From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Li, Aubrey" Subject: Re: [PATCH] PM / suspend: Always use deepest C-state in the "freeze" sleep state Date: Mon, 12 May 2014 22:19:08 +0800 Message-ID: <5370D85C.3090505@linux.intel.com> References: <2548502.zJ1no3NhRc@vostro.rjw.lan> <5370D5E4.5040001@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mga02.intel.com ([134.134.136.20]:62445 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756705AbaELOUY (ORCPT ); Mon, 12 May 2014 10:20:24 -0400 In-Reply-To: <5370D5E4.5040001@linaro.org> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Daniel Lezcano , "Rafael J. Wysocki" , Linux PM list Cc: Linux Kernel Mailing List , Zhang Rui , Aubrey Li On 2014/5/12 22:08, Daniel Lezcano wrote: > On 05/05/2014 12:51 AM, Rafael J. Wysocki wrote: >> From: Rafael J. Wysocki >> >> If freeze_enter() is called, we want to bypass the current cpuidle >> governor and always use the deepest available (that is, not disabled) >> C-state, because we want to save as much energy as reasonably possible >> then and runtime latency constraints don't matter at that point, since >> the system is in a sleep state anyway. >> >> Signed-off-by: Rafael J. Wysocki >> --- >> >> This is on top of https://patchwork.kernel.org/patch/4071541/ . >> > > Wouldn't make sense to revisit play_dead instead ? > play_dead() is broken. Even if it works, we still should rely on cpuidle driver to place the CPUs into the deepest c-state, because there is no architectural way to enter deepest c-state and what play_dead() does is a bad assumption. Thanks, -Aubrey