Re: [Intel-gfx] [PATCH 2/2] drm/i915: Push MST link retraining to the hotplug work

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Apr 17, 2020 at 02:50:39PM -0400, Lyude Paul wrote:
> On Fri, 2020-04-17 at 18:27 +0300, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > We shouldn't try to do link retraining from the short hpd handler.
> > We can't take any modeset locks there so this is racy as hell.
> > Push the whole thing into the hotplug work like we do with SST.
> > 
> > We'll just have to adjust the SST retraining code to deal with
> > the MST encoders and multiple pipes.
> > 
> > TODO: I have a feeling we should just rip this all out and
> > do a full modeset instead. Stuff like port sync and the tgl+
> > MST master transcoder stuff maybe doesn't work well if we
> > try to retrain without following the proper modeset sequence.
> > So far haven't done any actual tests to confirm that though.
> 
> To answer your feeling here: yes-we should, I have some branches for doing
> this sort of thing with i915 but they are ancient at this point. Once I get to
> fallback link retraining we should be able to use this in i915 to handle
> figuring out what all needs to be reset for an MST training.

Not sure what else we'd have to do but set connectors_changed=true on
all the relevant connectors and commit.

> 
> fwiw - If you have some need for fallback link retraining soon I can move it
> up on my todo list for MST. I've got the hard design parts already figured out
> from the last time I tried implementing it, so writing new patches shouldn't
> be too difficult.
> 
> (note - this patch is still worth merging I'd imagine, since this looks like
> it should at least handle retraining an MST topology at the same link rate
> just fine)
> 
> > 
> > Cc: Lyude Paul <lyude@redhat.com>
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp.c | 165 ++++++++++++++++++------
> >  1 file changed, 122 insertions(+), 43 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 4d4898db38e9..556371338aa9 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -5628,6 +5628,7 @@ static int
> >  intel_dp_check_mst_status(struct intel_dp *intel_dp)
> >  {
> >  	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > +	bool need_retrain = false;
> >  
> >  	if (!intel_dp->is_mst)
> >  		return -EINVAL;
> > @@ -5647,16 +5648,11 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
> >  		}
> >  
> >  		/* check link status - esi[10] = 0x200c */
> > -		/*
> > -		 * FIXME kill this and use the SST retraining approach
> > -		 * for MST as well.
> > -		 */
> > -		if (intel_dp->active_mst_links > 0 &&
> > +		if (intel_dp->active_mst_links > 0 && !need_retrain &&
> >  		    !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
> >  			drm_dbg_kms(&i915->drm,
> >  				    "channel EQ not ok, retraining\n");
> > -			intel_dp_start_link_train(intel_dp);
> > -			intel_dp_stop_link_train(intel_dp);
> > +			need_retrain = true;
> >  		}
> >  
> >  		drm_dbg_kms(&i915->drm, "got esi %3ph\n", esi);
> > @@ -5676,7 +5672,7 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
> >  		}
> >  	}
> >  
> > -	return 0;
> > +	return need_retrain;
> >  }
> >  
> >  static bool
> > @@ -5713,20 +5709,102 @@ intel_dp_needs_link_retrain(struct intel_dp
> > *intel_dp)
> >  	return !drm_dp_channel_eq_ok(link_status, intel_dp->lane_count);
> >  }
> >  
> > +static bool intel_dp_has_connector(struct intel_dp *intel_dp,
> > +				   const struct drm_connector_state
> > *conn_state)
> > +{
> > +	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > +	struct intel_encoder *encoder;
> > +	enum pipe pipe;
> > +
> > +	if (!conn_state->best_encoder)
> > +		return false;
> > +
> > +	/* SST */
> > +	encoder = &dp_to_dig_port(intel_dp)->base;
> > +	if (conn_state->best_encoder == &encoder->base)
> > +		return true;
> > +
> > +	/* MST */
> > +	for_each_pipe(i915, pipe) {
> > +		encoder = &intel_dp->mst_encoders[pipe]->base;
> > +		if (conn_state->best_encoder == &encoder->base)
> > +			return true;
> > +	}
> > +
> > +	return false;
> > +}
> > +
> > +static int intel_dp_prep_link_retrain(struct intel_dp *intel_dp,
> > +				      struct drm_modeset_acquire_ctx *ctx,
> > +				      u32 *crtc_mask)
> > +{
> > +	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > +	struct drm_connector_list_iter conn_iter;
> > +	struct intel_connector *connector;
> > +	int ret = 0;
> > +
> > +	*crtc_mask = 0;
> > +
> > +	if (!intel_dp_needs_link_retrain(intel_dp))
> > +		return 0;
> > +
> > +	drm_connector_list_iter_begin(&i915->drm, &conn_iter);
> > +	for_each_intel_connector_iter(connector, &conn_iter) {
> > +		struct drm_connector_state *conn_state =
> > +			connector->base.state;
> > +		struct intel_crtc_state *crtc_state;
> > +		struct intel_crtc *crtc;
> > +
> > +		if (!intel_dp_has_connector(intel_dp, conn_state))
> > +			continue;
> > +
> > +		crtc = to_intel_crtc(conn_state->crtc);
> > +		if (!crtc)
> > +			continue;
> > +
> > +		ret = drm_modeset_lock(&crtc->base.mutex, ctx);
> > +		if (ret)
> > +			break;
> > +
> > +		crtc_state = to_intel_crtc_state(crtc->base.state);
> > +
> > +		drm_WARN_ON(&i915->drm,
> > !intel_crtc_has_dp_encoder(crtc_state));
> > +
> > +		if (!crtc_state->hw.active)
> > +			continue;
> > +
> > +		if (conn_state->commit &&
> > +		    !try_wait_for_completion(&conn_state->commit->hw_done))
> > +			continue;
> > +
> > +		*crtc_mask |= drm_crtc_mask(&crtc->base);
> > +	}
> > +	drm_connector_list_iter_end(&conn_iter);
> > +
> > +	if (!intel_dp_needs_link_retrain(intel_dp))
> > +		*crtc_mask = 0;
> 
> Also fwiw ^ this is the kind of logic I was thinking for the MST helpers (e.g.
> having helpers (+ setting link_status for each affected connector, etc. et.).
> again though-it's fine if this stays in i915 for now, but we should move it in
> the future.
> 
> > +
> > +	return ret;
> > +}
> > +
> > +static bool intel_dp_is_connected(struct intel_dp *intel_dp)
> > +{
> > +	struct intel_connector *connector = intel_dp->attached_connector;
> > +
> > +	return connector->base.status == connector_status_connected ||
> > +		intel_dp->is_mst;
> > +}
> > +
> >  int intel_dp_retrain_link(struct intel_encoder *encoder,
> >  			  struct drm_modeset_acquire_ctx *ctx)
> >  {
> >  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> >  	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> > -	struct intel_connector *connector = intel_dp->attached_connector;
> > -	struct drm_connector_state *conn_state;
> > -	struct intel_crtc_state *crtc_state;
> >  	struct intel_crtc *crtc;
> > +	u32 crtc_mask;
> >  	int ret;
> >  
> > -	/* FIXME handle the MST connectors as well */
> > -
> > -	if (!connector || connector->base.status !=
> > connector_status_connected)
> > +	if (!intel_dp_is_connected(intel_dp))
> >  		return 0;
> >  
> >  	ret = drm_modeset_lock(&dev_priv->drm.mode_config.connection_mutex,
> > @@ -5734,46 +5812,42 @@ int intel_dp_retrain_link(struct intel_encoder
> > *encoder,
> >  	if (ret)
> >  		return ret;
> >  
> > -	conn_state = connector->base.state;
> > -
> > -	crtc = to_intel_crtc(conn_state->crtc);
> > -	if (!crtc)
> > -		return 0;
> > -
> > -	ret = drm_modeset_lock(&crtc->base.mutex, ctx);
> > +	ret = intel_dp_prep_link_retrain(intel_dp, ctx, &crtc_mask);
> >  	if (ret)
> >  		return ret;
> >  
> > -	crtc_state = to_intel_crtc_state(crtc->base.state);
> > -
> > -	drm_WARN_ON(&dev_priv->drm, !intel_crtc_has_dp_encoder(crtc_state));
> > -
> > -	if (!crtc_state->hw.active)
> > +	if (crtc_mask == 0)
> >  		return 0;
> >  
> > -	if (conn_state->commit &&
> > -	    !try_wait_for_completion(&conn_state->commit->hw_done))
> > -		return 0;
> > +	drm_dbg_kms(&dev_priv->drm, "[ENCODER:%d:%s] retraining link\n",
> > +		    encoder->base.base.id, encoder->base.name);
> >  
> > -	if (!intel_dp_needs_link_retrain(intel_dp))
> > -		return 0;
> > +	for_each_intel_crtc_mask(&dev_priv->drm, crtc, crtc_mask) {
> > +		const struct intel_crtc_state *crtc_state =
> > +			to_intel_crtc_state(crtc->base.state);
> >  
> > -	/* Suppress underruns caused by re-training */
> > -	intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe, false);
> > -	if (crtc_state->has_pch_encoder)
> > -		intel_set_pch_fifo_underrun_reporting(dev_priv,
> > -						      intel_crtc_pch_transcode
> > r(crtc), false);
> > +		/* Suppress underruns caused by re-training */
> > +		intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe,
> > false);
> > +		if (crtc_state->has_pch_encoder)
> > +			intel_set_pch_fifo_underrun_reporting(dev_priv,
> > +							      intel_crtc_pch_t
> > ranscoder(crtc), false);
> > +	}
> >  
> >  	intel_dp_start_link_train(intel_dp);
> >  	intel_dp_stop_link_train(intel_dp);
> >  
> > -	/* Keep underrun reporting disabled until things are stable */
> > -	intel_wait_for_vblank(dev_priv, crtc->pipe);
> > +	for_each_intel_crtc_mask(&dev_priv->drm, crtc, crtc_mask) {
> > +		const struct intel_crtc_state *crtc_state =
> > +			to_intel_crtc_state(crtc->base.state);
> >  
> > -	intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe, true);
> > -	if (crtc_state->has_pch_encoder)
> > -		intel_set_pch_fifo_underrun_reporting(dev_priv,
> > -						      intel_crtc_pch_transcode
> > r(crtc), true);
> > +		/* Keep underrun reporting disabled until things are stable */
> > +		intel_wait_for_vblank(dev_priv, crtc->pipe);
> > +
> > +		intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe,
> > true);
> > +		if (crtc_state->has_pch_encoder)
> > +			intel_set_pch_fifo_underrun_reporting(dev_priv,
> > +							      intel_crtc_pch_t
> > ranscoder(crtc), true);
> > +	}
> >  
> >  	return 0;
> >  }
> > @@ -7415,7 +7489,8 @@ intel_dp_hpd_pulse(struct intel_digital_port
> > *intel_dig_port, bool long_hpd)
> >  	}
> >  
> >  	if (intel_dp->is_mst) {
> > -		if (intel_dp_check_mst_status(intel_dp) == -EINVAL) {
> > +		switch (intel_dp_check_mst_status(intel_dp)) {
> > +		case -EINVAL:
> >  			/*
> >  			 * If we were in MST mode, and device is not
> >  			 * there, get out of MST mode
> > @@ -7429,6 +7504,10 @@ intel_dp_hpd_pulse(struct intel_digital_port
> > *intel_dig_port, bool long_hpd)
> >  							intel_dp->is_mst);
> >  
> >  			return IRQ_NONE;
> > +		case 1:
> > +			return IRQ_NONE;
> > +		default:
> > +			break;
> >  		}
> >  	}
> >  
> -- 
> Cheers,
> 	Lyude Paul (she/her)
> 	Associate Software Engineer at Red Hat

-- 
Ville Syrjälä
Intel
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