[Intel-gfx] [PATCH] drm/i915/skl: Assume no scaling is available when things are not as expected

[Konduru, Chandra]

> >
> > Cdclk < crtc_clock is not allowed and suggests a different problem elsewhere.
> >
> > It is more robust and safe to assume no scaling is possible in this case.
> >
> > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_display.c
> b/drivers/gpu/drm/i915/intel_display.c
> > index 93a5e51..4c99373 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -13234,7 +13234,7 @@ skl_max_scale(struct intel_crtc *intel_crtc, struct
> intel_crtc_state *crtc_state
> >  	crtc_clock = crtc_state->base.adjusted_mode.crtc_clock;
> >  	cdclk = dev_priv->display.get_display_clock_speed(dev);
> 
> Probably fallout from the in-flight dynamic cdclk stuff - this code checks
> the wrong bits I guess. Chandra?

Looks like something elsewhere has fallen out and issue manifested here.

Damien reported another issue where get_display_clock_speed causing 
an assert because it is called when dev_priv->pm.suspend is true during
runtime resume. But later  was resolved after one of atomic patch is 
reverted.

While Maarten is addressing recently reported atomic issues, for 
time being some atomic crtc patches were reverted.

I am not 100% sure whether issue here is due to same root cause or 
due to something different.

> 
> Thanks, Daniel
> 
> >
> > -	if (!crtc_clock || !cdclk)
> > +	if (!crtc_clock || !cdclk || (cdclk < crtc_clock))
> >  		return DRM_PLANE_HELPER_NO_SCALING;
> >
> >  	/*
> > --
> > 2.4.0
> >
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> > Intel-gfx at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch