From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jani Nikula Subject: Re: i915: Regression: +4W in idle power use on Macbook Pro 15 (late 2013) Date: Mon, 25 Aug 2014 13:22:05 +0300 Message-ID: <87sikklvhu.fsf@intel.com> References: <87vbpglvmu.fsf@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by gabe.freedesktop.org (Postfix) with ESMTP id 022E46E337 for ; Mon, 25 Aug 2014 03:22:11 -0700 (PDT) In-Reply-To: <87vbpglvmu.fsf@intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: Eric Rannaud , "intel-gfx@lists.freedesktop.org" Cc: Daniel Vetter , Jon Kristensen , Greg Kroah-Hartman List-Id: intel-gfx@lists.freedesktop.org [just moving from lkml to intel-gfx for a better fitting audience] On Mon, 25 Aug 2014, Jani Nikula wrote: > On Fri, 22 Aug 2014, Eric Rannaud 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 >> 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 -- Jani Nikula, Intel Open Source Technology Center