From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755167AbaHYKTL (ORCPT ); Mon, 25 Aug 2014 06:19:11 -0400 Received: from mga01.intel.com ([192.55.52.88]:44079 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755142AbaHYKTJ (ORCPT ); Mon, 25 Aug 2014 06:19:09 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.04,396,1406617200"; d="scan'208";a="589438581" From: Jani Nikula To: Eric Rannaud , Linux Kernel Cc: Chris Wilson , Jon Kristensen , Daniel Vetter , Greg Kroah-Hartman Subject: Re: i915: Regression: +4W in idle power use on Macbook Pro 15 (late 2013) In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: User-Agent: Notmuch/0.18.1+66~g7487985 (http://notmuchmail.org) Emacs/23.4.1 (x86_64-pc-linux-gnu) Date: Mon, 25 Aug 2014 13:19:05 +0300 Message-ID: <87vbpglvmu.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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