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

From: Jani Nikula <jani.nikula@linux.intel.com>
To: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org, stable@vger.kernel.org
Subject: Re: [PATCH] drm/i915: Disable FBC on Haswell
Date: Mon, 09 Jun 2014 22:06:29 +0300	[thread overview]
Message-ID: <87k38phphm.fsf@intel.com> (raw)
In-Reply-To: <20140609183630.GV27580@intel.com>

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

BR,
Jani.

>
> -- 
> Ville Syrjälä
> Intel OTC

-- 
Jani Nikula, Intel Open Source Technology Center
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