On checking DSC1.1 Errata and DSC 1.2 spec the current formula we were using was incorrect to calculate first_line_bpg_offset. The new fixed formula is derived from C model. --v2 -Use clamp function in linux/minmax.h [Ankit] --v3 -remove linux/minmax.h header Signed-off-by: Suraj Kandpal <suraj.kandpal@xxxxxxxxx> Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx> --- drivers/gpu/drm/i915/display/intel_vdsc.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_vdsc.c b/drivers/gpu/drm/i915/display/intel_vdsc.c index 9d76c2756784..e4c395b4dc46 100644 --- a/drivers/gpu/drm/i915/display/intel_vdsc.c +++ b/drivers/gpu/drm/i915/display/intel_vdsc.c @@ -80,13 +80,19 @@ calculate_rc_params(struct drm_dsc_config *vdsc_cfg) int bpc = vdsc_cfg->bits_per_component; int bpp = vdsc_cfg->bits_per_pixel >> 4; int qp_bpc_modifier = (bpc - 8) * 2; + int uncompressed_bpg_rate; + int first_line_bpg_offset; u32 res, buf_i, bpp_i; if (vdsc_cfg->slice_height >= 8) - vdsc_cfg->first_line_bpg_offset = - 12 + DIV_ROUND_UP((9 * min(34, vdsc_cfg->slice_height - 8)), 100); + first_line_bpg_offset = + 12 + (9 * min(34, vdsc_cfg->slice_height - 8)) / 100; else - vdsc_cfg->first_line_bpg_offset = 2 * (vdsc_cfg->slice_height - 1); + first_line_bpg_offset = 2 * (vdsc_cfg->slice_height - 1); + + uncompressed_bpg_rate = (3 * bpc + (vdsc_cfg->convert_rgb ? 0 : 2)) * 3; + vdsc_cfg->first_line_bpg_offset = clamp(first_line_bpg_offset, 0, + uncompressed_bpg_rate - 3 * bpp); /* * According to DSC 1.2 spec in Section 4.1 if native_420 is set: -- 2.25.1
