drm/i915/dsc: Move rc param calculation for native_420

Move rc_param calculation for native_420 into calculate_rc_parameter.
second_line_bpg_offset and second_line_offset_adj are both rc params
and it would be better to have these calculated where all the other
rc parameters are calculated.

--v2
-Add the reason for commit in commit message [Jani]

--v3
-Move nsl_second_line_bpg_offset with the other 420 calculation
in calculate_rc_param [Ankit]

--v4
-Fix comment alignment [Ankit]

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ankit Nautiyal <ankit.k.nautiyal@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/20230705051502.2568245-2-suraj.kandpal@intel.com

Author: surajk8

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

@@ -78,6 +78,28 @@ calculate_rc_params(struct drm_dsc_config *vdsc_cfg)
 	else
 		vdsc_cfg->first_line_bpg_offset = 2 * (vdsc_cfg->slice_height - 1);
 
+	/*
+	 * According to DSC 1.2 spec in Section 4.1 if native_420 is set:
+	 * -second_line_bpg_offset is 12 in general and equal to 2*(slice_height-1) if slice
+	 * height < 8.
+	 * -second_line_offset_adj is 512 as shown by emperical values to yield best chroma
+	 * preservation in second line.
+	 * -nsl_bpg_offset is calculated as second_line_offset/slice_height -1 then rounded
+	 * up to 16 fractional bits, we left shift second line offset by 11 to preserve 11
+	 * fractional bits.
+	 */
+	if (vdsc_cfg->native_420) {
+		if (vdsc_cfg->slice_height >= 8)
+			vdsc_cfg->second_line_bpg_offset = 12;
+		else
+			vdsc_cfg->second_line_bpg_offset =
+				2 * (vdsc_cfg->slice_height - 1);
+
+		vdsc_cfg->second_line_offset_adj = 512;
+		vdsc_cfg->nsl_bpg_offset = DIV_ROUND_UP(vdsc_cfg->second_line_bpg_offset << 11,
+							vdsc_cfg->slice_height - 1);
+	}
+
 	/* Our hw supports only 444 modes as of today */
 	if (bpp >= 12)
 		vdsc_cfg->initial_offset = 2048;
@@ -190,30 +212,12 @@ int intel_dsc_compute_params(struct intel_crtc_state *pipe_config)
 	vdsc_cfg->bits_per_pixel = compressed_bpp << 4;
 
 	/*
-	 * According to DSC 1.2 specs in Section 4.1 if native_420 is set:
-	 * -We need to double the current bpp.
-	 * -second_line_bpg_offset is 12 in general and equal to 2*(slice_height-1) if slice
-	 * height < 8.
-	 * -second_line_offset_adj is 512 as shown by emperical values to yeild best chroma
-	 * preservation in second line.
-	 * -nsl_bpg_offset is calculated as second_line_offset/slice_height -1 then rounded
-	 * up to 16 fractional bits, we left shift second line offset by 11 to preserve 11
-	 * fractional bits.
+	 * According to DSC 1.2 specs in Section 4.1 if native_420 is set
+	 * we need to double the current bpp.
 	 */
-	if (vdsc_cfg->native_420) {
+	if (vdsc_cfg->native_420)
 		vdsc_cfg->bits_per_pixel <<= 1;
 
-		if (vdsc_cfg->slice_height >= 8)
-			vdsc_cfg->second_line_bpg_offset = 12;
-		else
-			vdsc_cfg->second_line_bpg_offset =
-				2 * (vdsc_cfg->slice_height - 1);
-
-		vdsc_cfg->second_line_offset_adj = 512;
-		vdsc_cfg->nsl_bpg_offset = DIV_ROUND_UP(vdsc_cfg->second_line_bpg_offset << 11,
-							vdsc_cfg->slice_height - 1);
-	}
-
 	vdsc_cfg->bits_per_component = pipe_config->pipe_bpp / 3;
 
 	drm_dsc_set_rc_buf_thresh(vdsc_cfg);