media: hantro: Write quantization table registers in increasing addresses order

Luma and chroma qtables need to be written into two 16-register blocks,
each table consisting of 64 bytes total. The blocks are contiguous and
start at offset 0 for luma and at offset 0x40 for chroma.

The seemingly innocent optimization of writing the two blocks using one
loop causes side effects which result in improper values of quantization
tables being used by the hardware during encoding. Visually this results
in macroblocking artifacts around contrasting edges in encoded images. The
artifacts look like horizontally flipped shadows of the said edges.
Changing the write operations to non-relaxed variant doesn't help.

This patch removes this premature optimization and after this change the
macroblocking artifacts around contrasting edges are gone.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Tested-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/staging/media/hantro/hantro_h1_jpeg_enc.c b/drivers/staging/media/hantro/hantro_h1_jpeg_enc.c
index f62ab96078c6..b22418436823 100644
--- a/drivers/staging/media/hantro/hantro_h1_jpeg_enc.c
+++ b/drivers/staging/media/hantro/hantro_h1_jpeg_enc.c
@@ -73,10 +73,16 @@ hantro_h1_jpeg_enc_set_qtable(struct hantro_dev *vpu,
 	luma_qtable_p = (__be32 *)luma_qtable;
 	chroma_qtable_p = (__be32 *)chroma_qtable;
 
+	/*
+	 * Quantization table registers must be written in contiguous blocks.
+	 * DO NOT collapse the below two "for" loops into one.
+	 */
 	for (i = 0; i < H1_JPEG_QUANT_TABLE_COUNT; i++) {
 		reg = get_unaligned_be32(&luma_qtable_p[i]);
 		vepu_write_relaxed(vpu, reg, H1_REG_JPEG_LUMA_QUAT(i));
+	}
 
+	for (i = 0; i < H1_JPEG_QUANT_TABLE_COUNT; i++) {
 		reg = get_unaligned_be32(&chroma_qtable_p[i]);
 		vepu_write_relaxed(vpu, reg, H1_REG_JPEG_CHROMA_QUAT(i));
 	}