guide/media/mali-c55.rst
> @@ -67,10 +67,11 @@ The driver has 4 V4L2 subdevices:
> - `mali_c55 resizer fr`: The Full-Resolution pipe resizer
> - `mali_c55 resizer ds`: The Downscale pipe resizer
>
> -The driver has 2 V4L2 video devices:
> +The driver has 3 V4L2 video devices:
>
> - `mali-c55 fr`: The full-resolution pipe's capture device
> - `mali-c55 ds`: The downscale pipe's capture device
> +- `mali-c55 3a stats`: The 3A statistics capture device
>
> Frame sequences are synchronised across to two capture devices, meaning if one
> pipe is started later than the other the sequence numbers returned in its
> @@ -326,6 +327,63 @@ configured, followed by formats in the appropriate places:
> # Set format on the video device and stream
> yavta -f RGB565 -s 1920x1080 -c10 /dev/video0
>
> +.. _mali-c55-3a-stats:
> +
> +Capturing ISP Statistics
> +========================
> +
> +The ISP is capable of producing statistics for consumption by image processing
> +algorithms running in userspace. These statistics can be captured by queueing
> +buffers to the `mali-c55 3a stats` V4L2 Device whilst the ISP is streaming. Only
> +the :ref:`V4L2_META_FMT_MALI_C55_3A_STATS <v4l2-meta-fmt-mali-c55-3a-stats>`
> +format is supported, so no format-setting need be done:
> +
> +.. code-block:: none
> +
> + # We assume the media graph has been configured to support RGB565 capture
> + # from the mali-c55 fr V4L2 Device, which is at /dev/video0. The statistics
> + # V4L2 device is at /dev/video3
> +
> + yavta -f RGB565 -s 1920x1080 -c32 /dev/video0 && \
> + yavta -c10 -F /dev/video3
> +
> +The layout of the buffer is described by :c:type:`mali_c55_stats_buffer`,
> +but broadly statistics are generated to support three image processing
> +algorithms; AEXP (Auto-Exposure), AWB (Auto-White Balance) and AF (Auto-Focus).
> +These stats can be drawn from various places in the Mali C55 ISP pipeline, known
> +as "tap points". This high-level block diagram is intended to explain where in
> +the processing flow the statistics can be drawn from::
> +
> + +--> AEXP-2 +----> AEXP-1 +--> AF-0
> + | +----> AF-1 |
> + | | |
> + +---------+ | +--------------+ | +--------------+ |
> + | Input +-+-->+ Digital Gain +---+-->+ Black Level +---+---+
> + +---------+ +--------------+ +--------------+ |
> + +-----------------------------------------------------------------+
> + |
> + | +--------------+ +---------+ +----------------+
> + +-->| Sinter Noise +-+ White +--+--->| Lens Shading +--+---------------+
> + | Reduction | | Balance | | | | | |
> + +--------------+ +---------+ | +----------------+ | |
> + +---> AEXP-0 (A) +--> AEXP-0 (B) |
> + +--------------------------------------------------------------------------+
> + |
> + | +----------------+ +--------------+ +----------------+
> + +-->| Tone mapping +-+--->| Demosaicing +->+ Purple Fringe +-+-----------+
> + | | | +--------------+ | Correction | | |
> + +----------------+ +-> AEXP-IRIDIX +----------------+ +---> AWB-0 |
> + +----------------------------------------------------------------------------+
> + | +-------------+ +-------------+
> + +------------------->| Colour +---+--->| Output |
> + | Correction | | | Pipelines |
> + +-------------+ | +-------------+
> + +--> AWB-1
> +
> +At present all statistics are drawn from the 0th tap point for each algorithm;
> +I.E. AEXP statistics from AEXP-0 (A), AWB statistics from AWB-0 and AF
> +statistics from AF-0. In the future this will be configurable.
> +
> References
> ==========
> .. [1] https://git.linuxtv.org/v4l-utils.git/
> diff --git a/Documentation/userspace-api/media/v4l/meta-formats.rst b/Documentation/userspace-api/media/v4l/meta-formats.rst
> index c23aac823d2c..73c05cc35321 100644
> --- a/Documentation/userspace-api/media/v4l/meta-formats.rst
> +++ b/Documentation/userspace-api/media/v4l/meta-formats.rst
> @@ -15,6 +15,7 @@ These formats are used for the :ref:`metadata` interface only.
> metafmt-d4xx
> metafmt-generic
> metafmt-intel-ipu3
> + metafmt-arm-mali-c55
Alphabetical order please.
> metafmt-rkisp1
> metafmt-uvc
> metafmt-vivid
> diff --git a/Documentation/userspace-api/media/v4l/metafmt-arm-mali-c55.rst b/Documentation/userspace-api/media/v4l/metafmt-arm-mali-c55.rst
> new file mode 100644
> index 000000000000..219a5dd42d70
> --- /dev/null
> +++ b/Documentation/userspace-api/media/v4l/metafmt-arm-mali-c55.rst
> @@ -0,0 +1,28 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +.. _v4l2-meta-fmt-mali-c55-3a-stats:
> +
> +****************************************
> +V4L2_META_FMT_MALI_C55_3A_STATS ('C55S')
> +****************************************
> +
> +3A Statistics
> +=============
Missing blank line.
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> +The ISP device collects different statistics over an input bayer frame. Those
> +statistics can be obtained by userspace from the
> +:ref:`mali-c55 3a stats <mali-c55-3a-stats>` metadata capture video node, using
> +the :c:type:`v4l2_meta_format` interface. The buffer contains a single instance
> +of the C structure :c:type:`mali_c55_stats_buffer` defined in
> +``mali-c55-config.h``, so the structure can be obtained from the buffer by:
> +
> +.. code-block:: C
> +
> + struct mali_c55_stats_buffer *stats =
> + (struct mali_c55_stats_buffer *)buf;
> +
> +For details of the statistics see :c:type:`mali_c55_stats_buffer`.
> +
> +Arm Mali-C55 uAPI data types
> +============================
> +
> +.. kernel-doc:: include/uapi/linux/media/arm/mali-c55-config.h
--
Regards,
Laurent Pinchart
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