Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754898AbbGCPL3 (ORCPT ); Fri, 3 Jul 2015 11:11:29 -0400 Received: from netrider.rowland.org ([192.131.102.5]:49803 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755211AbbGCPLU (ORCPT ); Fri, 3 Jul 2015 11:11:20 -0400 Date: Fri, 3 Jul 2015 11:11:19 -0400 (EDT) From: Alan Stern X-X-Sender: stern@netrider.rowland.org To: Tomeu Vizoso cc: "linux-pm@vger.kernel.org" , Laurent Pinchart , Dmitry Torokhov , "Rafael J. Wysocki" , Len Brown , Pavel Machek , Greg Kroah-Hartman , Ulf Hansson , Kevin Hilman , Russell King , Krzysztof Kozlowski , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v3 2/2] PM / Runtime: Add pm_runtime_enable_recursive In-Reply-To: Message-ID: 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 Content-Length: 1768 Lines: 40 On Fri, 3 Jul 2015, Tomeu Vizoso wrote: > >> Yeah, that would remove the need for messing with the runtime PM > >> enable status of descendant devices, but I wonder why Rafael went that > >> way initially. > > > > I forget the details. Probably it was just to be safe. We probably > > thought that if a device was disabled for runtime PM then its runtime > > PM status might not be accurate. But if direct_complete is set then it > > may be reasonable to assume that the runtime PM status _is_ accurate. > > Cool. > > Rafael and I briefly discussed ignore_children while the original > > direct_complete patch was being designed. We didn't come to any > > definite conclusion and decided to forget about it for the time being. > > Maybe now would be a good time to reconsider it. > > I would prefer to have ignore_children ignore whether the children of > a device were able to do direct_complete, rather than having a > direct_complete_default flag (plus not requiring that all its > descendants have runtime PM enabled). Okay, but remember that sometimes these "virtual" devices will exist beneath a device that needs to have ignore_children off. So this won't be a complete solution to your problem. Let's see what Rafael thinks about these two issues. It seems to me that the hardest part is dealing with drivers/subsystems that have no runtime PM support. In such cases, we have to be very careful not to use direct_complete unless we know that the device does no power management at all. Alan Stern -- 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/