From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sylwester Nawrocki Subject: Re: [PATCH RFC v3 1/2] PM / Domains: Extend API pm_genpd_dev_need_restore to use restore types Date: Thu, 18 Dec 2014 11:05:18 +0100 Message-ID: <5492A6DE.5020704@samsung.com> References: <1418489518-7252-1-git-send-email-amit.daniel@samsung.com> <7h4msub0ca.fsf@deeprootsystems.com> <5418986.E58ik2Q1Hm@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-reply-to: <5418986.E58ik2Q1Hm@vostro.rjw.lan> Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" , Kevin Hilman Cc: amit daniel kachhap , Marek Szyprowski , LAK , "linux-samsung-soc@vger.kernel.org" , Len Brown , Ulf Hansson , Tomasz Figa , Kukjin Kim , Thomas Abraham , Pankaj Dubey , Geert Uytterhoeven , "linux-pm@vger.kernel.org" , "linux-kernel@vger.kernel.org" List-Id: linux-pm@vger.kernel.org On 18/12/14 01:58, Rafael J. Wysocki wrote: >>>> What's needed to solve this problem is a generalized way to have runtime >>>> > >> PM dependencies between devices. Runtime PM already automatically >>>> > >> handles parent devices as one type of dependent device (e.g. a parent >>>> > >> device needs to be runtime PM resumed before its child.) So what's >>>> > >> needed is a generic way to other PM dependencies with the runtime PM >>>> > >> core (not the genpd core.) >>> > > >>> > > Considering the example above with three devices, device D1 and D2 are >>> > > passive components in this power domain. These devices only need to >>> > > know the state changes of the power domains but would not control the >>> > > power domain themselves nor put forth constraints in the power domain >>> > > state changes. So I did not clearly understand as to how this example >>> > > could be solved by introducing changes in runtime PM core. >> > >> > Your solution only solves the problems for devices managed by genpd. >> > >> > If I understood your example correctly, what you really want to solve >> > this problem more generically is to be able to tell the runtime PM core >> > that D3 has a dependency on D1 and D2. Then, whenver the runtime PM >> > core is doing get/put operations for D3, it needs to also do them for D1 >> > and D2. Indeed, I think it would solve most of the problems if we were able to model the PM dependencies between devices which would then be handled in the PM core. I recall something like this has been proposed a while ago [1]. >> > This will accomplish the same as your proposed approach, but work for >> > any devices in any PM domains. > > Plus, it is not limited to runtime PM, really. It affects system suspend > too. [1] https://lkml.org/lkml/2009/8/26/485 -- Regards, Sylwester