From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752468AbaELXhG (ORCPT ); Mon, 12 May 2014 19:37:06 -0400 Received: from v094114.home.net.pl ([79.96.170.134]:55766 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751681AbaELXhD (ORCPT ); Mon, 12 May 2014 19:37:03 -0400 From: "Rafael J. Wysocki" To: Daniel Lezcano Cc: "Li, Aubrey" , Linux PM list , Linux Kernel Mailing List , Zhang Rui , Aubrey Li Subject: Re: [PATCH] PM / suspend: Always use deepest C-state in the "freeze" sleep state Date: Tue, 13 May 2014 01:53:49 +0200 Message-ID: <1675732.Zj8pe2mRTV@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/3.14.0-rc7+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <5370E026.5040105@linaro.org> References: <2548502.zJ1no3NhRc@vostro.rjw.lan> <5370D85C.3090505@linux.intel.com> <5370E026.5040105@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, May 12, 2014 04:52:22 PM Daniel Lezcano wrote: > On 05/12/2014 04:19 PM, Li, Aubrey wrote: > > 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. > > Ok, let me rephrase it. Why not revisiting cpuidle_play_dead instead ? Many drivers don't implement the ->enter_dead() callback. -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.