drm/amd/display: use proper formula to calculate bandwidth from timing

[why]
The existing calculation uses a wrong formula to
calculate bandwidth from timing.

[how]
Expose the existing proper function that calculates the bandwidth,
so dc_link can use it to calculate timing bandwidth correctly.
Signed-off-by: NWenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: NJun Lei <Jun.Lei@amd.com>
Acked-by: NLeo Li <sunpeng.li@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

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

@@ -2321,7 +2321,7 @@ static struct fixed31_32 get_pbn_from_timing(struct pipe_ctx *pipe_ctx)
 	uint32_t denominator;
 
 	bpc = get_color_depth(pipe_ctx->stream_res.pix_clk_params.color_depth);
-	kbps = pipe_ctx->stream_res.pix_clk_params.requested_pix_clk_100hz / 10 * bpc * 3;
+	kbps = dc_bandwidth_in_kbps_from_timing(&pipe_ctx->stream->timing);
 
 	/*
 	 * margin 5300ppm + 300ppm ~ 0.6% as per spec, factor is 1.006
@@ -2736,3 +2736,49 @@ void dc_link_enable_hpd_filter(struct dc_link *link, bool enable)
 	}
 }
 
+uint32_t dc_bandwidth_in_kbps_from_timing(
+	const struct dc_crtc_timing *timing)
+{
+	uint32_t bits_per_channel = 0;
+	uint32_t kbps;
+
+	switch (timing->display_color_depth) {
+	case COLOR_DEPTH_666:
+		bits_per_channel = 6;
+		break;
+	case COLOR_DEPTH_888:
+		bits_per_channel = 8;
+		break;
+	case COLOR_DEPTH_101010:
+		bits_per_channel = 10;
+		break;
+	case COLOR_DEPTH_121212:
+		bits_per_channel = 12;
+		break;
+	case COLOR_DEPTH_141414:
+		bits_per_channel = 14;
+		break;
+	case COLOR_DEPTH_161616:
+		bits_per_channel = 16;
+		break;
+	default:
+		break;
+	}
+
+	ASSERT(bits_per_channel != 0);
+
+	kbps = timing->pix_clk_100hz / 10;
+	kbps *= bits_per_channel;
+
+	if (timing->flags.Y_ONLY != 1) {
+		/*Only YOnly make reduce bandwidth by 1/3 compares to RGB*/
+		kbps *= 3;
+		if (timing->pixel_encoding == PIXEL_ENCODING_YCBCR420)
+			kbps /= 2;
+		else if (timing->pixel_encoding == PIXEL_ENCODING_YCBCR422)
+			kbps = kbps * 2 / 3;
+	}
+
+	return kbps;
+
+}

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

@@ -1533,53 +1533,6 @@ static bool decide_fallback_link_setting(
 	return true;
 }
 
-static uint32_t bandwidth_in_kbps_from_timing(
-	const struct dc_crtc_timing *timing)
-{
-	uint32_t bits_per_channel = 0;
-	uint32_t kbps;
-
-	switch (timing->display_color_depth) {
-	case COLOR_DEPTH_666:
-		bits_per_channel = 6;
-		break;
-	case COLOR_DEPTH_888:
-		bits_per_channel = 8;
-		break;
-	case COLOR_DEPTH_101010:
-		bits_per_channel = 10;
-		break;
-	case COLOR_DEPTH_121212:
-		bits_per_channel = 12;
-		break;
-	case COLOR_DEPTH_141414:
-		bits_per_channel = 14;
-		break;
-	case COLOR_DEPTH_161616:
-		bits_per_channel = 16;
-		break;
-	default:
-		break;
-	}
-
-	ASSERT(bits_per_channel != 0);
-
-	kbps = timing->pix_clk_100hz / 10;
-	kbps *= bits_per_channel;
-
-	if (timing->flags.Y_ONLY != 1) {
-		/*Only YOnly make reduce bandwidth by 1/3 compares to RGB*/
-		kbps *= 3;
-		if (timing->pixel_encoding == PIXEL_ENCODING_YCBCR420)
-			kbps /= 2;
-		else if (timing->pixel_encoding == PIXEL_ENCODING_YCBCR422)
-			kbps = kbps * 2 / 3;
-	}
-
-	return kbps;
-
-}
-
 static uint32_t bandwidth_in_kbps_from_link_settings(
 	const struct dc_link_settings *link_setting)
 {
@@ -1620,7 +1573,7 @@ bool dp_validate_mode_timing(
 		link_setting = &link->verified_link_cap;
 	*/
 
-	req_bw = bandwidth_in_kbps_from_timing(timing);
+	req_bw = dc_bandwidth_in_kbps_from_timing(timing);
 	max_bw = bandwidth_in_kbps_from_link_settings(link_setting);
 
 	if (req_bw <= max_bw) {
@@ -1739,7 +1692,7 @@ void decide_link_settings(struct dc_stream_state *stream,
 	struct dc_link *link;
 	uint32_t req_bw;
 
-	req_bw = bandwidth_in_kbps_from_timing(&stream->timing);
+	req_bw = dc_bandwidth_in_kbps_from_timing(&stream->timing);
 
 	link = stream->link;
 

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

@@ -252,4 +252,6 @@ bool dc_submit_i2c(
 		uint32_t link_index,
 		struct i2c_command *cmd);
 
+uint32_t dc_bandwidth_in_kbps_from_timing(
+	const struct dc_crtc_timing *timing);
 #endif /* DC_LINK_H_ */