Re: [PATCH v10] drm/i915: Implement Link Rate fallback on Link training failure

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On Fri, 31 Mar 2017, Manasi Navare <manasi.d.navare@xxxxxxxxx> wrote:
> Hi Jani,
>
> I have reviewed your recent DP link rate / lane count
> refactoring patch series and I believe that it will soon get merged.

I haven't received reviews on all of the patches in my series yet, in
particular the first patches are missing reviews so I can't even get
started pushing them.

BR,
Jani.


>
> Are you waiting on merging this patch so that your refactoring
> series gets merged first? Or can we merge this patch since
> it already has ACKs and R-bs.
>
> Please advise on next steps for this patch, since some
> of the PSR related patches are pending merge because of this.
>
> Regards
> Manasi
>
>
> On Wed, Mar 22, 2017 at 08:44:36AM -0700, Manasi Navare wrote:
>> Hi Jani/Ville,
>> 
>> I need to add another quick fix which would be required for the fallback
>> to happen as expected. Should I respin this patch to add that fix or
>> should I wait for this to get landed?
>> 
>> I have mentioned the fix suggested below, please let me know your thoughts on that.
>> 
>> 
>> On Tue, Mar 14, 2017 at 03:11:51PM -0700, Manasi Navare wrote:
>> > 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@xxxxxxx>
>> > Acked-by: Harry Wentland <Harry.wentland@xxxxxxx>
>> > Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
>> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
>> > Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
>> > Signed-off-by: Manasi Navare <manasi.d.navare@xxxxxxxxx>
>> > Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx>
>> > Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
>> > ---
>> >  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 fd96a6c..895f934 100644
>> > --- a/drivers/gpu/drm/i915/intel_dp.c
>> > +++ b/drivers/gpu/drm/i915/intel_dp.c
>> > @@ -5924,6 +5924,29 @@ 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)
>> > @@ -5936,6 +5959,10 @@ 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 0048b52..955b239 100644
>> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
>> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
>> > @@ -313,6 +313,24 @@ 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);
>> 
>> This is where the new boolean intel_dp->train_set_valid will have to be set to false on failure.
>> This ensures that we dont end up retraining at the same parameters in intel_dp_check_link_status()
>> 
>> So in intel_dp_check-link_status , just before retraining it will add a check, 
>> if (!intel_dp->train_set_valid)
>> return;
>> 
>> Ville/Jani what are your thoughts on this?
>> 
>> Regards
>> Manasi
>> 
>> > +	return;
>> >  }
>> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>> > index 51228fe..0fe1ac8 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
>> > 
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Jani Nikula, Intel Open Source Technology Center
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