drm/i915: Switch to LTTPR non-transparent mode link training

The DP Standard's recommendation is to use the LTTPR non-transparent
mode link training if LTTPRs are detected, so let's do this.

Besides power-saving, the advantages of this are that the maximum number
of LTTPRs can only be used in non-transparent mode (the limit is 5-8 in
transparent mode), and it provides a way to narrow down the reason for a
link training failure to a given link segment. Non-transparent mode is
probably also the mode that was tested the most by the industry.

The changes in this patchset:
- Pass the DP PHY that is currently link trained to all LT helpers, so
  that these can access the correct LTTPR/DPRX DPCD registers.
- During LT take into account the LTTPR common lane rate/count and the
  per LTTPR-PHY vswing/pre-emph limits.
- Switch to LTTPR non-transparent LT mode and train each link segment
  according to the sequence in DP Standard v2.0 (complete CR/EQ for
  each segment before continuing with the next segment).

v2:
- Switch to non-transparent mode during connector detection, which is
  required before reading the per-PHY LTTPR capabilities.
- Move the DP_PHY_LTTPR() macro to drm_dp_helper.h (Ville)
- Use the new drm_dp_dpcd_read_phy_link_status() instead of adding the
  same logic to intel_dp_get_link_status(). (Ville)
- Make intel_dp_lttpr_phy_caps() return a pointer to the whole array
  instead of a pointer to its first element. (Ville)
- Add the intel_dp_phy_is_downstream_of_source() helper. (Ville)
- Add a code comment about the disable->enable quirk of
  non-transparent mode.
- Add the intel_dp_training_pattern_set_reg() helper.
- Fix checkpatch/sparse warns.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201007170917.1764556-7-imre.deak@intel.com

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -1303,6 +1303,7 @@ struct intel_dp {
 	u8 edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE];
 	u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE];
 	u8 lttpr_common_caps[DP_LTTPR_COMMON_CAP_SIZE];
+	u8 lttpr_phy_caps[DP_MAX_LTTPR_COUNT][DP_LTTPR_PHY_CAP_SIZE];
 	u8 fec_capable;
 	/* source rates */
 	int num_source_rates;

drivers/gpu/drm/i915/display/intel_dp.c

@@ -160,6 +160,7 @@ static void intel_dp_set_sink_rates(struct intel_dp *intel_dp)
 		162000, 270000, 540000, 810000
 	};
 	int i, max_rate;
+	int max_lttpr_rate;
 
 	if (drm_dp_has_quirk(&intel_dp->desc, 0,
 			     DP_DPCD_QUIRK_CAN_DO_MAX_LINK_RATE_3_24_GBPS)) {
@@ -173,6 +174,9 @@ static void intel_dp_set_sink_rates(struct intel_dp *intel_dp)
 	}
 
 	max_rate = drm_dp_bw_code_to_link_rate(intel_dp->dpcd[DP_MAX_LINK_RATE]);
+	max_lttpr_rate = drm_dp_lttpr_max_link_rate(intel_dp->lttpr_common_caps);
+	if (max_lttpr_rate)
+		max_rate = min(max_rate, max_lttpr_rate);
 
 	for (i = 0; i < ARRAY_SIZE(dp_rates); i++) {
 		if (dp_rates[i] > max_rate)
@@ -218,6 +222,10 @@ static int intel_dp_max_common_lane_count(struct intel_dp *intel_dp)
 	int source_max = dig_port->max_lanes;
 	int sink_max = drm_dp_max_lane_count(intel_dp->dpcd);
 	int fia_max = intel_tc_port_fia_max_lane_count(dig_port);
+	int lttpr_max = drm_dp_lttpr_max_lane_count(intel_dp->lttpr_common_caps);
+
+	if (lttpr_max)
+		sink_max = min(sink_max, lttpr_max);
 
 	return min3(source_max, sink_max, fia_max);
 }
@@ -4179,17 +4187,6 @@ static void chv_dp_post_pll_disable(struct intel_atomic_state *state,
 	chv_phy_post_pll_disable(encoder, old_crtc_state);
 }
 
-/*
- * Fetch AUX CH registers 0x202 - 0x207 which contain
- * link status information
- */
-bool
-intel_dp_get_link_status(struct intel_dp *intel_dp, u8 link_status[DP_LINK_STATUS_SIZE])
-{
-	return drm_dp_dpcd_read(&intel_dp->aux, DP_LANE0_1_STATUS, link_status,
-				DP_LINK_STATUS_SIZE) == DP_LINK_STATUS_SIZE;
-}
-
 static u8 intel_dp_voltage_max_2(struct intel_dp *intel_dp,
 				 const struct intel_crtc_state *crtc_state)
 {
@@ -5592,13 +5589,15 @@ static void intel_dp_process_phy_request(struct intel_dp *intel_dp,
 		&intel_dp->compliance.test_data.phytest;
 	u8 link_status[DP_LINK_STATUS_SIZE];
 
-	if (!intel_dp_get_link_status(intel_dp, link_status)) {
+	if (drm_dp_dpcd_read_phy_link_status(&intel_dp->aux, DP_PHY_DPRX,
+					     link_status) < 0) {
 		DRM_DEBUG_KMS("failed to get link status\n");
 		return;
 	}
 
 	/* retrieve vswing & pre-emphasis setting */
-	intel_dp_get_adjust_train(intel_dp, crtc_state, link_status);
+	intel_dp_get_adjust_train(intel_dp, crtc_state, DP_PHY_DPRX,
+				  link_status);
 
 	intel_dp_autotest_phy_ddi_disable(intel_dp, crtc_state);
 
@@ -5756,7 +5755,8 @@ intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
 	if (intel_psr_enabled(intel_dp))
 		return false;
 
-	if (!intel_dp_get_link_status(intel_dp, link_status))
+	if (drm_dp_dpcd_read_phy_link_status(&intel_dp->aux, DP_PHY_DPRX,
+					     link_status) < 0)
 		return false;
 
 	/*

drivers/gpu/drm/i915/display/intel_dp.h

@@ -102,8 +102,6 @@ void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
 			   u8 *link_bw, u8 *rate_select);
 bool intel_dp_source_supports_hbr2(struct intel_dp *intel_dp);
 bool intel_dp_source_supports_hbr3(struct intel_dp *intel_dp);
-bool
-intel_dp_get_link_status(struct intel_dp *intel_dp, u8 *link_status);
 
 bool intel_dp_get_colorimetry_status(struct intel_dp *intel_dp);
 int intel_dp_link_required(int pixel_clock, int bpp);

drivers/gpu/drm/i915/display/intel_dp_link_training.c

@@ -34,6 +34,63 @@ intel_dp_dump_link_status(const u8 link_status[DP_LINK_STATUS_SIZE])
 		      link_status[3], link_status[4], link_status[5]);
 }
 
+static int intel_dp_lttpr_count(struct intel_dp *intel_dp)
+{
+	int count = drm_dp_lttpr_count(intel_dp->lttpr_common_caps);
+
+	/*
+	 * Pretend no LTTPRs in case of LTTPR detection error, or
+	 * if too many (>8) LTTPRs are detected. This translates to link
+	 * training in transparent mode.
+	 */
+	return count <= 0 ? 0 : count;
+}
+
+static void intel_dp_reset_lttpr_count(struct intel_dp *intel_dp)
+{
+	intel_dp->lttpr_common_caps[DP_PHY_REPEATER_CNT -
+				    DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV] = 0;
+}
+
+static const char *intel_dp_phy_name(enum drm_dp_phy dp_phy,
+				     char *buf, size_t buf_size)
+{
+	if (dp_phy == DP_PHY_DPRX)
+		snprintf(buf, buf_size, "DPRX");
+	else
+		snprintf(buf, buf_size, "LTTPR %d", dp_phy - DP_PHY_LTTPR1 + 1);
+
+	return buf;
+}
+
+static u8 *intel_dp_lttpr_phy_caps(struct intel_dp *intel_dp,
+				   enum drm_dp_phy dp_phy)
+{
+	return intel_dp->lttpr_phy_caps[dp_phy - DP_PHY_LTTPR1];
+}
+
+static void intel_dp_read_lttpr_phy_caps(struct intel_dp *intel_dp,
+					 enum drm_dp_phy dp_phy)
+{
+	u8 *phy_caps = intel_dp_lttpr_phy_caps(intel_dp, dp_phy);
+	char phy_name[10];
+
+	intel_dp_phy_name(dp_phy, phy_name, sizeof(phy_name));
+
+	if (drm_dp_read_lttpr_phy_caps(&intel_dp->aux, dp_phy, phy_caps) < 0) {
+		drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
+			    "failed to read the PHY caps for %s\n",
+			    phy_name);
+		return;
+	}
+
+	drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
+		    "%s PHY capabilities: %*ph\n",
+		    phy_name,
+		    (int)sizeof(intel_dp->lttpr_phy_caps[0]),
+		    phy_caps);
+}
+
 static bool intel_dp_read_lttpr_common_caps(struct intel_dp *intel_dp)
 {
 	if (drm_dp_read_lttpr_common_caps(&intel_dp->aux,
@@ -64,24 +121,64 @@ intel_dp_set_lttpr_transparent_mode(struct intel_dp *intel_dp, bool enable)
  * intel_dp_lttpr_init - detect LTTPRs and init the LTTPR link training mode
  * @intel_dp: Intel DP struct
  *
- * Read the LTTPR common capabilities and switch to transparent link training
- * mode.
+ * Read the LTTPR common capabilities, switch to non-transparent link training
+ * mode if any is detected and read the PHY capabilities for all detected
+ * LTTPRs. In case of an LTTPR detection error or if the number of
+ * LTTPRs is more than is supported (8), fall back to the no-LTTPR,
+ * transparent mode link training mode.
+ *
+ * Returns:
+ *   >0  if LTTPRs were detected and the non-transparent LT mode was set
+ *    0  if no LTTPRs or more than 8 LTTPRs were detected or in case of a
+ *       detection failure and the transparent LT mode was set
  */
 int intel_dp_lttpr_init(struct intel_dp *intel_dp)
 {
+	int lttpr_count;
+	bool ret;
+	int i;
+
 	if (intel_dp_is_edp(intel_dp))
 		return 0;
 
-	intel_dp_read_lttpr_common_caps(intel_dp);
+	ret = intel_dp_read_lttpr_common_caps(intel_dp);
 
 	/*
 	 * See DP Standard v2.0 3.6.6.1. about the explicit disabling of
-	 * non-transparent mode.
+	 * non-transparent mode and the disable->enable non-transparent mode
+	 * sequence.
 	 */
 	intel_dp_set_lttpr_transparent_mode(intel_dp, true);
 
-	return 0;
+	if (!ret)
+		return 0;
+
+	lttpr_count = intel_dp_lttpr_count(intel_dp);
+
+	/*
+	 * In case of unsupported number of LTTPRs or failing to switch to
+	 * non-transparent mode fall-back to transparent link training mode,
+	 * still taking into account any LTTPR common lane- rate/count limits.
+	 */
+	if (lttpr_count == 0)
+		return 0;
+
+	if (!intel_dp_set_lttpr_transparent_mode(intel_dp, false)) {
+		drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
+			    "Switching to LTTPR non-transparent LT mode failed, fall-back to transparent mode\n");
+
+		intel_dp_set_lttpr_transparent_mode(intel_dp, true);
+		intel_dp_reset_lttpr_count(intel_dp);
+
+		return 0;
+	}
+
+	for (i = 0; i < lttpr_count; i++)
+		intel_dp_read_lttpr_phy_caps(intel_dp, DP_PHY_LTTPR(i));
+
+	return lttpr_count;
 }
+EXPORT_SYMBOL(intel_dp_lttpr_init);
 
 static u8 dp_voltage_max(u8 preemph)
 {
@@ -98,12 +195,91 @@ static u8 dp_voltage_max(u8 preemph)
 	}
 }
 
+static u8 intel_dp_lttpr_voltage_max(struct intel_dp *intel_dp,
+				     enum drm_dp_phy dp_phy)
+{
+	const u8 *phy_caps = intel_dp_lttpr_phy_caps(intel_dp, dp_phy);
+
+	if (drm_dp_lttpr_voltage_swing_level_3_supported(phy_caps))
+		return DP_TRAIN_VOLTAGE_SWING_LEVEL_3;
+	else
+		return DP_TRAIN_VOLTAGE_SWING_LEVEL_2;
+}
+
+static u8 intel_dp_lttpr_preemph_max(struct intel_dp *intel_dp,
+				     enum drm_dp_phy dp_phy)
+{
+	const u8 *phy_caps = intel_dp_lttpr_phy_caps(intel_dp, dp_phy);
+
+	if (drm_dp_lttpr_pre_emphasis_level_3_supported(phy_caps))
+		return DP_TRAIN_PRE_EMPH_LEVEL_3;
+	else
+		return DP_TRAIN_PRE_EMPH_LEVEL_2;
+}
+
+static bool
+intel_dp_phy_is_downstream_of_source(struct intel_dp *intel_dp,
+				     enum drm_dp_phy dp_phy)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	int lttpr_count = intel_dp_lttpr_count(intel_dp);
+
+	drm_WARN_ON_ONCE(&i915->drm, lttpr_count == 0 && dp_phy != DP_PHY_DPRX);
+
+	return lttpr_count == 0 || dp_phy == DP_PHY_LTTPR(lttpr_count - 1);
+}
+
+static u8 intel_dp_phy_voltage_max(struct intel_dp *intel_dp,
+				   const struct intel_crtc_state *crtc_state,
+				   enum drm_dp_phy dp_phy)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	u8 voltage_max;
+
+	/*
+	 * Get voltage_max from the DPTX_PHY (source or LTTPR) upstream from
+	 * the DPRX_PHY we train.
+	 */
+	if (intel_dp_phy_is_downstream_of_source(intel_dp, dp_phy))
+		voltage_max = intel_dp->voltage_max(intel_dp, crtc_state);
+	else
+		voltage_max = intel_dp_lttpr_voltage_max(intel_dp, dp_phy + 1);
+
+	drm_WARN_ON_ONCE(&i915->drm,
+			 voltage_max != DP_TRAIN_VOLTAGE_SWING_LEVEL_2 &&
+			 voltage_max != DP_TRAIN_VOLTAGE_SWING_LEVEL_3);
+
+	return voltage_max;
+}
+
+static u8 intel_dp_phy_preemph_max(struct intel_dp *intel_dp,
+				   enum drm_dp_phy dp_phy)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	u8 preemph_max;
+
+	/*
+	 * Get preemph_max from the DPTX_PHY (source or LTTPR) upstream from
+	 * the DPRX_PHY we train.
+	 */
+	if (intel_dp_phy_is_downstream_of_source(intel_dp, dp_phy))
+		preemph_max = intel_dp->preemph_max(intel_dp);
+	else
+		preemph_max = intel_dp_lttpr_preemph_max(intel_dp, dp_phy + 1);
+
+	drm_WARN_ON_ONCE(&i915->drm,
+			 preemph_max != DP_TRAIN_PRE_EMPH_LEVEL_2 &&
+			 preemph_max != DP_TRAIN_PRE_EMPH_LEVEL_3);
+
+	return preemph_max;
+}
+
 void
 intel_dp_get_adjust_train(struct intel_dp *intel_dp,
 			  const struct intel_crtc_state *crtc_state,
+			  enum drm_dp_phy dp_phy,
 			  const u8 link_status[DP_LINK_STATUS_SIZE])
 {
-	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 	u8 v = 0;
 	u8 p = 0;
 	int lane;
@@ -115,21 +291,13 @@ intel_dp_get_adjust_train(struct intel_dp *intel_dp,
 		p = max(p, drm_dp_get_adjust_request_pre_emphasis(link_status, lane));
 	}
 
-	preemph_max = intel_dp->preemph_max(intel_dp);
-	drm_WARN_ON_ONCE(&i915->drm,
-			 preemph_max != DP_TRAIN_PRE_EMPH_LEVEL_2 &&
-			 preemph_max != DP_TRAIN_PRE_EMPH_LEVEL_3);
-
+	preemph_max = intel_dp_phy_preemph_max(intel_dp, dp_phy);
 	if (p >= preemph_max)
 		p = preemph_max | DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
 
 	v = min(v, dp_voltage_max(p));
 
-	voltage_max = intel_dp->voltage_max(intel_dp, crtc_state);
-	drm_WARN_ON_ONCE(&i915->drm,
-			 voltage_max != DP_TRAIN_VOLTAGE_SWING_LEVEL_2 &&
-			 voltage_max != DP_TRAIN_VOLTAGE_SWING_LEVEL_3);
-
+	voltage_max = intel_dp_phy_voltage_max(intel_dp, crtc_state, dp_phy);
 	if (v >= voltage_max)
 		v = voltage_max | DP_TRAIN_MAX_SWING_REACHED;
 
@@ -137,11 +305,21 @@ intel_dp_get_adjust_train(struct intel_dp *intel_dp,
 		intel_dp->train_set[lane] = v | p;
 }
 
+static int intel_dp_training_pattern_set_reg(struct intel_dp *intel_dp,
+					     enum drm_dp_phy dp_phy)
+{
+	return dp_phy == DP_PHY_DPRX ?
+		DP_TRAINING_PATTERN_SET :
+		DP_TRAINING_PATTERN_SET_PHY_REPEATER(dp_phy);
+}
+
 static bool
 intel_dp_set_link_train(struct intel_dp *intel_dp,
 			const struct intel_crtc_state *crtc_state,
+			enum drm_dp_phy dp_phy,
 			u8 dp_train_pat)
 {
+	int reg = intel_dp_training_pattern_set_reg(intel_dp, dp_phy);
 	u8 buf[sizeof(intel_dp->train_set) + 1];
 	int len;
 
@@ -153,29 +331,33 @@ intel_dp_set_link_train(struct intel_dp *intel_dp,
 	memcpy(buf + 1, intel_dp->train_set, crtc_state->lane_count);
 	len = crtc_state->lane_count + 1;
 
-	return drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_PATTERN_SET,
-				 buf, len) == len;
+	return drm_dp_dpcd_write(&intel_dp->aux, reg, buf, len) == len;
 }
 
 static bool
 intel_dp_reset_link_train(struct intel_dp *intel_dp,
 			  const struct intel_crtc_state *crtc_state,
+			  enum drm_dp_phy dp_phy,
 			  u8 dp_train_pat)
 {
 	memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
 	intel_dp_set_signal_levels(intel_dp, crtc_state);
-	return intel_dp_set_link_train(intel_dp, crtc_state, dp_train_pat);
+	return intel_dp_set_link_train(intel_dp, crtc_state, dp_phy, dp_train_pat);
 }
 
 static bool
 intel_dp_update_link_train(struct intel_dp *intel_dp,
-			   const struct intel_crtc_state *crtc_state)
+			   const struct intel_crtc_state *crtc_state,
+			   enum drm_dp_phy dp_phy)
 {
+	int reg = dp_phy == DP_PHY_DPRX ?
+			    DP_TRAINING_LANE0_SET :
+			    DP_TRAINING_LANE0_SET_PHY_REPEATER(dp_phy);
 	int ret;
 
 	intel_dp_set_signal_levels(intel_dp, crtc_state);
 
-	ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_LANE0_SET,
+	ret = drm_dp_dpcd_write(&intel_dp->aux, reg,
 				intel_dp->train_set, crtc_state->lane_count);
 
 	return ret == crtc_state->lane_count;
@@ -240,10 +422,23 @@ intel_dp_prepare_link_train(struct intel_dp *intel_dp,
 	return true;
 }
 
-/* Perform the link training clock recovery phase using training pattern 1. */
+static void intel_dp_link_training_clock_recovery_delay(struct intel_dp *intel_dp,
+							enum drm_dp_phy dp_phy)
+{
+	if (dp_phy == DP_PHY_DPRX)
+		drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
+	else
+		drm_dp_lttpr_link_train_clock_recovery_delay();
+}
+
+/*
+ * Perform the link training clock recovery phase on the given DP PHY using
+ * training pattern 1.
+ */
 static bool
 intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp,
-				      const struct intel_crtc_state *crtc_state)
+				      const struct intel_crtc_state *crtc_state,
+				      enum drm_dp_phy dp_phy)
 {
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 	u8 voltage;
@@ -251,7 +446,7 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp,
 	bool max_vswing_reached = false;
 
 	/* clock recovery */
-	if (!intel_dp_reset_link_train(intel_dp, crtc_state,
+	if (!intel_dp_reset_link_train(intel_dp, crtc_state, dp_phy,
 				       DP_TRAINING_PATTERN_1 |
 				       DP_LINK_SCRAMBLING_DISABLE)) {
 		drm_err(&i915->drm, "failed to enable link training\n");
@@ -275,9 +470,10 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp,
 	for (cr_tries = 0; cr_tries < max_cr_tries; ++cr_tries) {
 		u8 link_status[DP_LINK_STATUS_SIZE];
 
-		drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
+		intel_dp_link_training_clock_recovery_delay(intel_dp, dp_phy);
 
-		if (!intel_dp_get_link_status(intel_dp, link_status)) {
+		if (drm_dp_dpcd_read_phy_link_status(&intel_dp->aux, dp_phy,
+						     link_status) < 0) {
 			drm_err(&i915->drm, "failed to get link status\n");
 			return false;
 		}
@@ -301,8 +497,9 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp,
 		voltage = intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK;
 
 		/* Update training set as requested by target */
-		intel_dp_get_adjust_train(intel_dp, crtc_state, link_status);
-		if (!intel_dp_update_link_train(intel_dp, crtc_state)) {
+		intel_dp_get_adjust_train(intel_dp, crtc_state, dp_phy,
+					  link_status);
+		if (!intel_dp_update_link_train(intel_dp, crtc_state, dp_phy)) {
 			drm_err(&i915->drm,
 				"failed to update link training\n");
 			return false;
@@ -329,7 +526,8 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp,
  * or 1.2 devices that support it, Training Pattern 2 otherwise.
  */
 static u32 intel_dp_training_pattern(struct intel_dp *intel_dp,
-				     const struct intel_crtc_state *crtc_state)
+				     const struct intel_crtc_state *crtc_state,
+				     enum drm_dp_phy dp_phy)
 {
 	bool source_tps3, sink_tps3, source_tps4, sink_tps4;
 
@@ -338,9 +536,11 @@ static u32 intel_dp_training_pattern(struct intel_dp *intel_dp,
 	 * for all downstream devices that support HBR3. There are no known eDP
 	 * panels that support TPS4 as of Feb 2018 as per VESA eDP_v1.4b_E1
 	 * specification.
+	 * LTTPRs must support TPS4.
 	 */
 	source_tps4 = intel_dp_source_supports_hbr3(intel_dp);
-	sink_tps4 = drm_dp_tps4_supported(intel_dp->dpcd);
+	sink_tps4 = dp_phy != DP_PHY_DPRX ||
+		    drm_dp_tps4_supported(intel_dp->dpcd);
 	if (source_tps4 && sink_tps4) {
 		return DP_TRAINING_PATTERN_4;
 	} else if (crtc_state->port_clock == 810000) {
@@ -357,7 +557,8 @@ static u32 intel_dp_training_pattern(struct intel_dp *intel_dp,
 	 * all sinks follow the spec.
 	 */
 	source_tps3 = intel_dp_source_supports_hbr2(intel_dp);
-	sink_tps3 = drm_dp_tps3_supported(intel_dp->dpcd);
+	sink_tps3 = dp_phy != DP_PHY_DPRX ||
+		    drm_dp_tps3_supported(intel_dp->dpcd);
 	if (source_tps3 && sink_tps3) {
 		return  DP_TRAINING_PATTERN_3;
 	} else if (crtc_state->port_clock >= 540000) {
@@ -372,13 +573,28 @@ static u32 intel_dp_training_pattern(struct intel_dp *intel_dp,
 	return DP_TRAINING_PATTERN_2;
 }
 
+static void
+intel_dp_link_training_channel_equalization_delay(struct intel_dp *intel_dp,
+						  enum drm_dp_phy dp_phy)
+{
+	if (dp_phy == DP_PHY_DPRX) {
+		drm_dp_link_train_channel_eq_delay(intel_dp->dpcd);
+	} else {
+		const u8 *phy_caps = intel_dp_lttpr_phy_caps(intel_dp, dp_phy);
+
+		drm_dp_lttpr_link_train_channel_eq_delay(phy_caps);
+	}
+}
+
 /*
- * Perform the link training channel equalization phase using one of training
- * pattern 2, 3 or 4 depending on the source and sink capabilities.
+ * Perform the link training channel equalization phase on the given DP PHY
+ * using one of training pattern 2, 3 or 4 depending on the source and
+ * sink capabilities.
  */
 static bool
 intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp,
-					    const struct intel_crtc_state *crtc_state)
+					    const struct intel_crtc_state *crtc_state,
+					    enum drm_dp_phy dp_phy)
 {
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 	int tries;
@@ -386,22 +602,23 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp,
 	u8 link_status[DP_LINK_STATUS_SIZE];
 	bool channel_eq = false;
 
-	training_pattern = intel_dp_training_pattern(intel_dp, crtc_state);
+	training_pattern = intel_dp_training_pattern(intel_dp, crtc_state, dp_phy);
 	/* Scrambling is disabled for TPS2/3 and enabled for TPS4 */
 	if (training_pattern != DP_TRAINING_PATTERN_4)
 		training_pattern |= DP_LINK_SCRAMBLING_DISABLE;
 
 	/* channel equalization */
-	if (!intel_dp_set_link_train(intel_dp, crtc_state,
+	if (!intel_dp_set_link_train(intel_dp, crtc_state, dp_phy,
 				     training_pattern)) {
 		drm_err(&i915->drm, "failed to start channel equalization\n");
 		return false;
 	}
 
 	for (tries = 0; tries < 5; tries++) {
-
-		drm_dp_link_train_channel_eq_delay(intel_dp->dpcd);
-		if (!intel_dp_get_link_status(intel_dp, link_status)) {
+		intel_dp_link_training_channel_equalization_delay(intel_dp,
+								  dp_phy);
+		if (drm_dp_dpcd_read_phy_link_status(&intel_dp->aux, dp_phy,
+						     link_status) < 0) {
 			drm_err(&i915->drm,
 				"failed to get link status\n");
 			break;
@@ -426,8 +643,9 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp,
 		}
 
 		/* Update training set as requested by target */
-		intel_dp_get_adjust_train(intel_dp, crtc_state, link_status);
-		if (!intel_dp_update_link_train(intel_dp, crtc_state)) {
+		intel_dp_get_adjust_train(intel_dp, crtc_state, dp_phy,
+					  link_status);
+		if (!intel_dp_update_link_train(intel_dp, crtc_state, dp_phy)) {
 			drm_err(&i915->drm,
 				"failed to update link training\n");
 			break;
@@ -441,17 +659,16 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp,
 			    "Channel equalization failed 5 times\n");
 	}
 
-	if (intel_dp->set_idle_link_train)
-		intel_dp->set_idle_link_train(intel_dp, crtc_state);
-
 	return channel_eq;
 }
 
-static bool intel_dp_disable_dpcd_training_pattern(struct intel_dp *intel_dp)
+static bool intel_dp_disable_dpcd_training_pattern(struct intel_dp *intel_dp,
+						   enum drm_dp_phy dp_phy)
 {
+	int reg = intel_dp_training_pattern_set_reg(intel_dp, dp_phy);
 	u8 val = DP_TRAINING_PATTERN_DISABLE;
 
-	return drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_PATTERN_SET, &val, 1) == 1;
+	return drm_dp_dpcd_write(&intel_dp->aux, reg, &val, 1) == 1;
 }
 
 /**
@@ -478,33 +695,34 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp,
 	intel_dp_program_link_training_pattern(intel_dp,
 					       crtc_state,
 					       DP_TRAINING_PATTERN_DISABLE);
-	intel_dp_disable_dpcd_training_pattern(intel_dp);
+	intel_dp_disable_dpcd_training_pattern(intel_dp, DP_PHY_DPRX);
 }
 
 static bool
-intel_dp_link_train(struct intel_dp *intel_dp,
-		    const struct intel_crtc_state *crtc_state)
+intel_dp_link_train_phy(struct intel_dp *intel_dp,
+			const struct intel_crtc_state *crtc_state,
+			enum drm_dp_phy dp_phy)
 {
 	struct intel_connector *intel_connector = intel_dp->attached_connector;
+	char phy_name[10];
 	bool ret = false;
 
-	intel_dp_prepare_link_train(intel_dp, crtc_state);
-
-	if (!intel_dp_link_training_clock_recovery(intel_dp, crtc_state))
+	if (!intel_dp_link_training_clock_recovery(intel_dp, crtc_state, dp_phy))
 		goto out;
 
-	if (!intel_dp_link_training_channel_equalization(intel_dp, crtc_state))
+	if (!intel_dp_link_training_channel_equalization(intel_dp, crtc_state, dp_phy))
 		goto out;
 
 	ret = true;
 
 out:
 	drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
-		    "[CONNECTOR:%d:%s] Link Training %s at link rate = %d, lane count = %d",
+		    "[CONNECTOR:%d:%s] Link Training %s at link rate = %d, lane count = %d, at %s",
 		    intel_connector->base.base.id,
 		    intel_connector->base.name,
 		    ret ? "passed" : "failed",
-		    crtc_state->port_clock, crtc_state->lane_count);
+		    crtc_state->port_clock, crtc_state->lane_count,
+		    intel_dp_phy_name(dp_phy, phy_name, sizeof(phy_name)));
 
 	return ret;
 }
@@ -528,6 +746,36 @@ static void intel_dp_schedule_fallback_link_training(struct intel_dp *intel_dp,
 	schedule_work(&intel_connector->modeset_retry_work);
 }
 
+/* Perform the link training on all LTTPRs and the DPRX on a link. */
+static bool
+intel_dp_link_train_all_phys(struct intel_dp *intel_dp,
+			     const struct intel_crtc_state *crtc_state,
+			     int lttpr_count)
+{
+	bool ret = true;
+	int i;
+
+	intel_dp_prepare_link_train(intel_dp, crtc_state);
+
+	for (i = lttpr_count - 1; i >= 0; i--) {
+		enum drm_dp_phy dp_phy = DP_PHY_LTTPR(i);
+
+		ret = intel_dp_link_train_phy(intel_dp, crtc_state, dp_phy);
+		intel_dp_disable_dpcd_training_pattern(intel_dp, dp_phy);
+
+		if (!ret)
+			break;
+	}
+
+	if (ret)
+		intel_dp_link_train_phy(intel_dp, crtc_state, DP_PHY_DPRX);
+
+	if (intel_dp->set_idle_link_train)
+		intel_dp->set_idle_link_train(intel_dp, crtc_state);
+
+	return ret;
+}
+
 /**
  * intel_dp_start_link_train - start link training
  * @intel_dp: DP struct
@@ -545,8 +793,8 @@ void intel_dp_start_link_train(struct intel_dp *intel_dp,
 	 * TODO: Reiniting LTTPRs here won't be needed once proper connector
 	 * HW state readout is added.
 	 */
-	intel_dp_lttpr_init(intel_dp);
+	int lttpr_count = intel_dp_lttpr_init(intel_dp);
 
-	if (!intel_dp_link_train(intel_dp, crtc_state))
+	if (!intel_dp_link_train_all_phys(intel_dp, crtc_state, lttpr_count))
 		intel_dp_schedule_fallback_link_training(intel_dp, crtc_state);
 }

drivers/gpu/drm/i915/display/intel_dp_link_training.h

@@ -15,6 +15,7 @@ int intel_dp_lttpr_init(struct intel_dp *intel_dp);
 
 void intel_dp_get_adjust_train(struct intel_dp *intel_dp,
 			       const struct intel_crtc_state *crtc_state,
+			       enum drm_dp_phy dp_phy,
 			       const u8 link_status[DP_LINK_STATUS_SIZE]);
 void intel_dp_start_link_train(struct intel_dp *intel_dp,
 			       const struct intel_crtc_state *crtc_state);