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>

1 files changed, 29 insertions, 30 deletions

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index 91cd884d6f25..4b3a3e8b6401 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/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);
-		}
-
-		CONN_DATA_DETECT(link, lttpr_dpcd_data, sizeof(lttpr_dpcd_data), "LTTPR Caps: ");
+				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;