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gpu: ipu-v3: image-convert: add some ASCII art to the exposition

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Visualize the scaling and rotation pipeline with some ASCII art
diagrams. Remove the FIXME comment about missing seam prevention.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Steve Longerbeam <slongerbeam@gmail.com>
This commit is contained in:
Philipp Zabel 2018-09-18 11:34:19 +02:00
parent d966e23d61
commit e46279f097
1 changed files with 29 additions and 10 deletions
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39
drivers/gpu/ipu-v3/ipu-image-convert.c
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@ -37,17 +37,36 @@
* when double_buffering boolean is set).
*
* Note that the input frame must be split up into the same number
* of tiles as the output frame.
* of tiles as the output frame:
*
* FIXME: at this point there is no attempt to deal with visible seams
* at the tile boundaries when upscaling. The seams are caused by a reset
* of the bilinear upscale interpolation when starting a new tile. The
* seams are barely visible for small upscale factors, but become
* increasingly visible as the upscale factor gets larger, since more
* interpolated pixels get thrown out at the tile boundaries. A possilble
* fix might be to overlap tiles of different sizes, but this must be done
* while also maintaining the IDMAC dma buffer address alignment and 8x8 IRT
* alignment restrictions of each tile.
* +---------+-----+
* +-----+---+ | A | B |
* | A | B | | | |
* +-----+---+ --> +---------+-----+
* | C | D | | C | D |
* +-----+---+ | | |
* +---------+-----+
*
* Clockwise 90° rotations are handled by first rescaling into a
* reusable temporary tile buffer and then rotating with the 8x8
* block rotator, writing to the correct destination:
*
* +-----+-----+
* | | |
* +-----+---+ +---------+ | C | A |
* | A | B | | A,B, | | | | |
* +-----+---+ --> | C,D | | --> | | |
* | C | D | +---------+ +-----+-----+
* +-----+---+ | D | B |
* | | |
* +-----+-----+
*
* If the 8x8 block rotator is used, horizontal or vertical flipping
* is done during the rotation step, otherwise flipping is done
* during the scaling step.
* With rotation or flipping, tile order changes between input and
* output image. Tiles are numbered row major from top left to bottom
* right for both input and output image.
*/
#define MAX_STRIPES_W 4