From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753383Ab0EEXmg (ORCPT ); Wed, 5 May 2010 19:42:36 -0400 Received: from smtp-out.google.com ([216.239.44.51]:43310 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751797Ab0EEXme convert rfc822-to-8bit (ORCPT ); Wed, 5 May 2010 19:42:34 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=mime-version:in-reply-to:references:date:message-id:subject:from:to: cc:content-type:content-transfer-encoding:x-system-of-record; b=OK8uVQKFTQZD+2sQQHOa3c7+sc3DPcFj4pATUV0iOov1ZrhKjAYMtc2FfN74Tbguk OfyLWhjLs0AsdTMkzQdBw== MIME-Version: 1.0 In-Reply-To: <87fx26ymrf.fsf@deeprootsystems.com> References: <87fx26ymrf.fsf@deeprootsystems.com> Date: Wed, 5 May 2010 16:42:29 -0700 Message-ID: Subject: Re: [PATCH 0/8] Suspend block api (version 6) From: Brian Swetland To: Kevin Hilman Cc: Alan Stern , Matthew Garrett , Mark Brown , "Rafael J. Wysocki" , =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= , linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Tejun Heo , Oleg Nesterov , Paul Walmsley , magnus.damm@gmail.com, mark gross , Arjan van de Ven , Geoff Smith Content-Type: text/plain; charset=UTF-8 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 On Wed, May 5, 2010 at 4:03 PM, Kevin Hilman wrote: > > I guess what we're talking about here is a set of per-device > constraints that could be used by both [opportunistic|system] suspend > and runtime PM.  For lack of a better term, per-device PM QoS (as > compared to the current system-wide PM QoS.) > > For example, if userspace (or some other device) has communicated that > it has a constraint on the audio HW, then both the suspend path and the > runtime PM path could check those constraints before making a decision > on how to act.  Hopefully the phone app would set a constraint and the > cow-noise app would not.  :) > > On OMAP, we keep track of per-device constraints (currently latency > and throughput) in order to make proper run-time PM decicions in the > kernel, but we are realizing that we need a way for userspace to > communicate these constraints as well, so that userspace can make > power vs. performance policy decisions instead of the kernel. > > Probably generalizing these into the LDM is the direction to go so > userspace can set constraints on a per-device (or per-class?) basis: > > /sys/devices/.../power/constraint/throughput > /sys/devices/.../power/constraint/wakeup_latency > /sys/devices/.../power/constraint/... ? The constraint stuff is definitely something I'd love to talk about in detail. It's a problem that I think is common to every SoC I've worked with. Having a general solution for this problem (of specifying and observing various constraints for clock, power, qos, etc) kernel-wide would seem like a big win. Might be worth kicking some design ideas around and getting a bunch of the interested parties together at some of the upcoming linux conference things this fall on the east coast? Brian