[Intel-gfx] [PATCH] drm/i915: Disable FBC on Haswell

[Ville Syrjälä]

On Mon, Jun 09, 2014 at 09:12:18PM +0300, Jani Nikula wrote:
> On Fri, 06 Jun 2014, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > It causes black screen on bootup and is approximately 100x slower than
> > running with FBC disabled, so the GPU runs at a high frequency for much
> > longer - completely contrary to the power saving claims. It also still
> > has mutex deadlocks in multi-head scenarios, which can lead to a
> > system/X lockup. These bugs were known before FBC was enabled by default
> > on Haswell and still have not been fixed.
> >
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79716
> > Reported-and-tested-by: Jon Kristensen <info at jonkri.com>
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: stable at vger.kernel.org
> > ---
> >  drivers/gpu/drm/i915/intel_pm.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index e403010540a5..0b8a6010427e 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -511,8 +511,7 @@ void intel_update_fbc(struct drm_device *dev)
> >  	obj = intel_fb->obj;
> >  	adjusted_mode = &intel_crtc->config.adjusted_mode;
> >  
> > -	if (i915.enable_fbc < 0 &&
> > -	    INTEL_INFO(dev)->gen <= 7 && !IS_HASWELL(dev)) {
> > +	if (i915.enable_fbc < 0) {
> 
> Not only does this disable FBC by default on Haswell but also on all
> current and future platforms, including Broadwell. Shouldn't you leave
> the INTEL_INFO(dev)->gen <= 7 part intact?

The current FBC code is universally broken.

-- 
Ville Syrjälä
Intel OTC