Re: [Intel-gfx] [PATCH v4 5/6] drm/i915/display: Check if pipe fastset is allowed by external dependencies

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

On Wed, Dec 18, 2019 at 08:19:15PM +0000, Souza, Jose wrote:
> On Wed, 2019-12-18 at 21:39 +0200, Ville Syrjälä wrote:
> > On Wed, Dec 18, 2019 at 10:59:09AM -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
> > > 
> > > v4:
> > > - added a function to return if MST master neeeds modeset to simply
> > > code in intel_atomic_check()
> > > 
> > > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/display/intel_display.c | 53 +++++++++++++++-
> > > ----
> > >  drivers/gpu/drm/i915/display/intel_dp_mst.c  | 14 ++++++
> > >  drivers/gpu/drm/i915/display/intel_dp_mst.h  |  3 ++
> > >  3 files changed, 57 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> > > b/drivers/gpu/drm/i915/display/intel_display.c
> > > index a4f252d05b37..2a406891567b 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > > @@ -13903,19 +13903,6 @@ 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,
> > > @@ -14083,6 +14070,46 @@ 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) {
> > > +		enum transcoder master = new_crtc_state-
> > > >mst_master_transcoder;
> > > +
> > > +		if (!intel_dp_mst_is_slave_trans(new_crtc_state) ||
> > > +		    needs_modeset(new_crtc_state))
> > > +			continue;
> > > +
> > > +		if (intel_dp_mst_master_trans_needs_modeset(state,
> > > master)) {
> > 
> > I think this has the loops the opposite way of what I was thinking,
> > but should work fine I think... OK. I'm convinced your way is in fact
> > better.
> > 
> > > +			new_crtc_state->uapi.mode_changed = true;
> > > +			new_crtc_state->update_pipe = false;
> > > +		}
> > > +	}
> > > +
> > > +	for_each_oldnew_intel_crtc_in_state(state, crtc,
> > > old_crtc_state,
> > > +					    new_crtc_state, i) {
> > > +		if (needs_modeset(new_crtc_state))
> > > +			continue;
> > 
> > I suppose there isn't any way we should have crtcs in the state that
> > neither have update_pipe or needs_modeset flagged here. Could maybe
> > WARN_ON(!update_pipe) here if we're being paranoid.
> 
> Adding the WARN_ON
> 
> > 
> > > +
> > > +		/*
> > > +		 * 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;
> > 
> > Still a bit unhappy having this state copy inlined in
> > intel_atomic_check().
> > 
> > > +	}
> > > +
> > >  	if (any_ms && !check_digital_port_conflicts(state)) {
> > >  		DRM_DEBUG_KMS("rejecting conflicting digital port
> > > configuration\n");
> > >  		ret = EINVAL;
> > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > index efd14b0b507b..4aba1d702a83 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > @@ -854,3 +854,17 @@ bool intel_dp_mst_is_slave_trans(const struct
> > > intel_crtc_state *crtc_state)
> > >  	return crtc_state->mst_master_transcoder != INVALID_TRANSCODER
> > > &&
> > >  	       crtc_state->mst_master_transcoder != crtc_state-
> > > >cpu_transcoder;
> > >  }
> > > +
> > > +bool intel_dp_mst_master_trans_needs_modeset(struct
> > > intel_atomic_state *state,
> > > +					     enum transcoder master)
> > 
> > Are we going to need this elsewhere? Or be static in intel_display.c?
> > Not that people are 100% happy of stuffing everything in there.
> 
> Not needed elsewhere, I'm also trying to not put more stuff in
> intel_display.c.
> 
> > 
> > > +{
> > > +	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)
> > > +		if (new_crtc_state->mst_master_transcoder == master)
> > 
> > So we need to modeset everything when either the master or any
> > other slave wants to modeset? That is, we can't just modeset slaves
> > independently and only force the modesets for all slaves if the
> > master
> > needs a modeset?
> 
> If a slave needs a modeset we don't need to do a modeset in master or
> in other slaves.
> 
> This is doing independent modeset in slaves and forcing modeset to all
> slaves when master needs as modeset.

If you just wanted to check if the master needs a modeset then shouldn't
it just compare crtc_state->cpu_transcoder == master?

And in that case it's not at all MST specific and we could just call it
intel_cpu_transcoder_needs_modeset() or something.

> 
> > 
> > > +			return
> > > drm_atomic_crtc_needs_modeset(&new_crtc_state->uapi);
> > > +
> > > +	return false;
> > > +}
> > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.h
> > > b/drivers/gpu/drm/i915/display/intel_dp_mst.h
> > > index 854724f68f09..72cb486f32ab 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.h
> > > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.h
> > > @@ -8,6 +8,7 @@
> > >  
> > >  #include <linux/types.h>
> > >  
> > > +struct intel_atomic_state;
> > >  struct intel_digital_port;
> > >  struct intel_crtc_state;
> > >  
> > > @@ -16,5 +17,7 @@ void intel_dp_mst_encoder_cleanup(struct
> > > intel_digital_port *intel_dig_port);
> > >  int intel_dp_mst_encoder_active_links(struct intel_digital_port
> > > *intel_dig_port);
> > >  bool intel_dp_mst_is_master_trans(const struct intel_crtc_state
> > > *crtc_state);
> > >  bool intel_dp_mst_is_slave_trans(const struct intel_crtc_state
> > > *crtc_state);
> > > +bool intel_dp_mst_master_trans_needs_modeset(struct
> > > intel_atomic_state *state,
> > > +					     enum transcoder master);
> > >  
> > >  #endif /* __INTEL_DP_MST_H__ */
> > > -- 
> > > 2.24.1

-- 
Ville Syrjälä
Intel
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