[PATCH] drm/i915: Revert DisplayPort fast link training feature

[PATCH] drm/i915: Revert DisplayPort fast link training feature

[Mika Kahola]

It has been turned out that in some HW combination the DisplayPort
fast link training feature caused screen flickering. Let's revert
this feature for now until we can ensure that the feature works for
all platforms.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91393
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c               |  3 ---
 drivers/gpu/drm/i915/intel_dp_link_training.c | 26 ++------------------------
 drivers/gpu/drm/i915/intel_drv.h              |  2 --
 3 files changed, 2 insertions(+), 29 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index be08351..3cdea4d7a 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4621,9 +4621,6 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
 	intel_display_power_get(dev_priv, power_domain);
 
 	if (long_hpd) {
-		/* indicate that we need to restart link training */
-		intel_dp->train_set_valid = false;
-
 		intel_dp_long_pulse(intel_dp->attached_connector);
 		if (intel_dp->is_mst)
 			ret = IRQ_HANDLED;
diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
index 0b8eefc..60fb39c 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -85,8 +85,7 @@ static bool
 intel_dp_reset_link_train(struct intel_dp *intel_dp,
 			uint8_t dp_train_pat)
 {
-	if (!intel_dp->train_set_valid)
-		memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
+	memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
 	intel_dp_set_signal_levels(intel_dp);
 	return intel_dp_set_link_train(intel_dp, dp_train_pat);
 }
@@ -161,23 +160,6 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
 			break;
 		}
 
-		/*
-		 * if we used previously trained voltage and pre-emphasis values
-		 * and we don't get clock recovery, reset link training values
-		 */
-		if (intel_dp->train_set_valid) {
-			DRM_DEBUG_KMS("clock recovery not ok, reset");
-			/* clear the flag as we are not reusing train set */
-			intel_dp->train_set_valid = false;
-			if (!intel_dp_reset_link_train(intel_dp,
-						       DP_TRAINING_PATTERN_1 |
-						       DP_LINK_SCRAMBLING_DISABLE)) {
-				DRM_ERROR("failed to enable link training\n");
-				return;
-			}
-			continue;
-		}
-
 		/* Check to see if we've tried the max voltage */
 		for (i = 0; i < intel_dp->lane_count; i++)
 			if ((intel_dp->train_set[i] & DP_TRAIN_MAX_SWING_REACHED) == 0)
@@ -284,7 +266,6 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
 		/* Make sure clock is still ok */
 		if (!drm_dp_clock_recovery_ok(link_status,
 					      intel_dp->lane_count)) {
-			intel_dp->train_set_valid = false;
 			intel_dp_link_training_clock_recovery(intel_dp);
 			intel_dp_set_link_train(intel_dp,
 						training_pattern |
@@ -301,7 +282,6 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
 
 		/* Try 5 times, then try clock recovery if that fails */
 		if (tries > 5) {
-			intel_dp->train_set_valid = false;
 			intel_dp_link_training_clock_recovery(intel_dp);
 			intel_dp_set_link_train(intel_dp,
 						training_pattern |
@@ -322,10 +302,8 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
 
 	intel_dp_set_idle_link_train(intel_dp);
 
-	if (channel_eq) {
-		intel_dp->train_set_valid = true;
+	if (channel_eq)
 		DRM_DEBUG_KMS("Channel EQ done. DP Training successful\n");
-	}
 }
 
 void intel_dp_stop_link_train(struct intel_dp *intel_dp)
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 0c1dc9b..9257f08 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -894,8 +894,6 @@ struct intel_dp {
 	/* This is called before a link training is starterd */
 	void (*prepare_link_retrain)(struct intel_dp *intel_dp);
 
-	bool train_set_valid;
-
 	/* Displayport compliance testing */
 	unsigned long compliance_test_type;
 	unsigned long compliance_test_data;
-- 
1.9.1

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✓ Ro.CI.BAT: success for drm/i915: Revert DisplayPort fast link training feature

[Patchwork]

== Series Details ==

Series: drm/i915: Revert DisplayPort fast link training feature
URL   : https://patchwork.freedesktop.org/series/8828/
State : success

== Summary ==

Series 8828v1 drm/i915: Revert DisplayPort fast link training feature
http://patchwork.freedesktop.org/api/1.0/series/8828/revisions/1/mbox


fi-snb-i7-2600   total:213  pass:174  dwarn:0   dfail:0   fail:0   skip:39 
ro-bdw-i5-5250u  total:213  pass:197  dwarn:1   dfail:0   fail:0   skip:15 
ro-bdw-i7-5600u  total:213  pass:185  dwarn:0   dfail:0   fail:0   skip:28 
ro-bsw-n3050     total:213  pass:172  dwarn:0   dfail:0   fail:2   skip:39 
ro-byt-n2820     total:213  pass:173  dwarn:0   dfail:0   fail:3   skip:37 
ro-hsw-i3-4010u  total:213  pass:190  dwarn:0   dfail:0   fail:0   skip:23 
ro-hsw-i7-4770r  total:213  pass:190  dwarn:0   dfail:0   fail:0   skip:23 
ro-ilk-i7-620lm  total:213  pass:150  dwarn:0   dfail:0   fail:1   skip:62 
ro-ilk1-i5-650   total:208  pass:150  dwarn:0   dfail:0   fail:1   skip:57 
ro-ivb-i7-3770   total:213  pass:181  dwarn:0   dfail:0   fail:0   skip:32 
ro-ivb2-i7-3770  total:213  pass:185  dwarn:0   dfail:0   fail:0   skip:28 
ro-skl3-i5-6260u total:213  pass:201  dwarn:1   dfail:0   fail:0   skip:11 
ro-snb-i7-2620M  total:213  pass:174  dwarn:0   dfail:0   fail:1   skip:38 
fi-hsw-i7-4770k failed to connect after reboot
fi-skl-i5-6260u failed to connect after reboot
fi-skl-i7-6700k failed to connect after reboot

Results at /archive/results/CI_IGT_test/RO_Patchwork_1210/

828cccf drm-intel-nightly: 2016y-06m-17d-09h-38m-29s UTC integration manifest
f7779be drm/i915: Revert DisplayPort fast link training feature

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Re: [PATCH] drm/i915: Revert DisplayPort fast link training feature

[Jani Nikula]

On Fri, 17 Jun 2016, Mika Kahola <mika.kahola@intel.com> wrote:
> It has been turned out that in some HW combination the DisplayPort

"It has turned out" or "It has been found out", I think.

> fast link training feature caused screen flickering. Let's revert
> this feature for now until we can ensure that the feature works for
> all platforms.

Please add this to the commit message:

This is a manual revert of commits 5fa836a9d859 ("drm/i915: DP link
training optimization") and 4e96c97742f4 ("drm/i915: eDP link training
optimization").

Fixes: 5fa836a9d859 ("drm/i915: DP link training optimization")
Fixes: 4e96c97742f4 ("drm/i915: eDP link training optimization")
Cc: stable@vger.kernel.org # v4.2+
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91393
> Signed-off-by: Mika Kahola <mika.kahola@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c               |  3 ---
>  drivers/gpu/drm/i915/intel_dp_link_training.c | 26 ++------------------------
>  drivers/gpu/drm/i915/intel_drv.h              |  2 --
>  3 files changed, 2 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index be08351..3cdea4d7a 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4621,9 +4621,6 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
>  	intel_display_power_get(dev_priv, power_domain);
>  
>  	if (long_hpd) {
> -		/* indicate that we need to restart link training */
> -		intel_dp->train_set_valid = false;
> -
>  		intel_dp_long_pulse(intel_dp->attached_connector);
>  		if (intel_dp->is_mst)
>  			ret = IRQ_HANDLED;
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index 0b8eefc..60fb39c 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -85,8 +85,7 @@ static bool
>  intel_dp_reset_link_train(struct intel_dp *intel_dp,
>  			uint8_t dp_train_pat)
>  {
> -	if (!intel_dp->train_set_valid)
> -		memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
> +	memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
>  	intel_dp_set_signal_levels(intel_dp);
>  	return intel_dp_set_link_train(intel_dp, dp_train_pat);
>  }
> @@ -161,23 +160,6 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
>  			break;
>  		}
>  
> -		/*
> -		 * if we used previously trained voltage and pre-emphasis values
> -		 * and we don't get clock recovery, reset link training values
> -		 */
> -		if (intel_dp->train_set_valid) {
> -			DRM_DEBUG_KMS("clock recovery not ok, reset");
> -			/* clear the flag as we are not reusing train set */
> -			intel_dp->train_set_valid = false;
> -			if (!intel_dp_reset_link_train(intel_dp,
> -						       DP_TRAINING_PATTERN_1 |
> -						       DP_LINK_SCRAMBLING_DISABLE)) {
> -				DRM_ERROR("failed to enable link training\n");
> -				return;
> -			}
> -			continue;
> -		}
> -
>  		/* Check to see if we've tried the max voltage */
>  		for (i = 0; i < intel_dp->lane_count; i++)
>  			if ((intel_dp->train_set[i] & DP_TRAIN_MAX_SWING_REACHED) == 0)
> @@ -284,7 +266,6 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
>  		/* Make sure clock is still ok */
>  		if (!drm_dp_clock_recovery_ok(link_status,
>  					      intel_dp->lane_count)) {
> -			intel_dp->train_set_valid = false;
>  			intel_dp_link_training_clock_recovery(intel_dp);
>  			intel_dp_set_link_train(intel_dp,
>  						training_pattern |
> @@ -301,7 +282,6 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
>  
>  		/* Try 5 times, then try clock recovery if that fails */
>  		if (tries > 5) {
> -			intel_dp->train_set_valid = false;
>  			intel_dp_link_training_clock_recovery(intel_dp);
>  			intel_dp_set_link_train(intel_dp,
>  						training_pattern |
> @@ -322,10 +302,8 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
>  
>  	intel_dp_set_idle_link_train(intel_dp);
>  
> -	if (channel_eq) {
> -		intel_dp->train_set_valid = true;
> +	if (channel_eq)
>  		DRM_DEBUG_KMS("Channel EQ done. DP Training successful\n");
> -	}
>  }
>  
>  void intel_dp_stop_link_train(struct intel_dp *intel_dp)
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 0c1dc9b..9257f08 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -894,8 +894,6 @@ struct intel_dp {
>  	/* This is called before a link training is starterd */
>  	void (*prepare_link_retrain)(struct intel_dp *intel_dp);
>  
> -	bool train_set_valid;
> -
>  	/* Displayport compliance testing */
>  	unsigned long compliance_test_type;
>  	unsigned long compliance_test_data;

-- 
Jani Nikula, Intel Open Source Technology Center
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