drm/amd/display: add dsc policy getter

dc needs to expose its internal dsc policy.
Signed-off-by: Wenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: Nikola Cornij <Nikola.Cornij@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dc_dsc.h

@@ -45,6 +45,14 @@ struct display_stream_compressor {
 	int inst;
 };
 
+struct dc_dsc_policy {
+	bool use_min_slices_h;
+	int max_slices_h; // Maximum available if 0
+	int min_slice_height; // Must not be less than 8
+	uint32_t max_target_bpp;
+	uint32_t min_target_bpp;
+};
+
 bool dc_dsc_parse_dsc_dpcd(const uint8_t *dpcd_dsc_basic_data,
 		const uint8_t *dpcd_dsc_ext_data,
 		struct dsc_dec_dpcd_caps *dsc_sink_caps);
@@ -66,7 +74,7 @@ bool dc_dsc_compute_config(
 		const struct dc_crtc_timing *timing,
 		struct dc_dsc_config *dsc_cfg);
 
-bool dc_dsc_get_bpp_range_for_pixel_encoding(enum dc_pixel_encoding pixel_enc,
-		uint32_t *min_bpp,
-		uint32_t *max_bpp);
+void dc_dsc_get_policy_for_timing(const struct dc_crtc_timing *timing,
+		struct dc_dsc_policy *policy);
+
 #endif

drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c

@@ -27,19 +27,6 @@
 #include <drm/drm_dp_helper.h>
 #include "dc.h"
 
-struct dc_dsc_policy {
-	bool use_min_slices_h;
-	int max_slices_h; // Maximum available if 0
-	int min_sice_height; // Must not be less than 8
-};
-
-const struct dc_dsc_policy dsc_policy = {
-	.use_min_slices_h = true, // DSC Policy: Use minimum number of slices that fits the pixel clock
-	.max_slices_h = 0, // DSC Policy: Use max available slices (in our case 4 for or 8, depending on the mode)
-	.min_sice_height = 108, // DSC Policy: Use slice height recommended by VESA DSC Spreadsheet user guide
-};
-
-
 /* This module's internal functions */
 
 static uint32_t dc_dsc_bandwidth_in_kbps_from_timing(
@@ -370,6 +357,7 @@ static void get_dsc_bandwidth_range(
  *        or if it couldn't be applied based on DSC policy.
  */
 static bool decide_dsc_target_bpp_x16(
+		const struct dc_dsc_policy *policy,
 		const struct dsc_enc_caps *dsc_common_caps,
 		const int target_bandwidth_kbps,
 		const struct dc_crtc_timing *timing,
@@ -377,13 +365,10 @@ static bool decide_dsc_target_bpp_x16(
 {
 	bool should_use_dsc = false;
 	struct dc_dsc_bw_range range;
-	uint32_t min_target_bpp = 0;
-	uint32_t max_target_bpp = 0;
 
 	memset(&range, 0, sizeof(range));
 
-	dc_dsc_get_bpp_range_for_pixel_encoding(timing->pixel_encoding, &min_target_bpp, &max_target_bpp);
-	get_dsc_bandwidth_range(min_target_bpp, max_target_bpp,
+	get_dsc_bandwidth_range(policy->min_target_bpp, policy->max_target_bpp,
 			dsc_common_caps, timing, &range);
 	if (target_bandwidth_kbps >= range.stream_kbps) {
 		/* enough bandwidth without dsc */
@@ -579,9 +564,11 @@ static bool setup_dsc_config(
 	bool is_dsc_possible = false;
 	int pic_height;
 	int slice_height;
+	struct dc_dsc_policy policy;
 
 	memset(dsc_cfg, 0, sizeof(struct dc_dsc_config));
 
+	dc_dsc_get_policy_for_timing(timing, &policy);
 	pic_width = timing->h_addressable + timing->h_border_left + timing->h_border_right;
 	pic_height = timing->v_addressable + timing->v_border_top + timing->v_border_bottom;
 
@@ -597,7 +584,12 @@ static bool setup_dsc_config(
 		goto done;
 
 	if (target_bandwidth_kbps > 0) {
-		is_dsc_possible = decide_dsc_target_bpp_x16(&dsc_common_caps, target_bandwidth_kbps, timing, &target_bpp);
+		is_dsc_possible = decide_dsc_target_bpp_x16(
+				&policy,
+				&dsc_common_caps,
+				target_bandwidth_kbps,
+				timing,
+				&target_bpp);
 		dsc_cfg->bits_per_pixel = target_bpp;
 	}
 	if (!is_dsc_possible)
@@ -699,20 +691,20 @@ static bool setup_dsc_config(
 	if (!is_dsc_possible)
 		goto done;
 
-	if (dsc_policy.use_min_slices_h) {
+	if (policy.use_min_slices_h) {
 		if (min_slices_h > 0)
 			num_slices_h = min_slices_h;
 		else if (max_slices_h > 0) { // Fall back to max slices if min slices is not working out
-			if (dsc_policy.max_slices_h)
-				num_slices_h = min(dsc_policy.max_slices_h, max_slices_h);
+			if (policy.max_slices_h)
+				num_slices_h = min(policy.max_slices_h, max_slices_h);
 			else
 				num_slices_h = max_slices_h;
 		} else
 			is_dsc_possible = false;
 	} else {
 		if (max_slices_h > 0) {
-			if (dsc_policy.max_slices_h)
-				num_slices_h = min(dsc_policy.max_slices_h, max_slices_h);
+			if (policy.max_slices_h)
+				num_slices_h = min(policy.max_slices_h, max_slices_h);
 			else
 				num_slices_h = max_slices_h;
 		} else if (min_slices_h > 0) // Fall back to min slices if max slices is not possible
@@ -734,7 +726,7 @@ static bool setup_dsc_config(
 	// Slice height (i.e. number of slices per column): start with policy and pick the first one that height is divisible by.
 	// For 4:2:0 make sure the slice height is divisible by 2 as well.
 	if (min_slice_height_override == 0)
-		slice_height = min(dsc_policy.min_sice_height, pic_height);
+		slice_height = min(policy.min_slice_height, pic_height);
 	else
 		slice_height = min(min_slice_height_override, pic_height);
 
@@ -905,28 +897,61 @@ bool dc_dsc_compute_config(
 	return is_dsc_possible;
 }
 
-bool dc_dsc_get_bpp_range_for_pixel_encoding(enum dc_pixel_encoding pixel_enc,
-		uint32_t *min_bpp,
-		uint32_t *max_bpp)
+void dc_dsc_get_policy_for_timing(const struct dc_crtc_timing *timing, struct dc_dsc_policy *policy)
 {
-	bool result = true;
+	uint32_t bpc = 0;
+
+	policy->min_target_bpp = 0;
+	policy->max_target_bpp = 0;
+
+	/* DSC Policy: Use minimum number of slices that fits the pixel clock */
+	policy->use_min_slices_h = true;
 
-	switch (pixel_enc) {
+	/* DSC Policy: Use max available slices
+	 * (in our case 4 for or 8, depending on the mode)
+	 */
+	policy->max_slices_h = 0;
+
+	/* DSC Policy: Use slice height recommended
+	 * by VESA DSC Spreadsheet user guide
+	 */
+	policy->min_slice_height = 108;
+
+	/* DSC Policy: follow DP specs with an internal upper limit to 16 bpp
+	 * for better interoperability
+	 */
+	switch (timing->display_color_depth) {
+	case COLOR_DEPTH_888:
+		bpc = 8;
+		break;
+	case COLOR_DEPTH_101010:
+		bpc = 10;
+		break;
+	case COLOR_DEPTH_121212:
+		bpc = 12;
+		break;
+	default:
+		return;
+	}
+	switch (timing->pixel_encoding) {
 	case PIXEL_ENCODING_RGB:
 	case PIXEL_ENCODING_YCBCR444:
-	case PIXEL_ENCODING_YCBCR422:
-		*min_bpp = 8;
-		*max_bpp = 16;
+	case PIXEL_ENCODING_YCBCR422: /* assume no YCbCr422 native support */
+		/* DP specs limits to 8 */
+		policy->min_target_bpp = 8;
+		/* DP specs limits to 3 x bpc */
+		policy->max_target_bpp = 3 * bpc;
 		break;
 	case PIXEL_ENCODING_YCBCR420:
-		*min_bpp = 6;
-		*max_bpp = 16;
+		/* DP specs limits to 6 */
+		policy->min_target_bpp = 6;
+		/* DP specs limits to 1.5 x bpc assume bpc is an even number */
+		policy->max_target_bpp = bpc * 3 / 2;
 		break;
 	default:
-		*min_bpp = 0;
-		*max_bpp = 0;
-		result = false;
+		return;
 	}
-
-	return result;
+	/* internal upper limit to 16 bpp */
+	if (policy->max_target_bpp > 16)
+		policy->max_target_bpp = 16;
 }