drm/amd/display: Calculate link bandwidth in a common function

[why]
Currently link bandwidth is calculated in two places, using the same
formula. They should be unified into calling one function.

[how]
Replace all implementations of link bandwidth calculation with a call
to a function.

Signed-off-by: Nikola Cornij <nikola.cornij@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/core/dc.c

@@ -584,6 +584,19 @@ void dc_link_set_test_pattern(struct dc_link *link,
 			cust_pattern_size);
 }
 
+uint32_t dc_link_bandwidth_kbps(
+	const struct dc_link *link,
+	const struct dc_link_settings *link_setting)
+{
+	uint32_t link_bw_kbps = link_setting->link_rate * LINK_RATE_REF_FREQ_IN_KHZ; /* bytes per sec */
+
+	link_bw_kbps *= 8;   /* 8 bits per byte*/
+	link_bw_kbps *= link_setting->lane_count;
+
+	return link_bw_kbps;
+
+}
+
 static void destruct(struct dc *dc)
 {
 	dc_release_state(dc->current_state);

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

@@ -58,7 +58,6 @@
  ******************************************************************************/
 
 enum {
-	LINK_RATE_REF_FREQ_IN_MHZ = 27,
 	PEAK_FACTOR_X1000 = 1006,
 	/*
 	* Some receivers fail to train on first try and are good
@@ -2289,14 +2288,13 @@ void core_link_resume(struct dc_link *link)
 
 static struct fixed31_32 get_pbn_per_slot(struct dc_stream_state *stream)
 {
-	struct dc_link_settings *link_settings =
-			&stream->link->cur_link_settings;
-	uint32_t link_rate_in_mbps =
-			link_settings->link_rate * LINK_RATE_REF_FREQ_IN_MHZ;
-	struct fixed31_32 mbps = dc_fixpt_from_int(
-			link_rate_in_mbps * link_settings->lane_count);
-
-	return dc_fixpt_div_int(mbps, 54);
+	struct fixed31_32 mbytes_per_sec;
+	uint32_t link_rate_in_mbytes_per_sec = dc_link_bandwidth_kbps(stream->link, &stream->link->cur_link_settings);
+	link_rate_in_mbytes_per_sec /= 8000; /* Kbits to MBytes */
+
+	mbytes_per_sec = dc_fixpt_from_int(link_rate_in_mbytes_per_sec);
+
+	return dc_fixpt_div_int(mbytes_per_sec, 54);
 }
 
 static int get_color_depth(enum dc_color_depth color_depth)

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

@@ -1533,22 +1533,6 @@ static bool decide_fallback_link_setting(
 	return true;
 }
 
-static uint32_t bandwidth_in_kbps_from_link_settings(
-	const struct dc_link_settings *link_setting)
-{
-	uint32_t link_rate_in_kbps = link_setting->link_rate *
-		LINK_RATE_REF_FREQ_IN_KHZ;
-
-	uint32_t lane_count  = link_setting->lane_count;
-	uint32_t kbps = link_rate_in_kbps;
-
-	kbps *= lane_count;
-	kbps *= 8;   /* 8 bits per byte*/
-
-	return kbps;
-
-}
-
 bool dp_validate_mode_timing(
 	struct dc_link *link,
 	const struct dc_crtc_timing *timing)
@@ -1574,7 +1558,7 @@ bool dp_validate_mode_timing(
 	*/
 
 	req_bw = dc_bandwidth_in_kbps_from_timing(timing);
-	max_bw = bandwidth_in_kbps_from_link_settings(link_setting);
+	max_bw = dc_link_bandwidth_kbps(link, link_setting);
 
 	if (req_bw <= max_bw) {
 		/* remember the biggest mode here, during
@@ -1609,7 +1593,8 @@ static bool decide_dp_link_settings(struct dc_link *link, struct dc_link_setting
 	 */
 	while (current_link_setting.link_rate <=
 			link->verified_link_cap.link_rate) {
-		link_bw = bandwidth_in_kbps_from_link_settings(
+		link_bw = dc_link_bandwidth_kbps(
+				link,
 				&current_link_setting);
 		if (req_bw <= link_bw) {
 			*link_setting = current_link_setting;
@@ -1660,7 +1645,8 @@ static bool decide_edp_link_settings(struct dc_link *link, struct dc_link_settin
 	 */
 	while (current_link_setting.link_rate <=
 			link->verified_link_cap.link_rate) {
-		link_bw = bandwidth_in_kbps_from_link_settings(
+		link_bw = dc_link_bandwidth_kbps(
+				link,
 				&current_link_setting);
 		if (req_bw <= link_bw) {
 			*link_setting = current_link_setting;

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

@@ -246,6 +246,9 @@ void dc_link_set_test_pattern(struct dc_link *link,
 			const struct link_training_settings *p_link_settings,
 			const unsigned char *p_custom_pattern,
 			unsigned int cust_pattern_size);
+uint32_t dc_link_bandwidth_kbps(
+	const struct dc_link *link,
+	const struct dc_link_settings *link_setting);
 
 bool dc_submit_i2c(
 		struct dc *dc,