drm/i915/dsc: Add rc_range_parameter calculation for YCbCr420

Some rc_range_parameter calculations were missed for YCbCr420,
add them to calculate_rc_param()

--v2
-take into account the new formula to get bpp_i

--v4
-Fix range_bpg_offset formula for YCbCr420 bpp <= 16 [Ankit]

--v5
-Fix comment and mention use of DSC C Model [Ankit]

Cc: Vandita Kulkarni <vandita.kulkarni@intel.com>
Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Cc: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230710162456.2736949-1-suraj.kandpal@intel.com

drivers/gpu/drm/i915/display/intel_vdsc.c

@@ -52,23 +52,33 @@ static bool is_pipe_dsc(struct intel_crtc *crtc, enum transcoder cpu_transcoder)
 	return true;
 }
 
+static void
+intel_vdsc_set_min_max_qp(struct drm_dsc_config *vdsc_cfg, int buf,
+			  int bpp)
+{
+	int bpc = vdsc_cfg->bits_per_component;
+
+	/* Read range_minqp and range_max_qp from qp tables */
+	vdsc_cfg->rc_range_params[buf].range_min_qp =
+		intel_lookup_range_min_qp(bpc, buf, bpp, vdsc_cfg->native_420);
+	vdsc_cfg->rc_range_params[buf].range_max_qp =
+		intel_lookup_range_max_qp(bpc, buf, bpp, vdsc_cfg->native_420);
+}
+
+/*
+ * 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
+ * variables. The formula approach may yield slight differences in the derived PPS
+ * parameters from the original parameter sets. These differences are not consequential
+ * to the coding performance because all parameter sets have been shown to produce
+ * visually lossless quality (provides the same PPS values as
+ * DSCParameterValuesVESA V1-2 spreadsheet).
+ */
 static void
 calculate_rc_params(struct drm_dsc_config *vdsc_cfg)
 {
 	int bpc = vdsc_cfg->bits_per_component;
 	int bpp = vdsc_cfg->bits_per_pixel >> 4;
-	static const s8 ofs_und6[] = {
-		0, -2, -2, -4, -6, -6, -8, -8, -8, -10, -10, -12, -12, -12, -12
-	};
-	static const s8 ofs_und8[] = {
-		2, 0, 0, -2, -4, -6, -8, -8, -8, -10, -10, -10, -12, -12, -12
-	};
-	static const s8 ofs_und12[] = {
-		2, 0, 0, -2, -4, -6, -8, -8, -8, -10, -10, -10, -12, -12, -12
-	};
-	static const s8 ofs_und15[] = {
-		10, 8, 6, 4, 2, 0, -2, -4, -6, -8, -10, -10, -12, -12, -12
-	};
 	int qp_bpc_modifier = (bpc - 8) * 2;
 	u32 res, buf_i, bpp_i;
 
@@ -119,33 +129,88 @@ calculate_rc_params(struct drm_dsc_config *vdsc_cfg)
 	vdsc_cfg->rc_quant_incr_limit0 = 11 + qp_bpc_modifier;
 	vdsc_cfg->rc_quant_incr_limit1 = 11 + qp_bpc_modifier;
 
-	bpp_i  = (2 * (bpp - 6));
-	for (buf_i = 0; buf_i < DSC_NUM_BUF_RANGES; buf_i++) {
-		u8 range_bpg_offset;
-
-		/* Read range_minqp and range_max_qp from qp tables */
-		vdsc_cfg->rc_range_params[buf_i].range_min_qp =
-			intel_lookup_range_min_qp(bpc, buf_i, bpp_i, vdsc_cfg->native_420);
-		vdsc_cfg->rc_range_params[buf_i].range_max_qp =
-			intel_lookup_range_max_qp(bpc, buf_i, bpp_i, vdsc_cfg->native_420);
-
-		/* Calculate range_bpg_offset */
-		if (bpp <= 6) {
-			range_bpg_offset = ofs_und6[buf_i];
-		} else if (bpp <= 8) {
-			res = DIV_ROUND_UP(((bpp - 6) * (ofs_und8[buf_i] - ofs_und6[buf_i])), 2);
-			range_bpg_offset = ofs_und6[buf_i] + res;
-		} else if (bpp <= 12) {
-			range_bpg_offset = ofs_und8[buf_i];
-		} else if (bpp <= 15) {
-			res = DIV_ROUND_UP(((bpp - 12) * (ofs_und15[buf_i] - ofs_und12[buf_i])), 3);
-			range_bpg_offset = ofs_und12[buf_i] + res;
-		} else {
-			range_bpg_offset = ofs_und15[buf_i];
+	if (vdsc_cfg->native_420) {
+		static const s8 ofs_und4[] = {
+			2, 0, 0, -2, -4, -6, -8, -8, -8, -10, -10, -12, -12, -12, -12
+		};
+		static const s8 ofs_und5[] = {
+			2, 0, 0, -2, -4, -6, -8, -8, -8, -10, -10, -10, -12, -12, -12
+		};
+		static const s8 ofs_und6[] = {
+			2, 0, 0, -2, -4, -6, -8, -8, -8, -10, -10, -10, -12, -12, -12
+		};
+		static const s8 ofs_und8[] = {
+			10, 8, 6, 4, 2, 0, -2, -4, -6, -8, -10, -10, -12, -12, -12
+		};
+
+		bpp_i  = bpp - 8;
+		for (buf_i = 0; buf_i < DSC_NUM_BUF_RANGES; buf_i++) {
+			u8 range_bpg_offset;
+
+			intel_vdsc_set_min_max_qp(vdsc_cfg, buf_i, bpp_i);
+
+			/* Calculate range_bpg_offset */
+			if (bpp <= 8) {
+				range_bpg_offset = ofs_und4[buf_i];
+			} else if (bpp <= 10) {
+				res = DIV_ROUND_UP(((bpp - 8) *
+						    (ofs_und5[buf_i] - ofs_und4[buf_i])), 2);
+				range_bpg_offset = ofs_und4[buf_i] + res;
+			} else if (bpp <= 12) {
+				res = DIV_ROUND_UP(((bpp - 10) *
+						    (ofs_und6[buf_i] - ofs_und5[buf_i])), 2);
+				range_bpg_offset = ofs_und5[buf_i] + res;
+			} else if (bpp <= 16) {
+				res = DIV_ROUND_UP(((bpp - 12) *
+						    (ofs_und8[buf_i] - ofs_und6[buf_i])), 4);
+				range_bpg_offset = ofs_und6[buf_i] + res;
+			} else {
+				range_bpg_offset = ofs_und8[buf_i];
+			}
+
+			vdsc_cfg->rc_range_params[buf_i].range_bpg_offset =
+				range_bpg_offset & DSC_RANGE_BPG_OFFSET_MASK;
+		}
+	} else {
+		static const s8 ofs_und6[] = {
+			0, -2, -2, -4, -6, -6, -8, -8, -8, -10, -10, -12, -12, -12, -12
+		};
+		static const s8 ofs_und8[] = {
+			2, 0, 0, -2, -4, -6, -8, -8, -8, -10, -10, -10, -12, -12, -12
+		};
+		static const s8 ofs_und12[] = {
+			2, 0, 0, -2, -4, -6, -8, -8, -8, -10, -10, -10, -12, -12, -12
+		};
+		static const s8 ofs_und15[] = {
+			10, 8, 6, 4, 2, 0, -2, -4, -6, -8, -10, -10, -12, -12, -12
+		};
+
+		bpp_i  = (2 * (bpp - 6));
+		for (buf_i = 0; buf_i < DSC_NUM_BUF_RANGES; buf_i++) {
+			u8 range_bpg_offset;
+
+			intel_vdsc_set_min_max_qp(vdsc_cfg, buf_i, bpp_i);
+
+			/* Calculate range_bpg_offset */
+			if (bpp <= 6) {
+				range_bpg_offset = ofs_und6[buf_i];
+			} else if (bpp <= 8) {
+				res = DIV_ROUND_UP(((bpp - 6) *
+						    (ofs_und8[buf_i] - ofs_und6[buf_i])), 2);
+				range_bpg_offset = ofs_und6[buf_i] + res;
+			} else if (bpp <= 12) {
+				range_bpg_offset = ofs_und8[buf_i];
+			} else if (bpp <= 15) {
+				res = DIV_ROUND_UP(((bpp - 12) *
+						    (ofs_und15[buf_i] - ofs_und12[buf_i])), 3);
+				range_bpg_offset = ofs_und12[buf_i] + res;
+			} else {
+				range_bpg_offset = ofs_und15[buf_i];
+			}
+
+			vdsc_cfg->rc_range_params[buf_i].range_bpg_offset =
+				range_bpg_offset & DSC_RANGE_BPG_OFFSET_MASK;
 		}
-
-		vdsc_cfg->rc_range_params[buf_i].range_bpg_offset =
-			range_bpg_offset & DSC_RANGE_BPG_OFFSET_MASK;
 	}
 }