[Intel-gfx] [PATCH v3 10/11] drm/i915/display: Check if pipe fastset is allowed by external dependencies

[Souza, Jose]

On Wed, 2019-12-18 at 19:10 +0200, Ville Syrjälä wrote:
> On Wed, Dec 18, 2019 at 07:00:19PM +0200, Ville Syrjälä wrote:
> > On Mon, Dec 16, 2019 at 02:07:41PM -0800, José Roberto de Souza
> > wrote:
> > > Check if fastset is allowed by external dependencies like other
> > > pipes
> > > and transcoders.
> > > 
> > > Right now this patch only forces a fullmodeset in MST slaves of
> > > MST
> > > masters that needs a fullmodeset but it will be needed for port
> > > sync
> > > as well.
> > > 
> > > v3:
> > > - moved handling to intel_atomic_check() this way is guarantee
> > > that
> > > all pipes will have its state computed
> > > 
> > > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > Cc: Lucas De Marchi <lucas.demarchi at intel.com>
> > > Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> > > Cc: Manasi Navare <manasi.d.navare at intel.com>
> > > Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/display/intel_display.c | 63
> > > ++++++++++++++++----
> > >  1 file changed, 50 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> > > b/drivers/gpu/drm/i915/display/intel_display.c
> > > index f1c0687bf69b..2627a7bcb45c 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > > @@ -13941,19 +13941,6 @@ static void
> > > intel_crtc_check_fastset(const struct intel_crtc_state
> > > *old_crtc_sta
> > >  
> > >  	new_crtc_state->uapi.mode_changed = false;
> > >  	new_crtc_state->update_pipe = true;
> > > -
> > > -	/*
> > > -	 * If we're not doing the full modeset we want to
> > > -	 * keep the current M/N values as they may be
> > > -	 * sufficiently different to the computed values
> > > -	 * to cause problems.
> > > -	 *
> > > -	 * FIXME: should really copy more fuzzy state here
> > > -	 */
> > > -	new_crtc_state->fdi_m_n = old_crtc_state->fdi_m_n;
> > > -	new_crtc_state->dp_m_n = old_crtc_state->dp_m_n;
> > > -	new_crtc_state->dp_m2_n2 = old_crtc_state->dp_m2_n2;
> > > -	new_crtc_state->has_drrs = old_crtc_state->has_drrs;
> > >  }
> > >  
> > >  static int intel_crtc_add_planes_to_state(struct
> > > intel_atomic_state *state,
> > > @@ -14121,6 +14108,56 @@ static int intel_atomic_check(struct
> > > drm_device *dev,
> > >  			any_ms = true;
> > >  	}
> > >  
> > > +	/**
> > > +	 * Check if fastset is allowed by external dependencies like
> > > other
> > > +	 * pipes and transcoders.
> > > +	 *
> > > +	 * Right now it only forces a fullmodeset when the MST master
> > > +	 * transcoder did not changed but the pipe of the master
> > > transcoder
> > > +	 * needs a fullmodeset so all slaves also needs to do a
> > > fullmodeset.
> > > +	 */
> > > +	for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state,
> > > i) {
> > > +		struct intel_crtc_state *new_crtc_state_iter;
> > > +		struct intel_crtc *crtc_iter;
> > > +		int j;
> > > +
> > > +		if (!intel_dp_mst_is_slave_trans(new_crtc_state) ||
> > > +		    needs_modeset(new_crtc_state))
> > 
> > shouldn't this be
> > if (!mst_master || !needs_modeset)
> > 	continue;

When iterating over MST pipes in older gens
intel_dp_mst_is_master_trans() and intel_dp_mst_is_slave_trans() will
always return false and if this one is intel_dp_mst_is_master_trans()
we can skip it.
In case it is a intel_dp_mst_is_slave_trans() and if it needs a modeset
already we don't need to force anything.


> > ?
> > 
> > > +			continue;
> > > +
> > > +		for_each_new_intel_crtc_in_state(state, crtc_iter,
> > > +						 new_crtc_state_iter,
> > > j) {
> > > +			if (new_crtc_state->mst_master_transcoder !=
> > > +			    new_crtc_state_iter->cpu_transcoder)
> > > +				continue;
> > > +
> > > +			if (needs_modeset(new_crtc_state_iter)) {
> > > +				new_crtc_state->uapi.mode_changed =
> > > true;
> > > +				new_crtc_state->update_pipe = false;
> > > +			}
> > > +			break;
> > 
> > Hmm. So I guess the break here is because we're going to keep
> > iterating
> > the outer loop anyway? Don't think that works with the
> > s/slave/master/
> > fix above.

This inner loop is to find the master of the pipe being check, when we
find it we can break and process the next pipe.

> > 
> > I suggest moving this inner loop into a separate function entirely.
> > Could simply pass in the master_transcoder to that function and
> > then
> > we wouldn't even have this clash with variable names for the two
> > crtcs/crtc_states.
> > 
> > Somethig like (with better funciton names ofc :)
> > 
> > mst_modeset_slaves(state, master_transcoder)
> > {
> > 	for_each() {
> > 		if (master_transcoder == crtc_state->master_transcoder)
> > 			modeset=1;
> > 	}
> > }

Sounds good the function above.

> > 
> > atomic_check()
> > {
> > 	for_each()
> > 		compute();
> > 
> > 	for_each() {
> > 		if (master && needs_modeset()
> > 			mst_modeset_slaves(state, crtc_state-
> > >cpu_transcoder);
> > 	}
> > 
> > 	for_each() {
> > 		if (fastset)
> > 			copy();
> > 	}
> > }
> > 
> > Or do we also need to force a modeset for the master if a slave
> > needs a
> > modeset? I'm trying to think if there's a way that we could end up
> > with
> > a slave changing its master (thus needing modeset) without the
> > master
> > being flagged for modeset...
> 
> How about this:
> 
> 1. Enable pipe B (master) + pipe C (slave)
> 2. Enable pipe A (should become master)
> 
> Hmm. Scratch that. Pipe B will have it's master_transcoder change
> from
> INVALID to A so it'll get flagged for a modeset. Seems I need a more
> heavy duty thinking cap for this one...
>