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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
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