drm/amd/display: Read LTTPR ALPM caps during link cap retrieval

[Why]
The latest DP spec requires the DP TX to read DPCD F0000h through F0009h
when detecting LTTPR capabilities for the first time.

[How]
Update LTTPR cap retrieval to read up to F0009h (two more bytes than the
previous F0007h), and store the LTTPR ALPM capabilities.

Reviewed-by: Wenjing Liu <[e-mail]>
Signed-off-by: George Shen <[e-mail]>
Signed-off-by: Roman Li <[e-mail]>
Tested-by: Daniel Wheeler <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

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

···
 	uint8_t raw;
 };
 
+union dp_alpm_lttpr_cap {
+	struct {
+		uint8_t AUX_LESS_ALPM_SUPPORTED	:1;
+		uint8_t RESERVED				:7;
+	} bits;
+	uint8_t raw;
+};
+
 union dp_sink_video_fallback_formats {
 	struct {
 		uint8_t dp_1024x768_60Hz_24bpp_support	:1;
···
 	uint8_t max_ext_timeout;
 	union dp_main_link_channel_coding_lttpr_cap main_link_channel_coding;
 	union dp_128b_132b_supported_lttpr_link_rates supported_128b_132b_rates;
+	union dp_alpm_lttpr_cap alpm;
 	uint8_t aux_rd_interval[MAX_REPEATER_CNT - 1];
 };
 
···
 #endif
 #ifndef DPCD_MAX_UNCOMPRESSED_PIXEL_RATE_CAP
 #define DPCD_MAX_UNCOMPRESSED_PIXEL_RATE_CAP    0x221c
+#endif
+#ifndef DP_LTTPR_ALPM_CAPABILITIES
+#define DP_LTTPR_ALPM_CAPABILITIES              0xF0009
 #endif
 #ifndef DP_REPEATER_CONFIGURATION_AND_STATUS_SIZE
 #define DP_REPEATER_CONFIGURATION_AND_STATUS_SIZE	0x50

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

···
 
 enum dc_status dp_retrieve_lttpr_cap(struct dc_link *link)
 {
-	uint8_t lttpr_dpcd_data[8] = {0};
+	uint8_t lttpr_dpcd_data[10] = {0};
 	enum dc_status status;
 	bool is_lttpr_present;
 
···
 
 	link->dpcd_caps.lttpr_caps.supported_128b_132b_rates.raw =
 			lttpr_dpcd_data[DP_PHY_REPEATER_128B132B_RATES -
+							DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV];
+
+	link->dpcd_caps.lttpr_caps.alpm.raw =
+			lttpr_dpcd_data[DP_LTTPR_ALPM_CAPABILITIES -
 							DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV];
 
 	/* If this chip cap is set, at least one retimer must exist in the chain