From 0df62823630d03d58f6eedb99fab285f847e4a1b Mon Sep 17 00:00:00 2001
From: George Shen <george.shen@amd.com>
Date: Fri, 15 Nov 2019 18:56:57 -0500
Subject: drm/amd/display: Increase the number of retries after AUX DEFER
Git-commit: 0df62823630d03d58f6eedb99fab285f847e4a1b
Patch-mainline: v5.5-rc2
References: bsc#1152472

[Why]
When a timeout occurs after a DEFER, some devices require more retries
than in the case of a regular timeout.

[How]
In a timeout occurrence, check whether a DEFER has occurred before the
timeout and retry MAX_DEFER_RETRIES retries times instead of
MAX_TIMEOUT_RETRIES.

Signed-off-by: George Shen <george.shen@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Abdoulaye Berthe <Abdoulaye.Berthe@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/amd/display/dc/dce/dce_aux.c | 32 ++++++++++++++------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
index e472608faf33..46a603bfa4bd 100644
--- a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
@@ -583,6 +583,8 @@ bool dce_aux_transfer_with_retries(struct ddc_service *ddc,
 	uint8_t reply;
 	bool payload_reply = true;
 	enum aux_channel_operation_result operation_result;
+	bool retry_on_defer = false;
+
 	int aux_ack_retries = 0,
 		aux_defer_retries = 0,
 		aux_i2c_defer_retries = 0,
@@ -613,8 +615,9 @@ bool dce_aux_transfer_with_retries(struct ddc_service *ddc,
 			break;
 
 			case AUX_TRANSACTION_REPLY_AUX_DEFER:
-			case AUX_TRANSACTION_REPLY_I2C_OVER_AUX_NACK:
 			case AUX_TRANSACTION_REPLY_I2C_OVER_AUX_DEFER:
+				retry_on_defer = true;
+			case AUX_TRANSACTION_REPLY_I2C_OVER_AUX_NACK:
 				if (++aux_defer_retries >= AUX_MAX_DEFER_RETRIES) {
 					goto fail;
 				} else {
@@ -647,15 +650,24 @@ bool dce_aux_transfer_with_retries(struct ddc_service *ddc,
 			break;
 
 		case AUX_CHANNEL_OPERATION_FAILED_TIMEOUT:
-			if (++aux_timeout_retries >= AUX_MAX_TIMEOUT_RETRIES)
-				goto fail;
-			else {
-				/*
-				 * DP 1.4, 2.8.2:  AUX Transaction Response/Reply Timeouts
-				 * According to the DP spec there should be 3 retries total
-				 * with a 400us wait inbetween each. Hardware already waits
-				 * for 550us therefore no wait is required here.
-				 */
+			// Check whether a DEFER had occurred before the timeout.
+			// If so, treat timeout as a DEFER.
+			if (retry_on_defer) {
+				if (++aux_defer_retries >= AUX_MAX_DEFER_RETRIES)
+					goto fail;
+				else if (payload->defer_delay > 0)
+					msleep(payload->defer_delay);
+			} else {
+				if (++aux_timeout_retries >= AUX_MAX_TIMEOUT_RETRIES)
+					goto fail;
+				else {
+					/*
+					 * DP 1.4, 2.8.2:  AUX Transaction Response/Reply Timeouts
+					 * According to the DP spec there should be 3 retries total
+					 * with a 400us wait inbetween each. Hardware already waits
+					 * for 550us therefore no wait is required here.
+					 */
+				}
 			}
 			break;
 
-- 
2.28.0