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

[Jani Nikula <jani.nikula@intel.com>]

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
>> 

-- 
Jani Nikula, Intel Open Source Technology Center
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