drm/amd/display: Read DPCD to obtain eDP capability information.

[Why & How]
Extend to read eDP general capability 2 in detect_edp_sink_caps().

Reviewed-by: Robin Chen <robin.chen@amd.com>
Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: Allen Li <wei-guang.li@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Allen Li

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

@@ -1284,6 +1284,7 @@ struct dpcd_caps {
 	union dp_receive_port0_cap receive_port0_cap;
 	/* Indicates the number of SST links supported by MSO (Multi-Stream Output) */
 	uint8_t mso_cap_sst_links_supported;
+	uint8_t dp_edp_general_cap_2;
 };
 
 union dpcd_sink_ext_caps {

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

@@ -2195,6 +2195,12 @@ void detect_edp_sink_caps(struct dc_link *link)
 			DP_EDP_MSO_LINK_CAPABILITIES,
 			(uint8_t *)&link->dpcd_caps.mso_cap_sst_links_supported,
 			sizeof(link->dpcd_caps.mso_cap_sst_links_supported));
+	/*
+	 * Read eDP general capability 2
+	 */
+	core_link_read_dpcd(link, DP_EDP_GENERAL_CAP_2,
+			(uint8_t *)&link->dpcd_caps.dp_edp_general_cap_2,
+			sizeof(link->dpcd_caps.dp_edp_general_cap_2));
 }
 
 bool dp_get_max_link_enc_cap(const struct dc_link *link, struct dc_link_settings *max_link_enc_cap)