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.za...@pengutronix.de> --- No changes since v3. --- drivers/gpu/ipu-v3/ipu-image-convert.c | 39 +++++++++++++++++++------- 1 file changed, 29 insertions(+), 10 deletions(-) diff --git a/drivers/gpu/ipu-v3/ipu-image-convert.c b/drivers/gpu/ipu-v3/ipu-image-convert.c index b735065fe288..91fe8f1672b4 100644 --- a/drivers/gpu/ipu-v3/ipu-image-convert.c +++ b/drivers/gpu/ipu-v3/ipu-image-convert.c @@ -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 -- 2.19.0
