On 8/3/2023 9:32 PM, Suraj Kandpal wrote:
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.
Signed-off-by: Suraj Kandpal <suraj.kandpal@xxxxxxxxx>
---
drivers/gpu/drm/i915/display/intel_vdsc.c | 15 ++++++++++++---
1 file changed, 12 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..a344c6ab8767 100644
--- a/drivers/gpu/drm/i915/display/intel_vdsc.c
+++ b/drivers/gpu/drm/i915/display/intel_vdsc.c
@@ -65,6 +65,9 @@ intel_vdsc_set_min_max_qp(struct drm_dsc_config *vdsc_cfg, int buf,
intel_lookup_range_max_qp(bpc, buf, bpp, vdsc_cfg->native_420);
}
+#define CLAMP_TO(val, _min, _max) \
+ max(_min, min(val, _max))
lets use clamp(), already defined in linux/minmax.h
With that fixed, this is:
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>
+
/*
* We are using the method provided in DSC 1.2a C-Model in codec_main.c
* Above method use a common formula to derive values for any combination of DSC
@@ -80,13 +83,19 @@ 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_TO(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:
