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.kand...@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nauti...@intel.com>
---
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
