video: exynos_dp: Check DPCD return codes

Add return code checks to the DPCD transactions in the SW link training
Signed-off-by: NSean Paul <seanpaul@chromium.org>
Signed-off-by: NJingoo Han <jg1.han@samsung.com>

drivers/video/exynos/exynos_dp_core.c

@@ -262,11 +262,10 @@ static void exynos_dp_set_lane_lane_pre_emphasis(struct exynos_dp_device *dp,
 	}
 }
 
-static void exynos_dp_link_start(struct exynos_dp_device *dp)
+static int exynos_dp_link_start(struct exynos_dp_device *dp)
 {
 	u8 buf[4];
-	int lane;
-	int lane_count;
+	int lane, lane_count, retval;
 
 	lane_count = dp->link_train.lane_count;
 
@@ -277,8 +276,10 @@ static void exynos_dp_link_start(struct exynos_dp_device *dp)
 		dp->link_train.cr_loop[lane] = 0;
 
 	/* Set sink to D0 (Sink Not Ready) mode. */
-	exynos_dp_write_byte_to_dpcd(dp, DPCD_ADDR_SINK_POWER_STATE,
+	retval = exynos_dp_write_byte_to_dpcd(dp, DPCD_ADDR_SINK_POWER_STATE,
 				DPCD_SET_POWER_STATE_D0);
+	if (retval)
+		return retval;
 
 	/* Set link rate and count as you want to establish*/
 	exynos_dp_set_link_bandwidth(dp, dp->link_train.link_rate);
@@ -287,8 +288,10 @@ static void exynos_dp_link_start(struct exynos_dp_device *dp)
 	/* Setup RX configuration */
 	buf[0] = dp->link_train.link_rate;
 	buf[1] = dp->link_train.lane_count;
-	exynos_dp_write_bytes_to_dpcd(dp, DPCD_ADDR_LINK_BW_SET,
+	retval = exynos_dp_write_bytes_to_dpcd(dp, DPCD_ADDR_LINK_BW_SET,
 				2, buf);
+	if (retval)
+		return retval;
 
 	/* Set TX pre-emphasis to minimum */
 	for (lane = 0; lane < lane_count; lane++)
@@ -307,9 +310,11 @@ static void exynos_dp_link_start(struct exynos_dp_device *dp)
 	for (lane = 0; lane < lane_count; lane++)
 		buf[lane] = DPCD_PRE_EMPHASIS_PATTERN2_LEVEL0 |
 			    DPCD_VOLTAGE_SWING_PATTERN1_LEVEL0;
-	exynos_dp_write_bytes_to_dpcd(dp,
+	retval = exynos_dp_write_bytes_to_dpcd(dp,
 		DPCD_ADDR_TRAINING_LANE0_SET,
 		lane_count, buf);
+
+	return retval;
 }
 
 static unsigned char exynos_dp_get_lane_status(u8 link_status[2], int lane)
@@ -431,8 +436,7 @@ static void exynos_dp_reduce_link_rate(struct exynos_dp_device *dp)
 static int exynos_dp_process_clock_recovery(struct exynos_dp_device *dp)
 {
 	u8 link_status[2];
-	int lane;
-	int lane_count;
+	int lane, lane_count, retval;
 
 	u8 adjust_request[2];
 	u8 voltage_swing;
@@ -443,17 +447,22 @@ static int exynos_dp_process_clock_recovery(struct exynos_dp_device *dp)
 
 	lane_count = dp->link_train.lane_count;
 
-	exynos_dp_read_bytes_from_dpcd(dp, DPCD_ADDR_LANE0_1_STATUS,
+	retval =  exynos_dp_read_bytes_from_dpcd(dp, DPCD_ADDR_LANE0_1_STATUS,
 				2, link_status);
+	if (retval)
+		return retval;
 
 	if (exynos_dp_clock_recovery_ok(link_status, lane_count) == 0) {
 		/* set training pattern 2 for EQ */
 		exynos_dp_set_training_pattern(dp, TRAINING_PTN2);
 
 		for (lane = 0; lane < lane_count; lane++) {
-			exynos_dp_read_bytes_from_dpcd(dp,
+			retval = exynos_dp_read_bytes_from_dpcd(dp,
 					DPCD_ADDR_ADJUST_REQUEST_LANE0_1,
 					2, adjust_request);
+			if (retval)
+				return retval;
+
 			voltage_swing = exynos_dp_get_adjust_request_voltage(
 							adjust_request, lane);
 			pre_emphasis = exynos_dp_get_adjust_request_pre_emphasis(
@@ -473,15 +482,19 @@ static int exynos_dp_process_clock_recovery(struct exynos_dp_device *dp)
 				lane);
 		}
 
-		exynos_dp_write_byte_to_dpcd(dp,
+		retval = exynos_dp_write_byte_to_dpcd(dp,
 			DPCD_ADDR_TRAINING_PATTERN_SET,
 			DPCD_SCRAMBLING_DISABLED |
 			DPCD_TRAINING_PATTERN_2);
+		if (retval)
+			return retval;
 
-		exynos_dp_write_bytes_to_dpcd(dp,
+		retval = exynos_dp_write_bytes_to_dpcd(dp,
 			DPCD_ADDR_TRAINING_LANE0_SET,
 			lane_count,
 			dp->link_train.training_lane);
+		if (retval)
+			return retval;
 
 		dev_info(dp->dev, "Link Training Clock Recovery success\n");
 		dp->link_train.lt_state = EQUALIZER_TRAINING;
@@ -489,9 +502,12 @@ static int exynos_dp_process_clock_recovery(struct exynos_dp_device *dp)
 		for (lane = 0; lane < lane_count; lane++) {
 			training_lane = exynos_dp_get_lane_link_training(
 							dp, lane);
-			exynos_dp_read_bytes_from_dpcd(dp,
+			retval = exynos_dp_read_bytes_from_dpcd(dp,
 					DPCD_ADDR_ADJUST_REQUEST_LANE0_1,
 					2, adjust_request);
+			if (retval)
+				return retval;
+
 			voltage_swing = exynos_dp_get_adjust_request_voltage(
 							adjust_request, lane);
 			pre_emphasis = exynos_dp_get_adjust_request_pre_emphasis(
@@ -528,13 +544,14 @@ static int exynos_dp_process_clock_recovery(struct exynos_dp_device *dp)
 				dp->link_train.training_lane[lane], lane);
 		}
 
-		exynos_dp_write_bytes_to_dpcd(dp,
-			DPCD_ADDR_TRAINING_LANE0_SET,
-			lane_count,
-			dp->link_train.training_lane);
+		retval = exynos_dp_write_bytes_to_dpcd(dp,
+				DPCD_ADDR_TRAINING_LANE0_SET, lane_count,
+				dp->link_train.training_lane);
+		if (retval)
+			return retval;
 	}
 
-	return 0;
+	return retval;
 
 reduce_link_rate:
 	exynos_dp_reduce_link_rate(dp);
@@ -545,8 +562,7 @@ static int exynos_dp_process_equalizer_training(struct exynos_dp_device *dp)
 {
 	u8 link_status[2];
 	u8 link_align[3];
-	int lane;
-	int lane_count;
+	int lane, lane_count, retval;
 	u32 reg;
 
 	u8 adjust_request[2];
@@ -558,8 +574,10 @@ static int exynos_dp_process_equalizer_training(struct exynos_dp_device *dp)
 
 	lane_count = dp->link_train.lane_count;
 
-	exynos_dp_read_bytes_from_dpcd(dp, DPCD_ADDR_LANE0_1_STATUS,
+	retval = exynos_dp_read_bytes_from_dpcd(dp, DPCD_ADDR_LANE0_1_STATUS,
 				2, link_status);
+	if (retval)
+		return retval;
 
 	if (exynos_dp_clock_recovery_ok(link_status, lane_count) == 0) {
 		link_align[0] = link_status[0];
@@ -570,9 +588,12 @@ static int exynos_dp_process_equalizer_training(struct exynos_dp_device *dp)
 			&link_align[2]);
 
 		for (lane = 0; lane < lane_count; lane++) {
-			exynos_dp_read_bytes_from_dpcd(dp,
+			retval = exynos_dp_read_bytes_from_dpcd(dp,
 					DPCD_ADDR_ADJUST_REQUEST_LANE0_1,
 					2, adjust_request);
+			if (retval)
+				return retval;
+
 			voltage_swing = exynos_dp_get_adjust_request_voltage(
 							adjust_request, lane);
 			pre_emphasis = exynos_dp_get_adjust_request_pre_emphasis(
@@ -621,10 +642,12 @@ static int exynos_dp_process_equalizer_training(struct exynos_dp_device *dp)
 					dp->link_train.training_lane[lane],
 					lane);
 
-			exynos_dp_write_bytes_to_dpcd(dp,
-				DPCD_ADDR_TRAINING_LANE0_SET,
-				lane_count,
-				dp->link_train.training_lane);
+			retval = exynos_dp_write_bytes_to_dpcd(dp,
+					DPCD_ADDR_TRAINING_LANE0_SET,
+					lane_count,
+					dp->link_train.training_lane);
+			if (retval)
+				return retval;
 		}
 	} else {
 		goto reduce_link_rate;
@@ -702,16 +725,17 @@ static void exynos_dp_init_training(struct exynos_dp_device *dp,
 
 static int exynos_dp_sw_link_training(struct exynos_dp_device *dp)
 {
-	int retval = 0;
-	int training_finished = 0;
+	int retval = 0, training_finished = 0;
 
 	dp->link_train.lt_state = START;
 
 	/* Process here */
-	while (!training_finished) {
+	while (!retval && !training_finished) {
 		switch (dp->link_train.lt_state) {
 		case START:
-			exynos_dp_link_start(dp);
+			retval = exynos_dp_link_start(dp);
+			if (retval)
+				dev_err(dp->dev, "LT link start failed!\n");
 			break;
 		case CLOCK_RECOVERY:
 			retval = exynos_dp_process_clock_recovery(dp);
@@ -730,6 +754,8 @@ static int exynos_dp_sw_link_training(struct exynos_dp_device *dp)
 			return -EREMOTEIO;
 		}
 	}
+	if (retval)
+		dev_err(dp->dev, "eDP link training failed (%d)\n", retval);
 
 	return retval;
 }