From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752377AbdLFPlR (ORCPT ); Wed, 6 Dec 2017 10:41:17 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36290 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751362AbdLFPlN (ORCPT ); Wed, 6 Dec 2017 10:41:13 -0500 From: Hans de Goede To: Tejun Heo Cc: Hans de Goede , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 0/3] ahci: Allow setting a default LPM policy for mobile chipsets Date: Wed, 6 Dec 2017 16:41:07 +0100 Message-Id: <20171206154110.11548-1-hdegoede@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Wed, 06 Dec 2017 15:41:13 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi All, 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. This series 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. I realize that this series will not be entirely uncontroversial, 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. But this series only adds a Kconfig option to allow distributions to select a different LPM policy for mobile chipsets if they which to do so, the default value is unchanged from before. I've done a blog-post a while ago to ask users to test this and specifically the new med_power_with_dipm option which mirrors the Intel RST Windows drivers defaults: https://hansdegoede.livejournal.com/18412.html Test results from this can be found here: https://fedoraproject.org/wiki/Changes/ImprovedLaptopBatteryLife#How_To_Test All testing sofar has shown that the med_power_with_dipm option seems to be safe, even with SSDs which are known to corrupt data with the min_power setting. Taking this into account, one thing to consider is the following change to the Kconfig changes in the last patch in the series: config SATA_MOBILE_LPM_POLICY int "Default SATA Link Power Management policy for mobile chipsets" - range 0 4 + range 0 3 default 0 depends on SATA_AHCI help Thus effectively forbidding choosing min_power as default at the Kconfig level. Regards, Hans