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

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 10 Jun 2014, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Mon, Jun 09, 2014 at 10:06:29PM +0300, Jani Nikula wrote:
>> On Mon, 09 Jun 2014, Ville Syrjälä <ville.syrjala@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@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@jonkri.com>
>> >> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>> >> > Cc: stable@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 ;-)

Pushed to -fixes with a little more verbose change. Thanks for the patch
and review.

BR,
Jani.


> -Daniel
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch

-- 
Jani Nikula, Intel Open Source Technology Center