drm/amd/display: Add support for 6.75 GBps link rate

[Why]
The latest eDP spec version 1.5 defines a new generic link
rate of 6.75 Gbps/Lane, which needs to be supported in the driver.

[How]
Added new element to the dc_link_rate enum
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Artem Grishin <Artem.Grishin@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/dc_dp_types.h

@@ -47,14 +47,15 @@ enum dc_lane_count {
  */
 enum dc_link_rate {
 	LINK_RATE_UNKNOWN = 0,
-	LINK_RATE_LOW = 0x06,		// Rate_1 (RBR)	- 1.62 Gbps/Lane
-	LINK_RATE_RATE_2 = 0x08,	// Rate_2		- 2.16 Gbps/Lane
-	LINK_RATE_RATE_3 = 0x09,	// Rate_3		- 2.43 Gbps/Lane
-	LINK_RATE_HIGH = 0x0A,		// Rate_4 (HBR)	- 2.70 Gbps/Lane
-	LINK_RATE_RBR2 = 0x0C,		// Rate_5 (RBR2)- 3.24 Gbps/Lane
-	LINK_RATE_RATE_6 = 0x10,	// Rate_6		- 4.32 Gbps/Lane
-	LINK_RATE_HIGH2 = 0x14,		// Rate_7 (HBR2)- 5.40 Gbps/Lane
-	LINK_RATE_HIGH3 = 0x1E,		// Rate_8 (HBR3)- 8.10 Gbps/Lane
+	LINK_RATE_LOW = 0x06,		// Rate_1 (RBR)  - 1.62 Gbps/Lane
+	LINK_RATE_RATE_2 = 0x08,	// Rate_2        - 2.16 Gbps/Lane
+	LINK_RATE_RATE_3 = 0x09,	// Rate_3        - 2.43 Gbps/Lane
+	LINK_RATE_HIGH = 0x0A,		// Rate_4 (HBR)  - 2.70 Gbps/Lane
+	LINK_RATE_RBR2 = 0x0C,		// Rate_5 (RBR2) - 3.24 Gbps/Lane
+	LINK_RATE_RATE_6 = 0x10,	// Rate_6        - 4.32 Gbps/Lane
+	LINK_RATE_HIGH2 = 0x14,		// Rate_7 (HBR2) - 5.40 Gbps/Lane
+	LINK_RATE_RATE_8 = 0x19,	// Rate_8        - 6.75 Gbps/Lane
+	LINK_RATE_HIGH3 = 0x1E,		// Rate_9 (HBR3) - 8.10 Gbps/Lane
 	/* Starting from DP2.0 link rate enum directly represents actual
 	 * link rate value in unit of 10 mbps
 	 */

drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c

@@ -203,8 +203,11 @@ static enum dc_link_rate linkRateInKHzToLinkRateMultiplier(uint32_t link_rate_in
 	case 5400000:
 		link_rate = LINK_RATE_HIGH2;	// Rate_7 (HBR2)- 5.40 Gbps/Lane
 		break;
+	case 6750000:
+		link_rate = LINK_RATE_RATE_8;	// Rate_8	- 6.75 Gbps/Lane
+		break;
 	case 8100000:
-		link_rate = LINK_RATE_HIGH3;	// Rate_8 (HBR3)- 8.10 Gbps/Lane
+		link_rate = LINK_RATE_HIGH3;	// Rate_9 (HBR3)- 8.10 Gbps/Lane
 		break;
 	default:
 		link_rate = LINK_RATE_UNKNOWN;

drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training.c

@@ -86,6 +86,9 @@ void dp_log_training_result(
 	case LINK_RATE_HIGH2:
 		link_rate = "HBR2";
 		break;
+	case LINK_RATE_RATE_8:
+		link_rate = "R8";
+		break;
 	case LINK_RATE_HIGH3:
 		link_rate = "HBR3";
 		break;