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

[Daniel Vetter]

On Mon, Jun 09, 2014 at 10:06:29PM +0300, Jani Nikula wrote:
> On Mon, 09 Jun 2014, Ville Syrjälä <ville.syrjala at linux.intel.com> wrote:
> > 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.
> 
> Well, then the commit message should reflect that! :p

s/Haswell/Haswell+/ and it's correct ;-)
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch