Re: [Intel-gfx] [PATCH v5 1/3] drm/i915/dp: Make sure all tiled connectors get added to the state with full modeset

[Manasi Navare <manasi.d.navare@intel.com>]

On Fri, Dec 27, 2019 at 10:36:52AM -0800, Matt Roper wrote:
> On Mon, Dec 23, 2019 at 02:44:27PM -0800, Manasi Navare wrote:
> > In case of tiled displays, all the tiles are linke dto each other
> > for transcoder port sync. So in intel_atomic_check() we need to make
> > sure that we add all the tiles to the modeset and if one of the
> > tiles needs a full modeset then mark all other tiles for a full modeset.
> > 
> > We also need to force modeset for all synced crtcs after fastset check.
> > 
> > v5:
> > * Rebase
> 
> I sent a reply to your v4 of this right at the same time you sent out
> v5, but I'm not sure if my reply went through since it doesn't show up
> in patchwork.  I've included the same feedback I gave on v4 below in
> case it got lost, plus a few more comments.
> 
> > v4:
> > * Fix logic for modeset_synced_crtcs (Ville)
> > v3:
> > * Add tile checks only for Gen >11
> > v2:
> > * Change crtc_state scope, remove tile_grp_id (Ville)
> > * Use intel_connector_needs_modeset() (Ville)
> > * Add modeset_synced_crtcs (Ville)
> > * Make sure synced crtcs are forced full modeset
> > after fastset check (Ville)
> > 
> > Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: José Roberto de Souza <jose.souza@intel.com>
> > Cc: Matt Roper <matthew.d.roper@intel.com>
> > Bugzilla: https://gitlab.freedesktop.org/drm/intel/issues/5
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_display.c | 123 +++++++++++++++++++
> >  1 file changed, 123 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> > index 94fc4b5bacc0..45a699bac34a 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > @@ -14304,6 +14304,118 @@ static bool intel_cpu_transcoder_needs_modeset(struct intel_atomic_state *state,
> >  	return false;
> >  }
> >  
> > +static void
> > +intel_modeset_synced_crtcs(struct intel_atomic_state *state,
> > +			   u8 transcoders)
> > +{
> > +	struct intel_crtc_state *new_crtc_state;
> > +	struct intel_crtc *crtc;
> > +	int i;
> > +
> > +	for_each_new_intel_crtc_in_state(state, crtc,
> > +					 new_crtc_state, i) {
> 
> Are we guaranteed to have the other CRTC in the state at this point?  If
> the tile information was gone at the beginning of the transaction, then
> it wouldn't have known to bring in the other CRTC.  So if a modeset was
> only submitted on one of the two synchronized CRTCs then I don't see
> where the other one would be added to the transaction before this point?
>

Yes basically at this point the new crtc state is not cleared so we use the 
previously synced crtcs through new crtc state master slave assignments from previous
modeset.

 
> > +		if (transcoders & BIT(new_crtc_state->cpu_transcoder)) {
> > +			new_crtc_state->uapi.mode_changed = true;
> > +			new_crtc_state->update_pipe = false;
> > +		}
> > +	}
> > +}
> > +
> > +static void
> > +intel_atomic_check_synced_crtcs(struct intel_atomic_state *state)
> > +{
> > +	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> > +	struct intel_crtc_state *new_crtc_state;
> > +	struct intel_crtc *crtc;
> > +	int i;
> > +
> > +	if (INTEL_GEN(dev_priv) < 11)
> > +		return;
> > +
> > +	for_each_new_intel_crtc_in_state(state, crtc,
> > +					 new_crtc_state, i) {
> > +		if (is_trans_port_sync_master(new_crtc_state) &&
> > +		    needs_modeset(new_crtc_state)) {
> > +			intel_modeset_synced_crtcs(state,
> > +						   new_crtc_state->sync_mode_slaves_mask);
> > +		} else if (is_trans_port_sync_slave(new_crtc_state) &&
> > +			   needs_modeset(new_crtc_state)) {
> > +			intel_modeset_synced_crtcs(state,
> > +						   BIT(new_crtc_state->master_transcoder));
> > +		}
> > +	}
> > +}
> > +
> > +static int
> > +intel_modeset_all_tiles(struct intel_atomic_state *state, int tile_grp_id)
> > +{
> > +	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> > +	struct drm_connector *connector;
> > +	struct drm_connector_list_iter conn_iter;
> > +	int ret = 0;
> > +
> > +	drm_connector_list_iter_begin(&dev_priv->drm, &conn_iter);
> > +	drm_for_each_connector_iter(connector, &conn_iter) {
> > +		struct drm_connector_state *conn_state;
> > +		struct drm_crtc_state *crtc_state;
> > +
> > +		if (!connector->has_tile ||
> > +		    connector->tile_group->id != tile_grp_id)
> > +			continue;
> > +		conn_state = drm_atomic_get_connector_state(&state->base,
> > +							    connector);
> > +		if (IS_ERR(conn_state)) {
> > +			ret =  PTR_ERR(conn_state);
> > +			break;
> > +		}
> > +
> > +		if (!conn_state->crtc)
> > +			continue;
> > +
> > +		crtc_state = drm_atomic_get_crtc_state(&state->base,
> > +						       conn_state->crtc);
> > +		if (IS_ERR(crtc_state)) {
> > +			ret = PTR_ERR(conn_state);
> > +			break;
> > +		}
> > +		crtc_state->mode_changed = true;
> > +		ret = drm_atomic_add_affected_connectors(&state->base,
> > +							 conn_state->crtc);
> > +		if (ret)
> > +			break;
> > +	}
> > +	drm_connector_list_iter_end(&conn_iter);
> > +
> > +	return ret;
> > +}
> 
> There isn't really anything i915-specific in this function and it feels
> like something other drivers may need as well if they treat tiled
> monitors in a similar manner.  We may want to consider pulling this out
> to a DRM core helper, although we can do that in a future patch.
> 
> With a bit of extra work, the function below could also potentially be
> moved to the core too.  Do you know if there's other hardware with port
> sync capabilities that could benefit from these?
>

Yes definitely can eventually make this a drm helper even though the whole master slave
thing is i915 specific for now
 
> > +
> > +static int
> > +intel_atomic_check_tiled_conns(struct intel_atomic_state *state)
> > +{
> > +	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
> > +	struct drm_connector *connector;
> > +	struct drm_connector_state *old_conn_state, *new_conn_state;
> > +	int i, ret;
> > +
> > +	if (INTEL_GEN(dev_priv) < 11)
> > +		return 0;
> > +
> > +	/* Is tiled, mark all other tiled CRTCs as needing a modeset */
> > +	for_each_oldnew_connector_in_state(&state->base, connector,
> > +					   old_conn_state, new_conn_state, i) {
> > +		if (!connector->has_tile)
> > +			continue;
> > +		if (!intel_connector_needs_modeset(state, connector))
> > +			continue;
> > +
> > +		ret = intel_modeset_all_tiles(state, connector->tile_group->id);
> > +		if (ret)
> > +			return ret;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >  /**
> >   * intel_atomic_check - validate state object
> >   * @dev: drm device
> > @@ -14331,6 +14443,10 @@ static int intel_atomic_check(struct drm_device *dev,
> >  	if (ret)
> >  		goto fail;
> >  
> > +	ret = intel_atomic_check_tiled_conns(state);
> > +	if (ret)
> > +		goto fail;
> > +
> >  	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state,
> >  					    new_crtc_state, i) {
> >  		if (!needs_modeset(new_crtc_state)) {
> > @@ -14378,6 +14494,13 @@ static int intel_atomic_check(struct drm_device *dev,
> >  		}
> >  	}
> >  
> > +	/*
> > +	 * In case of port synced crtcs, if one of the synced crtcs
> > +	 * needs a full modeset, all other synced crtcs should be
> > +	 * forced a full modeset.
> 
> Since it's somewhat non-intuitive, I'd add a little bit of extra
> explanation for why intel_atomic_check_tiled_conns above didn't already
> take care of this.  I.e., if you've plugged in a different monitor, the
> tile information may have already vanished from drm_connector by the
> time we start this atomic transaction, so we still need to deal with
> connectors that used to be tiled (and thus were port-synced) but no
> longer are.
>

Yes will add this in the comments
 
> 
> > +	 */
> > +	intel_atomic_check_synced_crtcs(state);
> 
> Although I can't think of a reason why it would cause a problem in this
> case, we do seem to be violating the directions in the big kerneldoc
> warning attached to drm_atomic_helper_check_modeset().  I.e. if we set
> mode_changed in our own check functions, then we're supposed to re-call
> drm_atomic_helper_check_modeset() to make sure everything is properly
> handled.  If we're not going to follow those directions, we should
> probably be clear why we don't think it's necessary.
> 
> Actually, I wonder if some of this tiling handling should eventually
> migrate into that core helper function in the future...
>

We are setting the mode hanged to true directly in our function so yes it makes
sense to eventually do that as part of the core helper function but i still
dont see the need for us to call drm_atomic_helper_check_modeset() again
since our function is essentially checking modeset based on the tiled conditions

Manasi
 
> 
> Matt
> 
> > +
> >  	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state,
> >  					    new_crtc_state, i) {
> >  		if (needs_modeset(new_crtc_state)) {
> > -- 
> > 2.19.1
> > 
> 
> -- 
> Matt Roper
> Graphics Software Engineer
> VTT-OSGC Platform Enablement
> Intel Corporation
> (916) 356-2795
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