This is a note to let you know that I've just added the patch titled
drm/msm/dsi: Prevent signed BPG offsets from bleeding into adjacent bits
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-msm-dsi-prevent-signed-bpg-offsets-from-bleeding.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 7d7a92fea3da5964d6efcb7c89c0294cdeeda739
Author: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx>
Date: Wed Oct 26 20:28:24 2022 +0200
drm/msm/dsi: Prevent signed BPG offsets from bleeding into adjacent bits
[ Upstream commit cc84b66be223d36a3d10d59d68ba647e72db3099 ]
The bpg_offset array contains negative BPG offsets which fill the full 8
bits of a char thanks to two's complement: this however results in those
bits bleeding into the next field when the value is packed into DSC PPS
by the drm_dsc_helper function, which only expects range_bpg_offset to
contain 6-bit wide values. As a consequence random slices appear
corrupted on-screen (tested on a Sony Tama Akatsuki device with sdm845).
Use AND operators to limit these two's complement values to 6 bits,
similar to the AMD and i915 drivers.
Fixes: b9080324d6ca ("drm/msm/dsi: add support for dsc data")
Reviewed-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
Signed-off-by: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx>
Patchwork: https://patchwork.freedesktop.org/patch/508941/
Link: https://lore.kernel.org/r/20221026182824.876933-11-marijn.suijten@xxxxxxxxxxxxxx
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index c229cf6eeb9c..89aadd3b3202 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -1782,7 +1782,11 @@ static int dsi_populate_dsc_params(struct msm_dsi_host *msm_host, struct drm_dsc
for (i = 0; i < DSC_NUM_BUF_RANGES; i++) {
dsc->rc_range_params[i].range_min_qp = min_qp[i];
dsc->rc_range_params[i].range_max_qp = max_qp[i];
- dsc->rc_range_params[i].range_bpg_offset = bpg_offset[i];
+ /*
+ * Range BPG Offset contains two's-complement signed values that fill
+ * 8 bits, yet the registers and DCS PPS field are only 6 bits wide.
+ */
+ dsc->rc_range_params[i].range_bpg_offset = bpg_offset[i] & DSC_RANGE_BPG_OFFSET_MASK;
}
dsc->initial_offset = 6144; /* Not bpp 12 */
