From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH] libata: Add new med_power_with_dipm link_power_management_policy setting Date: Mon, 18 Sep 2017 20:23:42 -0700 Message-ID: <20170919032341.GM378890@devbig577.frc2.facebook.com> References: <20170914103536.7650-1-hdegoede@redhat.com> <20170914103536.7650-2-hdegoede@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-qt0-f177.google.com ([209.85.216.177]:51734 "EHLO mail-qt0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750882AbdISDXq (ORCPT ); Mon, 18 Sep 2017 23:23:46 -0400 Content-Disposition: inline In-Reply-To: <20170914103536.7650-2-hdegoede@redhat.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Hans de Goede Cc: Matthew Garrett , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org On Thu, Sep 14, 2017 at 12:35:36PM +0200, Hans de Goede wrote: > As described by Matthew Garret quite a while back: > https://mjg59.dreamwidth.org/34868.html > > Intel CPUs starting with the Haswell generation need SATA links to power > down for the "package" part of the CPU to reach low power-states like > PC7 / P8 which bring a significant power-saving with them. > > The default max_performance lpm policy does not allow for these high > PC states, both the medium_power and min_power policies do allow this. > > The min_power policy saves significantly more power, but there are some > reports of some disks / SSDs not liking min_power leading to system > crashes and in some cases even data corruption has been reported. > > Matthew has found a document documenting the default settings of > Intel's IRST Windows driver with which most laptops ship: > https://www-ssl.intel.com/content/dam/doc/reference-guide/sata-devices-implementation-recommendations.pdf > > Matthew wrote a patch changing med_power to match those defaults, but > that never got anywhere as some people where reporting issues with the > patch-set that patch was a part of. > > This commit is another attempt to make the default IRST driver settings > available under Linux, but instead of changing medium_power and > potentially introducing regressions, this commit adds a new > med_power_with_dipm setting which is identical to the existing > medium_power accept that it enables dipm on top, which makes it match > the Windows IRST driver settings, which should hopefully be safe to > use on most devices. > > The med_power_with_dipm setting is close to min_power, except that: > a) It does not use host-initiated slumber mode (ASP not set), > but it does allow device-initiated slumber > b) It does not enable DevSlp mode > > On my T440s test laptop I get the following power savings when idle: > medium_power 0.9W > med_power_with_dipm 1.2W > min_power 1.2W > > Suggested-by: Matthew Garrett > Cc: Matthew Garrett > Signed-off-by: Hans de Goede Applied to libata/for-4.15. Thanks. -- tejun