Re: [PATCH 1/4] drm/i915: Make atomic use in-flight state for CRTC active value

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Apr 09, 2015 at 07:00:31AM -0700, Matt Roper wrote:
> On Thu, Apr 09, 2015 at 02:42:36PM +0200, Daniel Vetter wrote:
> > On Wed, Apr 08, 2015 at 06:56:51PM -0700, Matt Roper wrote:
> > > Our atomic plane code currently uses intel_crtc->active to determine
> > > how/when to update some derived state values.  This works fine for pure
> > > plane updates at the moment since the CRTC state itself isn't changed as
> > > part of the operation.  However as we convert more of our driver
> > > internals over to atomic modesetting, we need to look at whether the
> > > CRTC will be active at the *end* of the atomic transaction (which may
> > > not match the currently committed state).
> > > 
> > > The in-flight value we want to use is generally in a crtc_state object
> > > associated with our top-level atomic transaction.  However there are a
> > > few cases where this isn't the case:
> > > 
> > >  * While using transitional atomic helpers (as we are at the moment),
> > >    SetPlane() calls will operate on orphaned plane states that aren't
> > >    part of a top-level atomic transaction.  In this case, we're not
> > >    touching the CRTC state, so it's fine to use the already-committed
> > >    value from crtc->state.
> > > 
> > >  * While updating properties of a disabled plane, we'll have a top-level
> > >    atomic state, but it may not contain the CRTC state we're looking
> > >    for.  Once again, this means we're not actually touching any CRTC
> > >    state so it's safe to use the value from crtc->state directly.
> > > 
> > > Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_atomic_plane.c | 11 +++--
> > >  drivers/gpu/drm/i915/intel_display.c      | 73 +++++++++++++++++++++++++++++--
> > >  drivers/gpu/drm/i915/intel_drv.h          |  3 ++
> > >  drivers/gpu/drm/i915/intel_sprite.c       | 16 +++++--
> > >  4 files changed, 93 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_atomic_plane.c b/drivers/gpu/drm/i915/intel_atomic_plane.c
> > > index 976b891..90c4a82 100644
> > > --- a/drivers/gpu/drm/i915/intel_atomic_plane.c
> > > +++ b/drivers/gpu/drm/i915/intel_atomic_plane.c
> > > @@ -111,12 +111,17 @@ static int intel_plane_atomic_check(struct drm_plane *plane,
> > >  {
> > >  	struct drm_crtc *crtc = state->crtc;
> > >  	struct intel_crtc *intel_crtc;
> > > +	struct intel_crtc_state *intel_crtc_state;
> > >  	struct intel_plane *intel_plane = to_intel_plane(plane);
> > >  	struct intel_plane_state *intel_state = to_intel_plane_state(state);
> > > +	bool active;
> > >  
> > >  	crtc = crtc ? crtc : plane->crtc;
> > >  	intel_crtc = to_intel_crtc(crtc);
> > >  
> > > +	intel_crtc_state = intel_crtc_state_for_plane(intel_state);
> > > +	active = intel_crtc_state->base.enable;
> > > +
> > >  	/*
> > >  	 * Both crtc and plane->crtc could be NULL if we're updating a
> > >  	 * property while the plane is disabled.  We don't actually have
> > > @@ -143,10 +148,8 @@ static int intel_plane_atomic_check(struct drm_plane *plane,
> > >  	/* Clip all planes to CRTC size, or 0x0 if CRTC is disabled */
> > >  	intel_state->clip.x1 = 0;
> > >  	intel_state->clip.y1 = 0;
> > > -	intel_state->clip.x2 =
> > > -		intel_crtc->active ? intel_crtc->config->pipe_src_w : 0;
> > > -	intel_state->clip.y2 =
> > > -		intel_crtc->active ? intel_crtc->config->pipe_src_h : 0;
> > > +	intel_state->clip.x2 = active ? intel_crtc_state->pipe_src_w : 0;
> > > +	intel_state->clip.y2 = active ? intel_crtc_state->pipe_src_h : 0;
> > >  
> > >  	/*
> > >  	 * Disabling a plane is always okay; we just need to update
> > > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > > index 7bfe2af..88b0f69 100644
> > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > @@ -12562,6 +12562,53 @@ intel_cleanup_plane_fb(struct drm_plane *plane,
> > >  	}
> > >  }
> > >  
> > > +/**
> > > + * intel_crtc_state_for_plane - Obtain CRTC state for a plane
> > > + * @pstate: plane state to lookup corresponding crtc state for
> > > + *
> > > + * When working with a top-level atomic transaction (drm_atomic_state),
> > > + * a CRTC state should be present that corresponds to the provided
> > > + * plane state; this function provides a quick way to fetch that
> > > + * CRTC state.  In cases where we have a plane state unassociated with any
> > > + * top-level atomic transaction (e.g., while using the transitional atomic
> > > + * helpers), the current CRTC state from crtc->state will be returned
> > > + * instead.
> > > + */
> > > +struct intel_crtc_state *
> > > +intel_crtc_state_for_plane(struct intel_plane_state *pstate)
> > > +{
> > > +	struct drm_atomic_state *state = pstate->base.state;
> > > +	struct intel_plane *plane = to_intel_plane(pstate->base.plane);
> > > +	struct drm_crtc *crtc = intel_get_crtc_for_pipe(pstate->base.plane->dev,
> > > +							plane->pipe);
> > > +	int i;
> > > +
> > > +	/*
> > > +	 * While using transitional plane helpers, we may not have a top-level
> > > +	 * atomic transaction.  Of course that also means that we're not
> > > +	 * actually touching CRTC state, so just return the currently
> > > +	 * committed state.
> > > +	 */
> > 
> > Imo this needs a big FIXME at the top of the comment ;-)
> > 
> > > +	if (!state)
> > > +		return to_intel_crtc_state(crtc->state);
> > > +
> > > +	for (i = 0; i < state->dev->mode_config.num_crtc; i++) {
> > > +		if (!state->crtcs[i])
> > > +			continue;
> > > +
> > > +		if (to_intel_crtc(state->crtcs[i])->pipe == plane->pipe)
> > > +			return to_intel_crtc_state(state->crtc_states[i]);
> > > +	}
> > > +
> > > +	/*
> > > +	 * We may have a plane state without a corresponding CRTC state if
> > > +	 * we're updating a property of a disabled plane.  Again, just using
> > > +	 * the already-committed state for this plane's CRTC should be fine
> > > +	 * since we're not actually touching the CRTC here.
> > > +	 */
> > 
> > Is this really still true with Ander's patches? If the udpate is part of a
> > drm_atomic_state structure, then we should always have the corresponding
> > crtc state handy I think. Which cases still fail this assumption?
> 
> Any time a transaction updates a plane, the corresponding CRTC state (as
> defined by plane_state->crtc) should get added to the transaction by the
> atomic core code (specifically in drm_atomic_get_plane_state).  But when
> a plane is disabled, state->crtc is NULL so there simply is no
> associated CRTC to add (at least as far as the core is concerned).  So
> you wind up with just a plane state being added to the top-level atomic
> state in that case.

We add both the old and the new crtc state, so when you disable a plane
you should have the crtc state at hand. Except when a plane is already
disable, but I guess in that case we should just not call any of the
callbacks?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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