[PATCH v3 11/43] drm/bridge: analogix_dp: add fast link train for eDP

[Thierry Escande]

From: zain wang <wzz@xxxxxxxxxxxxxx>

We would meet a short black screen when exit PSR with the full link
training, In this case, we should use fast link train instead of full
link training.

Signed-off-by: zain wang <wzz@xxxxxxxxxxxxxx>
Signed-off-by: Sean Paul <seanpaul@xxxxxxxxxxxx>
Signed-off-by: Thierry Escande <thierry.escande@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 142 ++++++++++++++++-----
 drivers/gpu/drm/bridge/analogix/analogix_dp_core.h |   3 +
 2 files changed, 114 insertions(+), 31 deletions(-)

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index 84141571e960..e0775adf80b3 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -10,17 +10,18 @@
 * option) any later version.
 */
 
-#include <linux/module.h>
-#include <linux/platform_device.h>
-#include <linux/err.h>
 #include <linux/clk.h>
-#include <linux/io.h>
+#include <linux/component.h>
+#include <linux/err.h>
+#include <linux/gpio.h>
 #include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_gpio.h>
-#include <linux/gpio.h>
-#include <linux/component.h>
 #include <linux/phy/phy.h>
+#include <linux/platform_device.h>
 
 #include <drm/drmP.h>
 #include <drm/drm_atomic_helper.h>
@@ -35,6 +36,8 @@
 
 #define to_dp(nm)	container_of(nm, struct analogix_dp_device, nm)
 
+static const bool verify_fast_training;
+
 struct bridge_init {
 	struct i2c_client *client;
 	struct device_node *node;
@@ -528,7 +531,7 @@ static int analogix_dp_process_equalizer_training(struct analogix_dp_device *dp)
 {
 	int lane, lane_count, retval;
 	u32 reg;
-	u8 link_align, link_status[2], adjust_request[2];
+	u8 link_align, link_status[2], adjust_request[2], spread;
 
 	usleep_range(400, 401);
 
@@ -571,6 +574,20 @@ static int analogix_dp_process_equalizer_training(struct analogix_dp_device *dp)
 		dev_dbg(dp->dev, "final lane count = %.2x\n",
 			dp->link_train.lane_count);
 
+		retval = drm_dp_dpcd_readb(&dp->aux, DP_MAX_DOWNSPREAD,
+					   &spread);
+		if (retval != 1) {
+			dev_err(dp->dev, "failed to read downspread %d\n",
+				retval);
+			dp->fast_train_support = false;
+		} else {
+			dp->fast_train_support =
+				(spread & DP_NO_AUX_HANDSHAKE_LINK_TRAINING) ?
+					true : false;
+		}
+		dev_dbg(dp->dev, "fast link training %s\n",
+			dp->fast_train_support ? "supported" : "unsupported");
+
 		/* set enhanced mode if available */
 		analogix_dp_set_enhanced_mode(dp);
 		dp->link_train.lt_state = FINISHED;
@@ -627,10 +644,12 @@ static void analogix_dp_get_max_rx_lane_count(struct analogix_dp_device *dp,
 	*lane_count = DPCD_MAX_LANE_COUNT(data);
 }
 
-static void analogix_dp_init_training(struct analogix_dp_device *dp,
-				      enum link_lane_count_type max_lane,
-				      int max_rate)
+static int analogix_dp_full_link_train(struct analogix_dp_device *dp,
+				       u32 max_lanes, u32 max_rate)
 {
+	int retval = 0;
+	bool training_finished = false;
+
 	/*
 	 * MACRO_RST must be applied after the PLL_LOCK to avoid
 	 * the DP inter pair skew issue for at least 10 us
@@ -656,18 +675,13 @@ static void analogix_dp_init_training(struct analogix_dp_device *dp,
 	}
 
 	/* Setup TX lane count & rate */
-	if (dp->link_train.lane_count > max_lane)
-		dp->link_train.lane_count = max_lane;
+	if (dp->link_train.lane_count > max_lanes)
+		dp->link_train.lane_count = max_lanes;
 	if (dp->link_train.link_rate > max_rate)
 		dp->link_train.link_rate = max_rate;
 
 	/* All DP analog module power up */
 	analogix_dp_set_analog_power_down(dp, POWER_ALL, 0);
-}
-
-static int analogix_dp_sw_link_training(struct analogix_dp_device *dp)
-{
-	int retval = 0, training_finished = 0;
 
 	dp->link_train.lt_state = START;
 
@@ -702,22 +716,88 @@ static int analogix_dp_sw_link_training(struct analogix_dp_device *dp)
 	return retval;
 }
 
-static int analogix_dp_set_link_train(struct analogix_dp_device *dp,
-				      u32 count, u32 bwtype)
+static int analogix_dp_fast_link_train(struct analogix_dp_device *dp)
 {
-	int i;
-	int retval;
+	int i, ret;
+	u8 link_align, link_status[2];
+	enum pll_status status;
 
-	for (i = 0; i < DP_TIMEOUT_LOOP_COUNT; i++) {
-		analogix_dp_init_training(dp, count, bwtype);
-		retval = analogix_dp_sw_link_training(dp);
-		if (retval == 0)
-			break;
+	analogix_dp_reset_macro(dp);
 
-		usleep_range(100, 110);
+	analogix_dp_set_link_bandwidth(dp, dp->link_train.link_rate);
+	analogix_dp_set_lane_count(dp, dp->link_train.lane_count);
+
+	for (i = 0; i < dp->link_train.lane_count; i++) {
+		analogix_dp_set_lane_link_training(dp,
+			dp->link_train.training_lane[i], i);
 	}
 
-	return retval;
+	ret = readx_poll_timeout(analogix_dp_get_pll_lock_status, dp, status,
+				 status != PLL_UNLOCKED, 120,
+				 120 * DP_TIMEOUT_LOOP_COUNT);
+	if (ret) {
+		DRM_DEV_ERROR(dp->dev, "Wait for pll lock failed %d\n", ret);
+		return ret;
+	}
+
+	/* source Set training pattern 1 */
+	analogix_dp_set_training_pattern(dp, TRAINING_PTN1);
+	/* From DP spec, pattern must be on-screen for a minimum 500us */
+	usleep_range(500, 600);
+
+	analogix_dp_set_training_pattern(dp, TRAINING_PTN2);
+	/* From DP spec, pattern must be on-screen for a minimum 500us */
+	usleep_range(500, 600);
+
+	/* TODO: enhanced_mode?*/
+	analogix_dp_set_training_pattern(dp, DP_NONE);
+
+	/*
+	 * Useful for debugging issues with fast link training, disable for more
+	 * speed
+	 */
+	if (verify_fast_training) {
+		ret = drm_dp_dpcd_readb(&dp->aux, DP_LANE_ALIGN_STATUS_UPDATED,
+					&link_align);
+		if (ret < 0) {
+			DRM_DEV_ERROR(dp->dev, "Read align status failed %d\n",
+				      ret);
+			return ret;
+		}
+
+		ret = drm_dp_dpcd_read(&dp->aux, DP_LANE0_1_STATUS, link_status,
+				       2);
+		if (ret < 0) {
+			DRM_DEV_ERROR(dp->dev, "Read link status failed %d\n",
+				      ret);
+			return ret;
+		}
+
+		if (analogix_dp_clock_recovery_ok(link_status,
+						  dp->link_train.lane_count)) {
+			DRM_DEV_ERROR(dp->dev, "Clock recovery failed\n");
+			analogix_dp_reduce_link_rate(dp);
+			return -EIO;
+		}
+
+		if (analogix_dp_channel_eq_ok(link_status, link_align,
+					      dp->link_train.lane_count)) {
+			DRM_DEV_ERROR(dp->dev, "Channel EQ failed\n");
+			analogix_dp_reduce_link_rate(dp);
+			return -EIO;
+		}
+	}
+
+	return 0;
+}
+
+static int analogix_dp_train_link(struct analogix_dp_device *dp)
+{
+	if (dp->fast_train_support)
+		return analogix_dp_fast_link_train(dp);
+
+	return analogix_dp_full_link_train(dp, dp->video_info.max_lane_count,
+					   dp->video_info.max_link_rate);
 }
 
 static int analogix_dp_config_video(struct analogix_dp_device *dp)
@@ -850,10 +930,10 @@ static void analogix_dp_commit(struct analogix_dp_device *dp)
 			DRM_ERROR("failed to disable the panel\n");
 	}
 
-	ret = analogix_dp_set_link_train(dp, dp->video_info.max_lane_count,
-					 dp->video_info.max_link_rate);
+	ret = readx_poll_timeout(analogix_dp_train_link, dp, ret, !ret, 100,
+				 DP_TIMEOUT_TRAINING_US * 5);
 	if (ret) {
-		dev_err(dp->dev, "unable to do link train\n");
+		dev_err(dp->dev, "unable to do link train, ret=%d\n", ret);
 		return;
 	}
 
diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
index e135a42cb19e..920607d7eb3e 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
@@ -20,6 +20,8 @@
 #define MAX_CR_LOOP 5
 #define MAX_EQ_LOOP 5
 
+/* Training takes 22ms if AUX channel comm fails. Use this as retry interval */
+#define DP_TIMEOUT_TRAINING_US			22000
 #define DP_TIMEOUT_PSR_LOOP_MS			300
 
 /* DP_MAX_LANE_COUNT */
@@ -171,6 +173,7 @@ struct analogix_dp_device {
 	int			hpd_gpio;
 	bool                    force_hpd;
 	bool			psr_enable;
+	bool			fast_train_support;
 
 	struct mutex		panel_lock;
 	bool			panel_is_modeset;
-- 
2.14.1