On Fri, 22 Aug 2014, Eric Rannaud <eric.rann...@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 <ch...@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. BR, Jani. -- Jani Nikula, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
