[Intel-gfx] i915: Regression: +4W in idle power use on Macbook Pro 15 (late 2013)

[Sean V Kelley]

On Mon, Aug 25, 2014 at 3:22 AM, Jani Nikula <jani.nikula at intel.com> wrote:

>
> [just moving from lkml to intel-gfx for a better fitting audience]
>
> On Mon, 25 Aug 2014, Jani Nikula <jani.nikula at intel.com> wrote:
> > On Fri, 22 Aug 2014, Eric Rannaud <eric.rannaud at gmail.com> wrote:
> >> Hi,
> >>
> >> Between 3.15.4 and 3.15.8, there was an increase in idle power
> consumption on
> >> Apple Macbook Pro 15 (late 2013) on a freshly booted system (no wifi
> driver
> >> loaded; brightness set to 4/100; X running; no desktop environment,
> except
> >> Awesome), from 6.5W to about 10.5W, as reported by powertop.
> >>
> >> In the stable tree, it bisects to:
> >>         commit f4db98240ac2c6d9d2118c6f82d483ff5293f1ed
> >>         Author: Chris Wilson <chris at chris-wilson.co.uk>
> >>         Date:   Fri Jun 6 10:37:11 2014 +0100
> >>
> >>             drm/i915: Disable FBC by default also on Haswell and later
> >>
> >>             commit 0368920e51ae0cded0eb518c340a4dd17764d461 upstream.
> >>
> >>             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.
> >>
> >> The issue is still present in Linus' tree (v3.17-rc1-22-g480cadc2b7e0).
> >>
> >> With a 75Wh battery, that's a significant loss in battery life in
> normal use.
> >>
> >> I'll be happy to help test any potential fix.
> >
> > The earlier regression trumps, and in this case it was enabling FBC by
> > default on Haswell. Sorry.
> >
> > You can enable FBC with i915.enable_fbc=1 module parameter, but all bets
> > are off. See the commit message you quoted above. I don't recommend.
> >
>


For what it's worth, I have a Mid-2014, Macbook Pro Retina (13inch
display), running Archlinux with 3.16.

Definitely, enable_fbc is a win for me and I do manually enable it.  But I
am still seeing what I believe to be
a regression overall of about +4W even with fbc enabled.  Still digging for
clues.

Sean





-- 
Sean V. Kelley <sean.v.kelley at intel.com>
Open Source Technology Center / SSG
Intel Corp.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/intel-gfx/attachments/20140828/d4c3ae7d/attachment.html>