From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751807Ab1GGWeo (ORCPT ); Thu, 7 Jul 2011 18:34:44 -0400 Received: from na3sys009aog124.obsmtp.com ([74.125.149.151]:46901 "EHLO na3sys009aog124.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751632Ab1GGWen (ORCPT ); Thu, 7 Jul 2011 18:34:43 -0400 From: Kevin Hilman To: Todd Poynor Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Russell King , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Colin Cross Subject: Re: [PATCH 0/3] Add generic idle notifiers Organization: Texas Instruments, Inc. References: <1309229190-25006-1-git-send-email-toddpoynor@google.com> <87ei22dnsp.fsf@ti.com> <20110707201748.GB32199@google.com> Date: Thu, 07 Jul 2011 15:34:38 -0700 In-Reply-To: <20110707201748.GB32199@google.com> (Todd Poynor's message of "Thu, 7 Jul 2011 13:17:48 -0700") Message-ID: <87tyaxd8jl.fsf@ti.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Todd Poynor writes: > On Thu, Jul 07, 2011 at 10:05:10AM -0700, Kevin Hilman wrote: >> Todd Poynor writes: >> >> > Add notifiers for idle entry and exit, called with IDLE_START when a >> > CPU goes idle and IDLE_END when it goes out of idle, based on the >> > existing idle notifiers for the x86_64 arch. >> > >> > Convert x86_64 to use these notifiers, and call the notifiers on ARM. >> > >> > Convert the ARM LEDs events for idle start/end to these notifiers. >> >> Is this intended to replace the more general CPU PM notifiers proposed >> by Colin: >> >> http://lists.infradead.org/pipermail/linux-arm-kernel/2011-June/052827.html > > This is intended to coexist with the CPU PM notifiers. The idle > notifiers proposed here are notifying of a change in kernel scheduler > state: the scheduler has no task to run and is entering its "idle > loop", or now has something to run and is exiting idle state. > Things that can use this include power management hints such as the > existing drivers/idle/i7300_idle.c usage, the ARM LEDs idle triggers, > and there's probably other existing potential uses in other arch'es that > I should go track down. > > The CPU PM notifiers notify of changes in hardware power state that > affect the CPU and closely associated IP blocks (such as an OMAP > power state transition that causes one or more CPU power domains to > hit OFF). These changes may be due to cpuidle power state management > when the system is idle, or may be due to suspending or resuming the > system (such as a suspend-to-RAM), or may be due to a CPU hotplug event. > In the case of an idle loop entry, if cpuidle decides it is not > appropriate to change CPU power state (as when insufficient time > remains until next timer expiry to enter such a power state due to > entry and exit latency), there may be no CPU PM notification > generated. The callbacks for CPU PM notifiers on ARM do things such > as save/restore GIC interrupt controller state and VFP floating-point > coprocessor state. > > That's the intent, anyhow, but ideas are welcome, thanks, OK, thanks for the clarification. Kevin