lkml.org 
[lkml]   [2022]   [Oct]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v3 10/10] drm/msm/dsi: Prevent signed BPG offsets from bleeding into adjacent bits
From


On 10/9/2022 11:53 AM, Marijn Suijten wrote:
> 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")
> Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
> ---
> drivers/gpu/drm/msm/dsi/dsi_host.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index 46032c576a59..c5c2d70ac27d 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -1804,7 +1804,11 @@ 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 */

\
 
 \ /
  Last update: 2022-10-13 01:26    [W:0.160 / U:1.116 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site