Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753944Ab1FMS4B (ORCPT ); Mon, 13 Jun 2011 14:56:01 -0400 Received: from smtp-out.google.com ([74.125.121.67]:38184 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750864Ab1FMSz7 convert rfc822-to-8bit (ORCPT ); Mon, 13 Jun 2011 14:55:59 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=yRPmyJjIU5vwi+W5hFhJYj3AGhV8JJ/r0r95mHCfWSwaHnRXDd1t6v4czRc2Ej5UpZ grDEmTTD6f63E/NQ+YOA== MIME-Version: 1.0 In-Reply-To: <201106132037.49009.rjw@sisk.pl> References: <1307925825-28566-1-git-send-email-ccross@android.com> <201106132037.49009.rjw@sisk.pl> Date: Mon, 13 Jun 2011 11:55:40 -0700 X-Google-Sender-Auth: SFN8_x_JZpjrHwcmMTyCysgZ_jM Message-ID: Subject: Re: [PATCH 0/3] CPU PM notifiers From: Colin Cross To: "Rafael J. Wysocki" Cc: "linux-arm-kernel@lists.infradead.org" , lkml , Russell King , Catalin Marinas , Santosh Shilimkar , Linux PM mailing list Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2762 Lines: 61 On Mon, Jun 13, 2011 at 11:37 AM, Rafael J. Wysocki wrote: > On Monday, June 13, 2011, Colin Cross wrote: >> This patch set tries to address Russell's concerns with platform >> pm code calling into the driver for every block in the Cortex A9s >> during idle, hotplug, and suspend. ?The first patch adds cpu pm >> notifiers that can be called by platform code, the second uses >> the notifier to save and restore the GIC state, and the third >> saves the VFP state. >> >> The notifiers are used for two types of events, CPU PM events and >> CPU complex PM events. ?CPU PM events are used to save and restore >> per-cpu context when a single CPU is preparing to enter or has >> just exited a low power state. ?For example, the VFP saves the >> last thread context, and the GIC saves banked CPU registers. >> >> CPU complex events are used after all the CPUs in a power domain >> have been prepared for the low power state. ?The GIC uses these >> events to save global register state. >> >> Platforms that call the cpu_pm APIs must select >> CONFIG_ARCH_USES_CPU_PM >> >> L2 cache is not covered by this patch set, as the determination >> of when the L2 is reset and when it is retained is >> platform-specific, and most of the APIs necessary are already >> present. >> >> ?arch/arm/Kconfig ? ? ? ? ? ? ?| ? ?7 ++ >> ?arch/arm/common/gic.c ? ? ? ? | ?212 +++++++++++++++++++++++++++++++++++++++++ >> ?arch/arm/include/asm/cpu_pm.h | ? 54 +++++++++++ >> ?arch/arm/kernel/Makefile ? ? ?| ? ?1 + >> ?arch/arm/kernel/cpu_pm.c ? ? ?| ?181 +++++++++++++++++++++++++++++++++++ > > Is there any reason why this has to be ARM-specific? ?There are other > architectures where this kind of feature might make sense (SH and > powerpc at least). Nothing other than there are currently no adaptations for any drivers besides ARM, but I can move it somewhere outside ARM. Any suggestions where? > Besides, is there any overlap between this feature and the CPU hotplug > notifiers? I don't think so - the hotplug notifiers are used when a CPU is being removed from the system, so no saving and restoring is necessary - the CPU will be rebooted from scratch. They are used by systems outside the CPU that need to know that a CPU no longer exists. CPU PM notifiers are used when a CPU is going through reset in a way that should be transparent to most of the system. Only drivers within the CPU itself need a notification. Note that both ARM drivers I modified did not have a register_cpu_notifier call. > Rafael > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/