From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Rannaud Subject: Re: i915: Regression: +4W in idle power use on Macbook Pro 15 (late 2013) Date: Mon, 25 Aug 2014 05:19:49 -0700 Message-ID: References: <87vbpglvmu.fsf@intel.com> <87sikklvhu.fsf@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-we0-f179.google.com (mail-we0-f179.google.com [74.125.82.179]) by gabe.freedesktop.org (Postfix) with ESMTP id D7D4D89FA5 for ; Mon, 25 Aug 2014 05:19:50 -0700 (PDT) Received: by mail-we0-f179.google.com with SMTP id u57so13301603wes.10 for ; Mon, 25 Aug 2014 05:19:49 -0700 (PDT) In-Reply-To: <87sikklvhu.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: Jani Nikula Cc: Daniel Vetter , Jon Kristensen , "intel-gfx@lists.freedesktop.org" , Greg Kroah-Hartman List-Id: intel-gfx@lists.freedesktop.org Hi Jani, Is there a way to restore the prior lower power consumption when idling? As I understand it, FBC should not have a direct effect on power consumption when idle, only when the FB is actively refreshed. Is it understood why no FBC would have such a dramatic impact (+4W) on a system sitting idle? I'm aware of i915.i915_enable_rc6=1 and i915.lvds_downclock=1, which I haven't yet tried. Is there anything else I should also try? Thanks, Eric On Mon, Aug 25, 2014 at 3:22 AM, Jani Nikula wrote: > > [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