[v4,11/11] drm/i915: Implement Link Rate fallback on Link training failure

Submitted by Jani Nikula on April 6, 2017, 1:44 p.m.

Details

Message ID 16ca48b1e74c618929245e9a085b9e3483c3a16d.1491485983.git.jani.nikula@intel.com
State New
Headers show
Series "drm/i915/dp: rest of refactoring, link rate fallback" ( rev: 3 2 1 ) in Intel GFX

Not browsing as part of any series.

Commit Message

Jani Nikula April 6, 2017, 1:44 p.m.
From: Manasi Navare <manasi.d.navare@intel.com>

If link training at a link rate optimal for a particular
mode fails during modeset's atomic commit phase, then we
let the modeset complete and then retry. We save the link rate
value at which link training failed, update the link status property
to "BAD" and use a lower link rate to prune the modes. It will redo
the modeset on the current mode at lower link rate or if the current
mode gets pruned due to lower link constraints then, it will send a
hotplug uevent for userspace to handle it.

This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
4.3.1.6.

This patch is a resend of the original commit id (233ce881dd91fb
"drm/i915: Implement Link Rate fallback on Link training failure")
which got reverted in this commit id (afc1ebf4562a14 Revert
"drm/i915: Implement Link Rate fallback on Link training failure")
due to CI failures.

After investigating the CI failures it was found that these
were essentially the failures which were always there but hidden because
they used to be DRM_DEBUG_KMS messages for link failures so never got
caught by CI. But now this patch actually throws DRM_ERROR if the link
training fails at RBR and 1 lane. So it caught these link train failures.

There were two failures:
1. On SKL 6700k this was because the machine in CI lab is a SKL desktop
without eDP on Port A. But our VBT initialization code in the driver writes
VBT defaults in a way that it always sets DP flag on Port A and this does
not get cleared after parsing the VBT outputs. This has been fixed in
commit id (bb1d132935c2f8 "drm/i915/vbt: split out defaults that are set
when there is no VBT) and (665788572c6410b "drm/i915/vbt: don't propagate
errors from intel_bios_init())

2. On ILK-650 desktop - This was happening because of a bad monitor desktop
combination. I switched the monitor in the CI lab and that helped get rid
of the link failures on ILK system.

v10:
* Rebase on drm-tip and resend after revert
v9:
* Use the trimmed max values of link rate/lane count based on
link train fallback (Daniel Vetter)
v8:
* Set link_status to BAD first and then call mode_valid (Jani Nikula)
v7:
Remove the redundant variable in previous patch itself
v6:
* Obtain link rate index from fallback_link_rate using
the helper intel_dp_link_rate_index (Jani Nikula)
* Include fallback within intel_dp_start_link_train (Jani Nikula)
v5:
* Move set link status to drm core (Daniel Vetter, Jani Nikula)
v4:
* Add fallback support for non DDI platforms too
* Set connector->link status inside set_link_status function
(Jani Nikula)
v3:
* Set link status property to BAd unconditionally (Jani Nikula)
* Dont use two separate variables link_train_failed and link_status
to indicate same thing (Jani Nikula)
v2:
* Squashed a few patches (Jani Nikula)

Acked-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <Harry.wentland@amd.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c               | 27 +++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_dp_link_training.c | 22 ++++++++++++++++++++--
 drivers/gpu/drm/i915/intel_drv.h              |  3 +++
 3 files changed, 50 insertions(+), 2 deletions(-)

Patch hide | download patch | download mbox

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 6915d89a238c..f2d792a1b18e 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -5977,6 +5977,29 @@  intel_dp_init_connector_port_info(struct intel_digital_port *intel_dig_port)
 	}
 }
 
+static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
+{
+	struct intel_connector *intel_connector;
+	struct drm_connector *connector;
+
+	intel_connector = container_of(work, typeof(*intel_connector),
+				       modeset_retry_work);
+	connector = &intel_connector->base;
+	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
+		      connector->name);
+
+	/* Grab the locks before changing connector property*/
+	mutex_lock(&connector->dev->mode_config.mutex);
+	/* Set connector link status to BAD and send a Uevent to notify
+	 * userspace to do a modeset.
+	 */
+	drm_mode_connector_set_link_status_property(connector,
+						    DRM_MODE_LINK_STATUS_BAD);
+	mutex_unlock(&connector->dev->mode_config.mutex);
+	/* Send Hotplug uevent so userspace can reprobe */
+	drm_kms_helper_hotplug_event(connector->dev);
+}
+
 bool
 intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 			struct intel_connector *intel_connector)
@@ -5989,6 +6012,10 @@  intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 	enum port port = intel_dig_port->port;
 	int type;
 
+	/* Initialize the work for modeset in case of link train failure */
+	INIT_WORK(&intel_connector->modeset_retry_work,
+		  intel_dp_modeset_retry_work_fn);
+
 	if (WARN(intel_dig_port->max_lanes < 1,
 		 "Not enough lanes (%d) for DP on port %c\n",
 		 intel_dig_port->max_lanes, port_name(port)))
diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
index 694ad0ffb523..b79c1c0e404c 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -314,6 +314,24 @@  void intel_dp_stop_link_train(struct intel_dp *intel_dp)
 void
 intel_dp_start_link_train(struct intel_dp *intel_dp)
 {
-	intel_dp_link_training_clock_recovery(intel_dp);
-	intel_dp_link_training_channel_equalization(intel_dp);
+	struct intel_connector *intel_connector = intel_dp->attached_connector;
+
+	if (!intel_dp_link_training_clock_recovery(intel_dp))
+		goto failure_handling;
+	if (!intel_dp_link_training_channel_equalization(intel_dp))
+		goto failure_handling;
+
+	DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
+		      intel_dp->link_rate, intel_dp->lane_count);
+	return;
+
+ failure_handling:
+	DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
+		      intel_dp->link_rate, intel_dp->lane_count);
+	if (!intel_dp_get_link_train_fallback_values(intel_dp,
+						     intel_dp->link_rate,
+						     intel_dp->lane_count))
+		/* Schedule a Hotplug Uevent to userspace to start modeset */
+		schedule_work(&intel_connector->modeset_retry_work);
+	return;
 }
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 5f6e1aad909d..d36026eff7cd 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -321,6 +321,9 @@  struct intel_connector {
 	void *port; /* store this opaque as its illegal to dereference it */
 
 	struct intel_dp *mst_port;
+
+	/* Work struct to schedule a uevent on link train failure */
+	struct work_struct modeset_retry_work;
 };
 
 struct dpll {

Comments

Hi Jani,

This patch has the necessary ACKs and R-bs, anything else
blocking this from getting merged?

Regards
Manasi

On Thu, Apr 06, 2017 at 04:44:19PM +0300, Jani Nikula wrote:
> From: Manasi Navare <manasi.d.navare@intel.com>
> 
> If link training at a link rate optimal for a particular
> mode fails during modeset's atomic commit phase, then we
> let the modeset complete and then retry. We save the link rate
> value at which link training failed, update the link status property
> to "BAD" and use a lower link rate to prune the modes. It will redo
> the modeset on the current mode at lower link rate or if the current
> mode gets pruned due to lower link constraints then, it will send a
> hotplug uevent for userspace to handle it.
> 
> This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
> 4.3.1.6.
> 
> This patch is a resend of the original commit id (233ce881dd91fb
> "drm/i915: Implement Link Rate fallback on Link training failure")
> which got reverted in this commit id (afc1ebf4562a14 Revert
> "drm/i915: Implement Link Rate fallback on Link training failure")
> due to CI failures.
> 
> After investigating the CI failures it was found that these
> were essentially the failures which were always there but hidden because
> they used to be DRM_DEBUG_KMS messages for link failures so never got
> caught by CI. But now this patch actually throws DRM_ERROR if the link
> training fails at RBR and 1 lane. So it caught these link train failures.
> 
> There were two failures:
> 1. On SKL 6700k this was because the machine in CI lab is a SKL desktop
> without eDP on Port A. But our VBT initialization code in the driver writes
> VBT defaults in a way that it always sets DP flag on Port A and this does
> not get cleared after parsing the VBT outputs. This has been fixed in
> commit id (bb1d132935c2f8 "drm/i915/vbt: split out defaults that are set
> when there is no VBT) and (665788572c6410b "drm/i915/vbt: don't propagate
> errors from intel_bios_init())
> 
> 2. On ILK-650 desktop - This was happening because of a bad monitor desktop
> combination. I switched the monitor in the CI lab and that helped get rid
> of the link failures on ILK system.
> 
> v10:
> * Rebase on drm-tip and resend after revert
> v9:
> * Use the trimmed max values of link rate/lane count based on
> link train fallback (Daniel Vetter)
> v8:
> * Set link_status to BAD first and then call mode_valid (Jani Nikula)
> v7:
> Remove the redundant variable in previous patch itself
> v6:
> * Obtain link rate index from fallback_link_rate using
> the helper intel_dp_link_rate_index (Jani Nikula)
> * Include fallback within intel_dp_start_link_train (Jani Nikula)
> v5:
> * Move set link status to drm core (Daniel Vetter, Jani Nikula)
> v4:
> * Add fallback support for non DDI platforms too
> * Set connector->link status inside set_link_status function
> (Jani Nikula)
> v3:
> * Set link status property to BAd unconditionally (Jani Nikula)
> * Dont use two separate variables link_train_failed and link_status
> to indicate same thing (Jani Nikula)
> v2:
> * Squashed a few patches (Jani Nikula)
> 
> Acked-by: Tony Cheng <tony.cheng@amd.com>
> Acked-by: Harry Wentland <Harry.wentland@amd.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c               | 27 +++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_dp_link_training.c | 22 ++++++++++++++++++++--
>  drivers/gpu/drm/i915/intel_drv.h              |  3 +++
>  3 files changed, 50 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 6915d89a238c..f2d792a1b18e 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5977,6 +5977,29 @@ intel_dp_init_connector_port_info(struct intel_digital_port *intel_dig_port)
>  	}
>  }
>  
> +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> +{
> +	struct intel_connector *intel_connector;
> +	struct drm_connector *connector;
> +
> +	intel_connector = container_of(work, typeof(*intel_connector),
> +				       modeset_retry_work);
> +	connector = &intel_connector->base;
> +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> +		      connector->name);
> +
> +	/* Grab the locks before changing connector property*/
> +	mutex_lock(&connector->dev->mode_config.mutex);
> +	/* Set connector link status to BAD and send a Uevent to notify
> +	 * userspace to do a modeset.
> +	 */
> +	drm_mode_connector_set_link_status_property(connector,
> +						    DRM_MODE_LINK_STATUS_BAD);
> +	mutex_unlock(&connector->dev->mode_config.mutex);
> +	/* Send Hotplug uevent so userspace can reprobe */
> +	drm_kms_helper_hotplug_event(connector->dev);
> +}
> +
>  bool
>  intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  			struct intel_connector *intel_connector)
> @@ -5989,6 +6012,10 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  	enum port port = intel_dig_port->port;
>  	int type;
>  
> +	/* Initialize the work for modeset in case of link train failure */
> +	INIT_WORK(&intel_connector->modeset_retry_work,
> +		  intel_dp_modeset_retry_work_fn);
> +
>  	if (WARN(intel_dig_port->max_lanes < 1,
>  		 "Not enough lanes (%d) for DP on port %c\n",
>  		 intel_dig_port->max_lanes, port_name(port)))
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index 694ad0ffb523..b79c1c0e404c 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -314,6 +314,24 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
>  void
>  intel_dp_start_link_train(struct intel_dp *intel_dp)
>  {
> -	intel_dp_link_training_clock_recovery(intel_dp);
> -	intel_dp_link_training_channel_equalization(intel_dp);
> +	struct intel_connector *intel_connector = intel_dp->attached_connector;
> +
> +	if (!intel_dp_link_training_clock_recovery(intel_dp))
> +		goto failure_handling;
> +	if (!intel_dp_link_training_channel_equalization(intel_dp))
> +		goto failure_handling;
> +
> +	DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> +		      intel_dp->link_rate, intel_dp->lane_count);
> +	return;
> +
> + failure_handling:
> +	DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> +		      intel_dp->link_rate, intel_dp->lane_count);
> +	if (!intel_dp_get_link_train_fallback_values(intel_dp,
> +						     intel_dp->link_rate,
> +						     intel_dp->lane_count))
> +		/* Schedule a Hotplug Uevent to userspace to start modeset */
> +		schedule_work(&intel_connector->modeset_retry_work);
> +	return;
>  }
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 5f6e1aad909d..d36026eff7cd 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -321,6 +321,9 @@ struct intel_connector {
>  	void *port; /* store this opaque as its illegal to dereference it */
>  
>  	struct intel_dp *mst_port;
> +
> +	/* Work struct to schedule a uevent on link train failure */
> +	struct work_struct modeset_retry_work;
>  };
>  
>  struct dpll {
> -- 
> 2.1.4
>
On Thu, 13 Apr 2017, Manasi Navare <manasi.d.navare@intel.com> wrote:
> Hi Jani,
>
> This patch has the necessary ACKs and R-bs, anything else
> blocking this from getting merged?

Pushed, finally, sorry for the delay.

BR,
Jani.

>
> Regards
> Manasi
>
> On Thu, Apr 06, 2017 at 04:44:19PM +0300, Jani Nikula wrote:
>> From: Manasi Navare <manasi.d.navare@intel.com>
>> 
>> If link training at a link rate optimal for a particular
>> mode fails during modeset's atomic commit phase, then we
>> let the modeset complete and then retry. We save the link rate
>> value at which link training failed, update the link status property
>> to "BAD" and use a lower link rate to prune the modes. It will redo
>> the modeset on the current mode at lower link rate or if the current
>> mode gets pruned due to lower link constraints then, it will send a
>> hotplug uevent for userspace to handle it.
>> 
>> This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
>> 4.3.1.6.
>> 
>> This patch is a resend of the original commit id (233ce881dd91fb
>> "drm/i915: Implement Link Rate fallback on Link training failure")
>> which got reverted in this commit id (afc1ebf4562a14 Revert
>> "drm/i915: Implement Link Rate fallback on Link training failure")
>> due to CI failures.
>> 
>> After investigating the CI failures it was found that these
>> were essentially the failures which were always there but hidden because
>> they used to be DRM_DEBUG_KMS messages for link failures so never got
>> caught by CI. But now this patch actually throws DRM_ERROR if the link
>> training fails at RBR and 1 lane. So it caught these link train failures.
>> 
>> There were two failures:
>> 1. On SKL 6700k this was because the machine in CI lab is a SKL desktop
>> without eDP on Port A. But our VBT initialization code in the driver writes
>> VBT defaults in a way that it always sets DP flag on Port A and this does
>> not get cleared after parsing the VBT outputs. This has been fixed in
>> commit id (bb1d132935c2f8 "drm/i915/vbt: split out defaults that are set
>> when there is no VBT) and (665788572c6410b "drm/i915/vbt: don't propagate
>> errors from intel_bios_init())
>> 
>> 2. On ILK-650 desktop - This was happening because of a bad monitor desktop
>> combination. I switched the monitor in the CI lab and that helped get rid
>> of the link failures on ILK system.
>> 
>> v10:
>> * Rebase on drm-tip and resend after revert
>> v9:
>> * Use the trimmed max values of link rate/lane count based on
>> link train fallback (Daniel Vetter)
>> v8:
>> * Set link_status to BAD first and then call mode_valid (Jani Nikula)
>> v7:
>> Remove the redundant variable in previous patch itself
>> v6:
>> * Obtain link rate index from fallback_link_rate using
>> the helper intel_dp_link_rate_index (Jani Nikula)
>> * Include fallback within intel_dp_start_link_train (Jani Nikula)
>> v5:
>> * Move set link status to drm core (Daniel Vetter, Jani Nikula)
>> v4:
>> * Add fallback support for non DDI platforms too
>> * Set connector->link status inside set_link_status function
>> (Jani Nikula)
>> v3:
>> * Set link status property to BAd unconditionally (Jani Nikula)
>> * Dont use two separate variables link_train_failed and link_status
>> to indicate same thing (Jani Nikula)
>> v2:
>> * Squashed a few patches (Jani Nikula)
>> 
>> Acked-by: Tony Cheng <tony.cheng@amd.com>
>> Acked-by: Harry Wentland <Harry.wentland@amd.com>
>> Cc: Jani Nikula <jani.nikula@linux.intel.com>
>> Cc: Daniel Vetter <daniel.vetter@intel.com>
>> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
>> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
>> Reviewed-by: Jani Nikula <jani.nikula@intel.com>
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>> ---
>>  drivers/gpu/drm/i915/intel_dp.c               | 27 +++++++++++++++++++++++++++
>>  drivers/gpu/drm/i915/intel_dp_link_training.c | 22 ++++++++++++++++++++--
>>  drivers/gpu/drm/i915/intel_drv.h              |  3 +++
>>  3 files changed, 50 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index 6915d89a238c..f2d792a1b18e 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -5977,6 +5977,29 @@ intel_dp_init_connector_port_info(struct intel_digital_port *intel_dig_port)
>>  	}
>>  }
>>  
>> +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
>> +{
>> +	struct intel_connector *intel_connector;
>> +	struct drm_connector *connector;
>> +
>> +	intel_connector = container_of(work, typeof(*intel_connector),
>> +				       modeset_retry_work);
>> +	connector = &intel_connector->base;
>> +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
>> +		      connector->name);
>> +
>> +	/* Grab the locks before changing connector property*/
>> +	mutex_lock(&connector->dev->mode_config.mutex);
>> +	/* Set connector link status to BAD and send a Uevent to notify
>> +	 * userspace to do a modeset.
>> +	 */
>> +	drm_mode_connector_set_link_status_property(connector,
>> +						    DRM_MODE_LINK_STATUS_BAD);
>> +	mutex_unlock(&connector->dev->mode_config.mutex);
>> +	/* Send Hotplug uevent so userspace can reprobe */
>> +	drm_kms_helper_hotplug_event(connector->dev);
>> +}
>> +
>>  bool
>>  intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>>  			struct intel_connector *intel_connector)
>> @@ -5989,6 +6012,10 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>>  	enum port port = intel_dig_port->port;
>>  	int type;
>>  
>> +	/* Initialize the work for modeset in case of link train failure */
>> +	INIT_WORK(&intel_connector->modeset_retry_work,
>> +		  intel_dp_modeset_retry_work_fn);
>> +
>>  	if (WARN(intel_dig_port->max_lanes < 1,
>>  		 "Not enough lanes (%d) for DP on port %c\n",
>>  		 intel_dig_port->max_lanes, port_name(port)))
>> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
>> index 694ad0ffb523..b79c1c0e404c 100644
>> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
>> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
>> @@ -314,6 +314,24 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
>>  void
>>  intel_dp_start_link_train(struct intel_dp *intel_dp)
>>  {
>> -	intel_dp_link_training_clock_recovery(intel_dp);
>> -	intel_dp_link_training_channel_equalization(intel_dp);
>> +	struct intel_connector *intel_connector = intel_dp->attached_connector;
>> +
>> +	if (!intel_dp_link_training_clock_recovery(intel_dp))
>> +		goto failure_handling;
>> +	if (!intel_dp_link_training_channel_equalization(intel_dp))
>> +		goto failure_handling;
>> +
>> +	DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
>> +		      intel_dp->link_rate, intel_dp->lane_count);
>> +	return;
>> +
>> + failure_handling:
>> +	DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
>> +		      intel_dp->link_rate, intel_dp->lane_count);
>> +	if (!intel_dp_get_link_train_fallback_values(intel_dp,
>> +						     intel_dp->link_rate,
>> +						     intel_dp->lane_count))
>> +		/* Schedule a Hotplug Uevent to userspace to start modeset */
>> +		schedule_work(&intel_connector->modeset_retry_work);
>> +	return;
>>  }
>> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>> index 5f6e1aad909d..d36026eff7cd 100644
>> --- a/drivers/gpu/drm/i915/intel_drv.h
>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>> @@ -321,6 +321,9 @@ struct intel_connector {
>>  	void *port; /* store this opaque as its illegal to dereference it */
>>  
>>  	struct intel_dp *mst_port;
>> +
>> +	/* Work struct to schedule a uevent on link train failure */
>> +	struct work_struct modeset_retry_work;
>>  };
>>  
>>  struct dpll {
>> -- 
>> 2.1.4
>>