Documentation: media: mali-c55: Document the mali-c55 parameter setting

Document the mali-c55 parameter setting by expanding the relevant
pages in both admin-guide/ and userspace-api/.

Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Nayden Kanchev  <nayden.kanchev@arm.com>
Co-developed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

Author: djrscally

Documentation/admin-guide/media/mali-c55.rst

@@ -387,9 +387,24 @@ the processing flow the statistics can be drawn from::
                        +-------------+   |    +-------------+
                                          +-->  AWB-1
 
-At present all statistics are drawn from the 0th tap point for each algorithm;
+By default 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.
+statistics from AF-0. This is configurable for AEXP and AWB statsistics through
+programming the ISP's parameters.
+
+.. _mali-c55-3a-params:
+
+Programming ISP Parameters
+==========================
+
+The ISP can be programmed with various parameters from userspace to apply to the
+hardware before and during video stream. This allows userspace to dynamically
+change values such as black level, white balance and lens shading gains and so
+on.
+
+The buffer format and how to populate it are described by the
+:ref:`V4L2_META_FMT_MALI_C55_PARAMS <v4l2-meta-fmt-mali-c55-params>` format,
+which should be set as the data format for the `mali-c55 3a params` video node.
 
 References
 ==========

Documentation/userspace-api/media/v4l/metafmt-arm-mali-c55.rst

@@ -1,10 +1,11 @@
 .. SPDX-License-Identifier: GPL-2.0
 
+.. _v4l2-meta-fmt-mali-c55-params:
 .. _v4l2-meta-fmt-mali-c55-stats:
 
-*************************************
-V4L2_META_FMT_MALI_C55_STATS ('C55S')
-*************************************
+*****************************************************************************
+V4L2_META_FMT_MALI_C55_STATS ('C55S'), V4L2_META_FMT_MALI_C55_PARAMS ('C55P')
+*****************************************************************************
 
 3A Statistics
 =============
@@ -23,6 +24,60 @@ of the C structure :c:type:`mali_c55_stats_buffer` defined in
 
 For details of the statistics see :c:type:`mali_c55_stats_buffer`.
 
+Configuration Parameters
+========================
+
+The configuration parameters are passed to the :ref:`mali-c55 3a params
+<mali-c55-3a-params>` metadata output video node, using the
+:c:type:`v4l2_meta_format` interface. Rather than a single struct containing
+sub-structs for each configurable area of the ISP, parameters for the Mali-C55
+use the v4l2-isp parameters system, through which groups of parameters are
+defined as distinct structs or "blocks" which may be added to the data member of
+:c:type:`v4l2_isp_params_buffer`. Userspace is responsible for populating the
+data member with the blocks that need to be configured by the driver.  Each
+block-specific struct embeds :c:type:`v4l2_isp_params_block_header` as its first
+member and userspace must populate the type member with a value from
+:c:type:`mali_c55_param_block_type`.
+
+.. code-block:: c
+
+	struct v4l2_isp_params_buffer *params =
+		(struct v4l2_isp_params_buffer *)buffer;
+
+	params->version = MALI_C55_PARAM_BUFFER_V1;
+	params->data_size = 0;
+
+	void *data = (void *)params->data;
+
+	struct mali_c55_params_awb_gains *gains =
+		(struct mali_c55_params_awb_gains *)data;
+
+	gains->header.type = MALI_C55_PARAM_BLOCK_AWB_GAINS;
+	gains->header.flags |= V4L2_ISP_PARAMS_FL_BLOCK_ENABLE;
+	gains->header.size = sizeof(struct mali_c55_params_awb_gains);
+
+	gains->gain00 = 256;
+	gains->gain00 = 256;
+	gains->gain00 = 256;
+	gains->gain00 = 256;
+
+	data += sizeof(struct mali_c55_params_awb_gains);
+	params->data_size += sizeof(struct mali_c55_params_awb_gains);
+
+	struct mali_c55_params_sensor_off_preshading *blc =
+		(struct mali_c55_params_sensor_off_preshading *)data;
+
+	blc->header.type = MALI_C55_PARAM_BLOCK_SENSOR_OFFS;
+	blc->header.flags |= V4L2_ISP_PARAMS_FL_BLOCK_ENABLE;
+	blc->header.size = sizeof(struct mali_c55_params_sensor_off_preshading);
+
+	blc->chan00 = 51200;
+	blc->chan01 = 51200;
+	blc->chan10 = 51200;
+	blc->chan11 = 51200;
+
+	params->data_size += sizeof(struct mali_c55_params_sensor_off_preshading);
+
 Arm Mali-C55 uAPI data types
 ============================