Re: [PATCH RESEND] drm: i915: Preserve old FBC status for update without new planes

[Paulo Zanoni <paulo.r.zanoni@intel.com>]

Em Qui, 2017-06-01 às 16:09 -0700, Manasi Navare escreveu:
> The modified commit message looks good to me.
> 
> Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>

As a longer term plan we could try to think some way to reduce the
complexity between the Kernel and IGT interaction here: maybe there's a
way to make things work without having to preserve no_fbc_reason
between multiple commits. But I don't have any specific ideas, so
suggestions are welcome.


> 
> On Thu, Jun 01, 2017 at 12:36:08PM -0300, Gabriel Krisman Bertazi
> wrote:
> > If the atomic commit doesn't include any new plane, there is no
> > need to
> > choose a new CRTC for FBC, and the intel_fbc_choose_crtc() will
> > bail out
> > early.  Although, if the FBC setup failed in the previous commit,
> > if the
> > current commit doesn't include new plane update, it tries to
> > overwrite
> > no_fbc_reason to "no suitable CRTC for FBC".  For that scenario, it
> > is
> > better that we simply keep the old message in-place to make
> > debugging
> > easier.
> > 
> > A scenario where this happens is with the
> > igt@kms_frontbuffer_tracking@fbc-suspend testcase when executed on
> > a
> > Haswell system with not enough stolen memory.  When enabling the
> > CRTC,
> > the FBC setup will be correctly initialized to a specific CRTC, but
> > won't be enabled, since there is not enough memory.  The testcase
> > will
> > then enable CRC checking, which requires a quirk for Haswell, which
> > issues a new atomic commit that doesn't update the planes.  Since
> > that
> > update doesn't include any new planes (and the FBC wasn't enabled),
> > intel_fbc_choose_crtc() will not find any suitable CRTC, but update
> > the
> > error message, hiding the lack of memory information, which is the
> > actual cause of the initialization failure.  As a result, this
> > causes
> > that test, which should skip, to fail on Haswell.
> > 
> > Changes since v1:
> >   - Update commit message (Manasi)
> > 
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100020
> > Fixes: f7e9b004b8a3 ("drm/i915/fbc: inline intel_fbc_can_choose()")
> > Reported-by: Dorota Czaplejewicz <dorota.czaplejewicz@collabora.co.
> > uk>
> > Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
> > Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_fbc.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_fbc.c
> > b/drivers/gpu/drm/i915/intel_fbc.c
> > index ded2add18b26..0c99c9b731ee 100644
> > --- a/drivers/gpu/drm/i915/intel_fbc.c
> > +++ b/drivers/gpu/drm/i915/intel_fbc.c
> > @@ -1045,6 +1045,7 @@ void intel_fbc_choose_crtc(struct
> > drm_i915_private *dev_priv,
> >  	struct drm_plane *plane;
> >  	struct drm_plane_state *plane_state;
> >  	bool crtc_chosen = false;
> > +	bool new_planes = false;
> >  	int i;
> >  
> >  	mutex_lock(&fbc->lock);
> > @@ -1066,6 +1067,7 @@ void intel_fbc_choose_crtc(struct
> > drm_i915_private *dev_priv,
> >  			to_intel_plane_state(plane_state);
> >  		struct intel_crtc_state *intel_crtc_state;
> >  		struct intel_crtc *crtc =
> > to_intel_crtc(plane_state->crtc);
> > +		new_planes = true;
> >  
> >  		if (!intel_plane_state->base.visible)
> >  			continue;
> > @@ -1084,7 +1086,7 @@ void intel_fbc_choose_crtc(struct
> > drm_i915_private *dev_priv,
> >  		break;
> >  	}
> >  
> > -	if (!crtc_chosen)
> > +	if (new_planes && !crtc_chosen)
> >  		fbc->no_fbc_reason = "no suitable CRTC for FBC";
> >  
> >  out:
> > -- 
> > 2.11.0
> > 
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