From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH v2] ahci: Allow setting a default LPM policy for mobile chipsets Date: Mon, 11 Dec 2017 08:54:04 -0800 Message-ID: <20171211165404.GM2421075@devbig577.frc2.facebook.com> References: <20171211165216.5604-1-hdegoede@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-qt0-f193.google.com ([209.85.216.193]:38617 "EHLO mail-qt0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752437AbdLKQyI (ORCPT ); Mon, 11 Dec 2017 11:54:08 -0500 Content-Disposition: inline In-Reply-To: <20171211165216.5604-1-hdegoede@redhat.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Hans de Goede Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org On Mon, Dec 11, 2017 at 05:52:16PM +0100, Hans de Goede wrote: > On many laptops setting a different LPM policy then unknown / > max_performance can lead to power-savings of 1.0 - 1.5 Watts (when idle). > > Modern ultrabooks idle around 6W (at 50% screen brightness), 1.0 - 1.5W > is a significant chunk of this. > > There are some performance / latency costs to enabling LPM by default, > so it is desirable to make it possible to set a different LPM policy > for mobile / laptop variants of chipsets / "South Bridges" vs their > desktop / server counterparts. Also enabling LPM by default is not > entirely without risk of regressions. At least min_power is known to > cause issues with some disks, including some reports of data corruption. > > This commits adds a new ahci.mobile_lpm_policy kernel cmdline option, > which defaults to a new SATA_MOBILE_LPM_POLICY Kconfig option so that > Linux distributions can choose to set a LPM policy for mobile chipsets > by default. > > The reason to have both a kernel cmdline option and a Kconfig default > value for it, is to allow easy overriding of the default to allow > trouble-shooting without needing to rebuild the kernel. > > Signed-off-by: Hans de Goede Applied to libata/for-4.16. Thanks, Hans. -- tejun