Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932282Ab2BMUqv (ORCPT ); Mon, 13 Feb 2012 15:46:51 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:50441 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932255Ab2BMUqt (ORCPT ); Mon, 13 Feb 2012 15:46:49 -0500 From: "Rafael J. Wysocki" To: Alan Stern Subject: Re: [RFC PATCH 4/6] PM / Runtime: Introduce flag can_power_off Date: Mon, 13 Feb 2012 21:50:41 +0100 User-Agent: KMail/1.13.6 (Linux/3.3.0-rc3+; KDE/4.6.0; x86_64; ; ) Cc: Lin Ming , Zhang Rui , Jeff Garzik , Tejun Heo , Len Brown , linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org, linux-pm@vger.kernel.org References: In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201202132150.42115.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2365 Lines: 49 On Monday, February 13, 2012, Alan Stern wrote: > On Mon, 13 Feb 2012, Rafael J. Wysocki wrote: > > > > I'm not sure if this is really the right approach. What you're trying > > > to do is implement two different low-power states, basically D3hot and > > > D3cold. Currently the runtime PM core doesn't support such things; all > > > it knows about is low power and full power. > > > > I'd rather say all it knows about is "suspended" and "active", which mean > > "the device is not processing I/O" and "the device may be processing I/O", > > respectively. A "suspended" device may or may not be in a low-power state, > > but the runtime PM core doesn't care about that. > > Yes, okay. We can say that this patch tries to implement two different > "suspended" states, basically "low power" and "power off" (or D3hot and > D3cold). > > > > Before doing an ad-hoc implementation, it would be best to step back > > > and think about other subsystems. Other sorts of devices may well have > > > multiple low-power states. What's the best way for this to be > > > supported by the PM core? > > > > Well, I honestly don't think there's any way they all can be covered at the > > same time and that's why we chose to support only "suspended" and "active" > > as defined above. The handling of multiple low-power states must be > > implemented outside of the runtime PM core (like in the PCI core, for example). > > That's the point. If this is to be implemented outside of the runtime > PM core, should the patch be allowed to add new fields to struct > dev_pm_info (which has to be shared among all subsystems)? > > Or to put it another way, if we do add new fields to struct dev_pm_info > (like can_power_off) in order to help support multiple "suspended" > states, shouldn't these new fields be such that they can be used by > many different subsystems rather than being special for the > full-power/no-power situation? > > Likewise, should new routines like pm_runtime_allow_power_off() be > added to the runtime PM core if they are going to be used just by PCI? No, they shouldn't. Thanks, 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/