drm/amd/display: DP link layer test 4.2.1.1 fix due to specs update

[why]
DP link layer CTS specs updated to change the test parameters in test
4.2.1.1.
Before it requires source to delay 400us on aux no reply.
With the specs updates Errata5, it requires source to delay 3.2ms
(based on LTTPR aux timeout)
This causes our test to fail after updating with the latest test
equipment firmware.

[how]
the change is to allow LTTPR 3.2ms aux timeout delay by default.
And only set to 400us if LTTPR is not present.
Before this piece of logic is interwined with LTTPR support.
Now we will default to 3.2ms aux timeout even if LTTPR support is not
enabled by driver.
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -691,10 +691,9 @@ static bool detect_dp(struct dc_link *link,
 	if (sink_caps->transaction_type == DDC_TRANSACTION_TYPE_I2C_OVER_AUX) {
 		sink_caps->signal = SIGNAL_TYPE_DISPLAY_PORT;
 
-		dpcd_set_source_specific_data(link);
-
 		if (!detect_dp_sink_caps(link))
 			return false;
+		dpcd_set_source_specific_data(link);
 
 		if (is_mst_supported(link)) {
 			sink_caps->signal = SIGNAL_TYPE_DISPLAY_PORT_MST;

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

@@ -648,16 +648,17 @@ bool dc_link_aux_transfer_with_retries(struct ddc_service *ddc,
 }
 
 
-uint32_t dc_link_aux_configure_timeout(struct ddc_service *ddc,
+bool dc_link_aux_try_to_configure_timeout(struct ddc_service *ddc,
 		uint32_t timeout)
 {
-	uint32_t prev_timeout = 0;
+	bool result = false;
 	struct ddc *ddc_pin = ddc->ddc_pin;
 
-	if (ddc->ctx->dc->res_pool->engines[ddc_pin->pin_data->en]->funcs->configure_timeout)
-		prev_timeout =
+	if (ddc->ctx->dc->res_pool->engines[ddc_pin->pin_data->en]->funcs->configure_timeout) {
 		ddc->ctx->dc->res_pool->engines[ddc_pin->pin_data->en]->funcs->configure_timeout(ddc, timeout);
-	return prev_timeout;
+		result = true;
+	}
+	return result;
 }
 
 /*test only function*/

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

@@ -245,7 +245,7 @@ static uint8_t dc_dp_initialize_scrambling_data_symbols(
 
 static inline bool is_repeater(struct dc_link *link, uint32_t offset)
 {
-	return (!link->is_lttpr_mode_transparent && offset != 0);
+	return (link->lttpr_non_transparent_mode && offset != 0);
 }
 
 static void dpcd_set_lt_pattern_and_lane_settings(
@@ -1038,7 +1038,7 @@ static enum link_training_result perform_clock_recovery_sequence(
 		/* 3. wait receiver to lock-on*/
 		wait_time_microsec = lt_settings->cr_pattern_time;
 
-		if (!link->is_lttpr_mode_transparent)
+		if (link->lttpr_non_transparent_mode)
 			wait_time_microsec = TRAINING_AUX_RD_INTERVAL;
 
 		wait_for_training_aux_rd_interval(
@@ -1268,7 +1268,7 @@ static void configure_lttpr_mode(struct dc_link *link)
 		link->dpcd_caps.lttpr_caps.mode = repeater_mode;
 	}
 
-	if (!link->is_lttpr_mode_transparent) {
+	if (link->lttpr_non_transparent_mode) {
 
 		DC_LOG_HW_LINK_TRAINING("%s\n Set LTTPR to Non Transparent Mode\n", __func__);
 
@@ -1473,7 +1473,7 @@ enum link_training_result dc_link_dp_perform_link_training(
 			&lt_settings);
 
 	/* Configure lttpr mode */
-	if (!link->is_lttpr_mode_transparent)
+	if (link->lttpr_non_transparent_mode)
 		configure_lttpr_mode(link);
 
 	if (link->ctx->dc->work_arounds.lt_early_cr_pattern)
@@ -1489,7 +1489,7 @@ enum link_training_result dc_link_dp_perform_link_training(
 
 	dp_set_fec_ready(link, fec_enable);
 
-	if (!link->is_lttpr_mode_transparent) {
+	if (link->lttpr_non_transparent_mode) {
 
 		/* 2. perform link training (set link training done
 		 *  to false is done as well)
@@ -1756,7 +1756,7 @@ static struct dc_link_settings get_max_link_cap(struct dc_link *link)
 	 * account for lttpr repeaters cap
 	 * notes: repeaters do not snoop in the DPRX Capabilities addresses (3.6.3).
 	 */
-	if (!link->is_lttpr_mode_transparent) {
+	if (link->lttpr_non_transparent_mode) {
 		if (link->dpcd_caps.lttpr_caps.max_lane_count < max_link_cap.lane_count)
 			max_link_cap.lane_count = link->dpcd_caps.lttpr_caps.max_lane_count;
 
@@ -1914,7 +1914,7 @@ bool dp_verify_link_cap(
 	max_link_cap = get_max_link_cap(link);
 
 	/* Grant extended timeout request */
-	if (!link->is_lttpr_mode_transparent && link->dpcd_caps.lttpr_caps.max_ext_timeout > 0) {
+	if (link->lttpr_non_transparent_mode && link->dpcd_caps.lttpr_caps.max_ext_timeout > 0) {
 		uint8_t grant = link->dpcd_caps.lttpr_caps.max_ext_timeout & 0x80;
 
 		core_link_write_dpcd(link, DP_PHY_REPEATER_EXTENDED_WAIT_TIMEOUT, &grant, sizeof(grant));
@@ -3255,17 +3255,7 @@ static bool retrieve_link_cap(struct dc_link *link)
 	uint32_t read_dpcd_retry_cnt = 3;
 	int i;
 	struct dp_sink_hw_fw_revision dp_hw_fw_revision;
-
-	/* Set default timeout to 3.2ms and read LTTPR capabilities */
-	bool ext_timeout_support = link->dc->caps.extended_aux_timeout_support &&
-			!link->dc->config.disable_extended_timeout_support;
-
-	link->is_lttpr_mode_transparent = true;
-
-	if (ext_timeout_support) {
-		dc_link_aux_configure_timeout(link->ddc,
-					LINK_AUX_DEFAULT_EXTENDED_TIMEOUT_PERIOD);
-	}
+	bool is_lttpr_present = false;
 
 	memset(dpcd_data, '\0', sizeof(dpcd_data));
 	memset(lttpr_dpcd_data, '\0', sizeof(lttpr_dpcd_data));
@@ -3274,6 +3264,13 @@ static bool retrieve_link_cap(struct dc_link *link)
 	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);
+
 	status = core_link_read_dpcd(link, DP_SET_POWER,
 				&dpcd_power_state, sizeof(dpcd_power_state));
 
@@ -3300,8 +3297,9 @@ static bool retrieve_link_cap(struct dc_link *link)
 		return false;
 	}
 
-	if (ext_timeout_support) {
-
+	if (link->dc->caps.extended_aux_timeout_support) {
+		/* By reading LTTPR capability, RX assumes that we will enable LTTPR extended aux timeout if LTTPR is present.
+		 * Therefore, only query LTTPR capability when LTTPR extended aux timeout is supported by hardware */
 		status = core_link_read_dpcd(
 				link,
 				DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV,
@@ -3332,20 +3330,21 @@ static bool retrieve_link_cap(struct dc_link *link)
 				lttpr_dpcd_data[DP_PHY_REPEATER_EXTENDED_WAIT_TIMEOUT -
 								DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV];
 
-		if (link->dpcd_caps.lttpr_caps.phy_repeater_cnt > 0 &&
+		is_lttpr_present = (link->dpcd_caps.lttpr_caps.phy_repeater_cnt > 0 &&
 				link->dpcd_caps.lttpr_caps.max_lane_count > 0 &&
 				link->dpcd_caps.lttpr_caps.max_lane_count <= 4 &&
-				link->dpcd_caps.lttpr_caps.revision.raw >= 0x14) {
-			link->is_lttpr_mode_transparent = false;
-		} else {
-			/*No lttpr reset timeout to its default value*/
-			link->is_lttpr_mode_transparent = true;
-			dc_link_aux_configure_timeout(link->ddc, LINK_AUX_DEFAULT_TIMEOUT_PERIOD);
-		}
-
+				link->dpcd_caps.lttpr_caps.revision.raw >= 0x14);
+		if (is_lttpr_present)
 			CONN_DATA_DETECT(link, lttpr_dpcd_data, sizeof(lttpr_dpcd_data), "LTTPR Caps: ");
 	}
 
+	/* decide lttpr non transparent mode */
+	link->lttpr_non_transparent_mode = is_lttpr_present && link->dc->config.allow_lttpr_non_transparent_mode;
+
+	if (!is_lttpr_present)
+		dc_link_aux_try_to_configure_timeout(link->ddc, LINK_AUX_DEFAULT_TIMEOUT_PERIOD);
+
+
 	{
 		union training_aux_rd_interval aux_rd_interval;
 

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

@@ -281,7 +281,7 @@ void dp_set_hw_lane_settings(
 {
 	struct link_encoder *encoder = link->link_enc;
 
-	if (!link->is_lttpr_mode_transparent && !is_immediate_downstream(link, offset))
+	if (link->lttpr_non_transparent_mode && !is_immediate_downstream(link, offset))
 		return;
 
 	/* call Encoder to set lane settings */

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

@@ -274,7 +274,7 @@ struct dc_config {
 	bool edp_not_connected;
 	bool force_enum_edp;
 	bool forced_clocks;
-	bool disable_extended_timeout_support; // Used to disable extended timeout and lttpr feature as well
+	bool allow_lttpr_non_transparent_mode;
 	bool multi_mon_pp_mclk_switch;
 	bool disable_dmcu;
 	bool enable_4to1MPC;

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

@@ -101,6 +101,7 @@ struct dc_link {
 	bool aux_access_disabled;
 	bool sync_lt_in_progress;
 	bool is_lttpr_mode_transparent;
+	bool lttpr_non_transparent_mode;
 
 	/* caps is the same as reported_link_cap. link_traing use
 	 * reported_link_cap. Will clean up.  TODO

drivers/gpu/drm/amd/display/dc/inc/dc_link_ddc.h

@@ -105,7 +105,7 @@ int dc_link_aux_transfer_raw(struct ddc_service *ddc,
 bool dc_link_aux_transfer_with_retries(struct ddc_service *ddc,
 		struct aux_payload *payload);
 
-uint32_t dc_link_aux_configure_timeout(struct ddc_service *ddc,
+bool dc_link_aux_try_to_configure_timeout(struct ddc_service *ddc,
 		uint32_t timeout);
 
 void dal_ddc_service_write_scdc_data(

drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h

@@ -28,7 +28,7 @@
 
 #define LINK_TRAINING_ATTEMPTS 4
 #define LINK_TRAINING_RETRY_DELAY 50 /* ms */
-#define LINK_AUX_DEFAULT_EXTENDED_TIMEOUT_PERIOD 3200 /*us*/
+#define LINK_AUX_DEFAULT_LTTPR_TIMEOUT_PERIOD 3200 /*us*/
 #define LINK_AUX_DEFAULT_TIMEOUT_PERIOD 552 /*us*/
 
 struct dc_link;