drm/amd/display: Move LTTPR cap read into its own function

[WHY]
We want LTTPR capabilities to be readable from more places than just
retrieve_link_cap
Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@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/core/dc_link_dp.c

@@ -3619,47 +3619,16 @@ static bool dpcd_read_sink_ext_caps(struct dc_link *link)
 	return true;
 }
 
-static bool retrieve_link_cap(struct dc_link *link)
+bool dp_retrieve_lttpr_cap(struct dc_link *link)
 {
-	/* DP_ADAPTER_CAP - DP_DPCD_REV + 1 == 16 and also DP_DSC_BITS_PER_PIXEL_INC - DP_DSC_SUPPORT + 1 == 16,
-	 * which means size 16 will be good for both of those DPCD register block reads
-	 */
-	uint8_t dpcd_data[16];
 	uint8_t lttpr_dpcd_data[6];
-
-	/*Only need to read 1 byte starting from DP_DPRX_FEATURE_ENUMERATION_LIST.
-	 */
-	uint8_t dpcd_dprx_data = '\0';
-	uint8_t dpcd_power_state = '\0';
-
-	struct dp_device_vendor_id sink_id;
-	union down_stream_port_count down_strm_port_count;
-	union edp_configuration_cap edp_config_cap;
-	union dp_downstream_port_present ds_port = { 0 };
-	enum dc_status status = DC_ERROR_UNEXPECTED;
-	uint32_t read_dpcd_retry_cnt = 3;
-	int i;
-	struct dp_sink_hw_fw_revision dp_hw_fw_revision;
-	bool is_lttpr_present = false;
-	const uint32_t post_oui_delay = 30; // 30ms
 	bool vbios_lttpr_enable = false;
 	bool vbios_lttpr_interop = false;
 	struct dc_bios *bios = link->dc->ctx->dc_bios;
+	enum dc_status status = DC_ERROR_UNEXPECTED;
+	bool is_lttpr_present = false;
 
-	memset(dpcd_data, '\0', sizeof(dpcd_data));
 	memset(lttpr_dpcd_data, '\0', sizeof(lttpr_dpcd_data));
-	memset(&down_strm_port_count,
-		'\0', sizeof(union down_stream_port_count));
-	memset(&edp_config_cap, '\0',
-		sizeof(union edp_configuration_cap));
-
-	/* if extended timeout is supported in hardware,
-	 * default to LTTPR timeout (3.2ms) first as a W/A for DP link layer
-	 * CTS 4.2.1.1 regression introduced by CTS specs requirement update.
-	 */
-	dc_link_aux_try_to_configure_timeout(link->ddc,
-			LINK_AUX_DEFAULT_LTTPR_TIMEOUT_PERIOD);
-
 	/* Query BIOS to determine if LTTPR functionality is forced on by system */
 	if (bios->funcs->get_lttpr_caps) {
 		enum bp_result bp_query_result;
@@ -3741,7 +3710,45 @@ static bool retrieve_link_cap(struct dc_link *link)
 		else
 			link->lttpr_mode = LTTPR_MODE_NON_LTTPR;
 	}
+	return is_lttpr_present;
+}
+
+static bool retrieve_link_cap(struct dc_link *link)
+{
+	/* DP_ADAPTER_CAP - DP_DPCD_REV + 1 == 16 and also DP_DSC_BITS_PER_PIXEL_INC - DP_DSC_SUPPORT + 1 == 16,
+	 * which means size 16 will be good for both of those DPCD register block reads
+	 */
+	uint8_t dpcd_data[16];
+	/*Only need to read 1 byte starting from DP_DPRX_FEATURE_ENUMERATION_LIST.
+	 */
+	uint8_t dpcd_dprx_data = '\0';
+	uint8_t dpcd_power_state = '\0';
+
+	struct dp_device_vendor_id sink_id;
+	union down_stream_port_count down_strm_port_count;
+	union edp_configuration_cap edp_config_cap;
+	union dp_downstream_port_present ds_port = { 0 };
+	enum dc_status status = DC_ERROR_UNEXPECTED;
+	uint32_t read_dpcd_retry_cnt = 3;
+	int i;
+	struct dp_sink_hw_fw_revision dp_hw_fw_revision;
+	const uint32_t post_oui_delay = 30; // 30ms
+	bool is_lttpr_present = false;
+
+	memset(dpcd_data, '\0', sizeof(dpcd_data));
+	memset(&down_strm_port_count,
+		'\0', sizeof(union down_stream_port_count));
+	memset(&edp_config_cap, '\0',
+		sizeof(union edp_configuration_cap));
+
+	/* if extended timeout is supported in hardware,
+	 * default to LTTPR timeout (3.2ms) first as a W/A for DP link layer
+	 * CTS 4.2.1.1 regression introduced by CTS specs requirement update.
+	 */
+	dc_link_aux_try_to_configure_timeout(link->ddc,
+			LINK_AUX_DEFAULT_LTTPR_TIMEOUT_PERIOD);
 
+	is_lttpr_present = dp_retrieve_lttpr_cap(link);
 	if (!is_lttpr_present)
 		dc_link_aux_try_to_configure_timeout(link->ddc, LINK_AUX_DEFAULT_TIMEOUT_PERIOD);