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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
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Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.. SPDX-License-Identifier: GPL-2.0
+
+DW100 dewarp driver
+===================
+
+The Vivante DW100 Dewarp Processor IP core found on i.MX8MP SoC applies a
+programmable geometrical transformation on the input image to correct distortion
+introduced by lenses.
+
+The transformation function is exposed by the hardware as a grid map with 16x16
+pixel macroblocks indexed using X, Y vertex coordinates.
+::
+
+ Image width
+ <--------------------------------------->
+
+ ^ .-------.-------.-------.-------.-------.
+ | | 16x16 | | | | |
+ I | | pixel | | | | |
+ m | | block | | | | |
+ a | .-------.-------.-------.-------.-------.
+ g | | | | | | |
+ e | | | | | | |
+ | | | | | | |
+ h | .-------.-------.-------.-------.-------.
+ e | | | | | | |
+ i | | | | | | |
+ g | | | | | | |
+ h | .-------.-------.-------.-------.-------.
+ t | | | | | | |
+ | | | | | | |
+ | | | | | | |
+ v '-------'-------'-------'-------'-------'
+
+ Grid of Image Blocks for Dewarping Map
+
+
+Each x, y coordinate register uses 16 bits to record the coordinate address in
+an unsigned 12.4 fixed point format (UQ12.4).
+::
+
+ .----------------------.--------..----------------------.--------.
+ | 31~20 | 19~16 || 15~4 | 3~0 |
+ | (integer) | (frac) || (integer) | (frac) |
+ '----------------------'--------''----------------------'--------'
+ <-------------------------------><------------------------------->
+ Y coordinate X coordinate
+
+ Remap Register Layout
+
+The dewarping map is set from applications using the
+V4L2_CID_DW100_DEWARPING_16x16_VERTEX_MAP control. The control contains
+an array of u32 values storing (x, y) destination coordinates for each
+vertex of the grid. The x coordinate is stored in the 16 LSBs and the y
+coordinate in the 16 MSBs.
+
+The number of elements in the array must match the image size:
+
+.. code-block:: C
+
+ elems = (DIV_ROUND_UP(width, 16) + 1) * (DIV_ROUND_UP(height, 16) + 1);
+
+If the control has not been set by the application, the driver uses an identity
+map.
+
+More details on the DW100 hardware operations can be found in
+*chapter 13.15 DeWarp* of IMX8MP_ reference manual.
+
+The Vivante DW100 m2m driver implements the following driver-specific control:
+
+``V4L2_CID_DW100_DEWARPING_16x16_VERTEX_MAP (__u32 array)``
+ Specifies to DW100 driver its dewarping map (aka LUT) blob as described in
+ *chapter 13.15.2.3 Dewarping Remap* of IMX8MP_ reference manual as an U32
+ dynamic array. The image is divided into many small 16x16 blocks. If the
+ width/height of the image is not divisible by 16, the size of the
+ rightmost/bottommost block is the remainder. The dewarping map only saves
+ the vertex coordinates of the block. The dewarping grid map is comprised of
+ vertex coordinates for x and y. Each x, y coordinate register uses 16 bits
+ (UQ12.4) to record the coordinate address, with the Y coordinate in the
+ upper bits and X in the lower bits. The driver modifies the dimensions of
+ this control when the sink format is changed, to reflect the new input
+ resolution.
+
+.. _IMX8MP: https://www.nxp.com/webapp/Download?colCode=IMX8MPRM