drm/amd/display: add dsc stream overhead for dp only

[why]
Based on hardware team recommendation this additional dsc overhead
is only required for DP DSC.

[how]
Add a check for is_dp and only apply the overhead if this flag is set.

Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Reviewed-by: Chris Park <Chris.Park@amd.com>
Acked-by: Wayne Lin <Wayne.Lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link.c

@@ -3489,7 +3489,8 @@ uint32_t dc_bandwidth_in_kbps_from_timing(
 	if (timing->flags.DSC)
 		return dc_dsc_stream_bandwidth_in_kbps(timing,
 				timing->dsc_cfg.bits_per_pixel,
-				timing->dsc_cfg.num_slices_h);
+				timing->dsc_cfg.num_slices_h,
+				timing->dsc_cfg.is_dp);
 #endif
 
 	switch (timing->display_color_depth) {

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

@@ -79,7 +79,7 @@ bool dc_dsc_compute_config(
 		struct dc_dsc_config *dsc_cfg);
 
 uint32_t dc_dsc_stream_bandwidth_in_kbps(const struct dc_crtc_timing *timing,
-		uint32_t bpp_x16, uint32_t num_slices_h);
+		uint32_t bpp_x16, uint32_t num_slices_h, bool is_dp);
 
 void dc_dsc_get_policy_for_timing(const struct dc_crtc_timing *timing,
 		uint32_t max_target_bpp_limit_override_x16,
@@ -89,4 +89,6 @@ void dc_dsc_policy_set_max_target_bpp_limit(uint32_t limit);
 
 void dc_dsc_policy_set_enable_dsc_when_not_needed(bool enable);
 
+void dc_dsc_policy_set_disable_dsc_stream_overhead(bool disable);
+
 #endif

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

@@ -739,6 +739,7 @@ struct dc_dsc_config {
 	uint32_t version_minor; /* DSC minor version. Full version is formed as 1.version_minor. */
 	bool ycbcr422_simple; /* Tell DSC engine to convert YCbCr 4:2:2 to 'YCbCr 4:2:2 simple'. */
 	int32_t rc_buffer_size; /* DSC RC buffer block size in bytes */
+	bool is_dp; /* indicate if DSC is applied based on DP's capability */
 };
 struct dc_crtc_timing {
 	uint32_t h_total;

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

@@ -909,6 +909,7 @@ struct dsc_dec_dpcd_caps {
 	uint32_t branch_overall_throughput_0_mps; /* In MPs */
 	uint32_t branch_overall_throughput_1_mps; /* In MPs */
 	uint32_t branch_max_line_width;
+	bool is_dp;
 };
 
 struct dc_golden_table {

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

@@ -37,6 +37,8 @@ static uint32_t dsc_policy_max_target_bpp_limit = 16;
 /* default DSC policy enables DSC only when needed */
 static bool dsc_policy_enable_dsc_when_not_needed;
 
+static bool dsc_policy_disable_dsc_stream_overhead;
+
 static bool dsc_buff_block_size_from_dpcd(int dpcd_buff_block_size, int *buff_block_size)
 {
 
@@ -250,6 +252,7 @@ static bool intersect_dsc_caps(
 	if (pixel_encoding == PIXEL_ENCODING_YCBCR422 || pixel_encoding == PIXEL_ENCODING_YCBCR420)
 		dsc_common_caps->bpp_increment_div = min(dsc_common_caps->bpp_increment_div, (uint32_t)8);
 
+	dsc_common_caps->is_dp = dsc_sink_caps->is_dp;
 	return true;
 }
 
@@ -260,19 +263,23 @@ static inline uint32_t dsc_div_by_10_round_up(uint32_t value)
 
 static struct fixed31_32 compute_dsc_max_bandwidth_overhead(
 		const struct dc_crtc_timing *timing,
-		const int num_slices_h)
+		const int num_slices_h,
+		const bool is_dp)
 {
 	struct fixed31_32 max_dsc_overhead;
 	struct fixed31_32 refresh_rate;
 
+	if (dsc_policy_disable_dsc_stream_overhead || !is_dp)
+		return dc_fixpt_from_int(0);
+
 	/* use target bpp that can take entire target bandwidth */
 	refresh_rate = dc_fixpt_from_int(timing->pix_clk_100hz);
 	refresh_rate = dc_fixpt_div_int(refresh_rate, timing->h_total);
 	refresh_rate = dc_fixpt_div_int(refresh_rate, timing->v_total);
 	refresh_rate = dc_fixpt_mul_int(refresh_rate, 100);
 
 	max_dsc_overhead = dc_fixpt_from_int(num_slices_h);
-	max_dsc_overhead = dc_fixpt_mul_int(max_dsc_overhead, timing->v_addressable);
+	max_dsc_overhead = dc_fixpt_mul_int(max_dsc_overhead, timing->v_total);
 	max_dsc_overhead = dc_fixpt_mul_int(max_dsc_overhead, 256);
 	max_dsc_overhead = dc_fixpt_div_int(max_dsc_overhead, 1000);
 	max_dsc_overhead = dc_fixpt_mul(max_dsc_overhead, refresh_rate);
@@ -284,14 +291,15 @@ static uint32_t compute_bpp_x16_from_target_bandwidth(
 		const uint32_t bandwidth_in_kbps,
 		const struct dc_crtc_timing *timing,
 		const uint32_t num_slices_h,
-		const uint32_t bpp_increment_div)
+		const uint32_t bpp_increment_div,
+		const bool is_dp)
 {
 	struct fixed31_32 overhead_in_kbps;
 	struct fixed31_32 effective_bandwidth_in_kbps;
 	struct fixed31_32 bpp_x16;
 
 	overhead_in_kbps = compute_dsc_max_bandwidth_overhead(
-				timing, num_slices_h);
+				timing, num_slices_h, is_dp);
 	effective_bandwidth_in_kbps = dc_fixpt_from_int(bandwidth_in_kbps);
 	effective_bandwidth_in_kbps = dc_fixpt_sub(effective_bandwidth_in_kbps,
 			overhead_in_kbps);
@@ -319,19 +327,20 @@ static void get_dsc_bandwidth_range(
 
 	/* max dsc target bpp */
 	range->max_kbps = dc_dsc_stream_bandwidth_in_kbps(timing,
-			max_bpp_x16, num_slices_h);
+			max_bpp_x16, num_slices_h, dsc_caps->is_dp);
 	range->max_target_bpp_x16 = max_bpp_x16;
 	if (range->max_kbps > range->stream_kbps) {
 		/* max dsc target bpp is capped to native bandwidth */
 		range->max_kbps = range->stream_kbps;
 		range->max_target_bpp_x16 = compute_bpp_x16_from_target_bandwidth(
 				range->max_kbps, timing, num_slices_h,
-				dsc_caps->bpp_increment_div);
+				dsc_caps->bpp_increment_div,
+				dsc_caps->is_dp);
 	}
 
 	/* min dsc target bpp */
 	range->min_kbps = dc_dsc_stream_bandwidth_in_kbps(timing,
-			min_bpp_x16, num_slices_h);
+			min_bpp_x16, num_slices_h, dsc_caps->is_dp);
 	range->min_target_bpp_x16 = min_bpp_x16;
 	if (range->min_kbps > range->max_kbps) {
 		/* min dsc target bpp is capped to max dsc bandwidth*/
@@ -378,10 +387,9 @@ static bool decide_dsc_target_bpp_x16(
 	} else if (target_bandwidth_kbps >= range.min_kbps) {
 		/* use target bpp that can take entire target bandwidth */
 		*target_bpp_x16 = compute_bpp_x16_from_target_bandwidth(
-				range.max_kbps, timing, num_slices_h,
-				dsc_common_caps->bpp_increment_div);
-		if (*target_bpp_x16 < range.min_kbps)
-			*target_bpp_x16 = range.min_kbps;
+				target_bandwidth_kbps, timing, num_slices_h,
+				dsc_common_caps->bpp_increment_div,
+				dsc_common_caps->is_dp);
 		should_use_dsc = true;
 	} else {
 		/* not enough bandwidth to fulfill minimum requirement */
@@ -751,6 +759,7 @@ static bool setup_dsc_config(
 		dsc_cfg->block_pred_enable = dsc_common_caps.is_block_pred_supported;
 		dsc_cfg->linebuf_depth = dsc_common_caps.lb_bit_depth;
 		dsc_cfg->version_minor = (dsc_common_caps.dsc_version & 0xf0) >> 4;
+		dsc_cfg->is_dp = dsc_sink_caps->is_dp;
 	}
 
 done:
@@ -861,6 +870,7 @@ bool dc_dsc_parse_dsc_dpcd(const struct dc *dc, const uint8_t *dpcd_dsc_basic_da
 	dsc_sink_caps->branch_max_line_width = dpcd_dsc_branch_decoder_caps[DP_DSC_BRANCH_MAX_LINE_WIDTH - DP_DSC_BRANCH_OVERALL_THROUGHPUT_0] * 320;
 	ASSERT(dsc_sink_caps->branch_max_line_width == 0 || dsc_sink_caps->branch_max_line_width >= 5120);
 
+	dsc_sink_caps->is_dp = true;
 	return true;
 }
 
@@ -921,14 +931,14 @@ bool dc_dsc_compute_config(
 }
 
 uint32_t dc_dsc_stream_bandwidth_in_kbps(const struct dc_crtc_timing *timing,
-		uint32_t bpp_x16, uint32_t num_slices_h)
+		uint32_t bpp_x16, uint32_t num_slices_h, bool is_dp)
 {
 	struct fixed31_32 overhead_in_kbps;
 	struct fixed31_32 bpp;
 	struct fixed31_32 actual_bandwidth_in_kbps;
 
 	overhead_in_kbps = compute_dsc_max_bandwidth_overhead(
-			timing, num_slices_h);
+			timing, num_slices_h, is_dp);
 	bpp = dc_fixpt_from_fraction(bpp_x16, 16);
 	actual_bandwidth_in_kbps = dc_fixpt_from_fraction(timing->pix_clk_100hz, 10);
 	actual_bandwidth_in_kbps = dc_fixpt_mul(actual_bandwidth_in_kbps, bpp);
@@ -1017,3 +1027,8 @@ void dc_dsc_policy_set_enable_dsc_when_not_needed(bool enable)
 {
 	dsc_policy_enable_dsc_when_not_needed = enable;
 }
+
+void dc_dsc_policy_set_disable_dsc_stream_overhead(bool disable)
+{
+	dsc_policy_disable_dsc_stream_overhead = disable;
+}

drivers/gpu/drm/amd/display/dc/inc/hw/dsc.h

@@ -88,6 +88,7 @@ struct dsc_enc_caps {
 	int32_t max_total_throughput_mps; /* Maximum total throughput with all the slices combined */
 	int32_t max_slice_width;
 	uint32_t bpp_increment_div; /* bpp increment divisor, e.g. if 16, it's 1/16th of a bit */
+	bool is_dp;
 };
 
 struct dsc_funcs {