From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754322Ab2JPGzw (ORCPT ); Tue, 16 Oct 2012 02:55:52 -0400 Received: from mailout3.samsung.com ([203.254.224.33]:16040 "EHLO mailout3.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754035Ab2JPGzv (ORCPT ); Tue, 16 Oct 2012 02:55:51 -0400 X-AuditID: cbfee60c-b7f876d000006a6e-d6-507d01566f1f Date: Tue, 16 Oct 2012 06:40:22 +0000 (GMT) From: MyungJoo Ham Subject: Re: Re: [PATCH v4 2/3] devfreq: Add suspend and resume apis To: "Rafael J. Wysocki" Cc: Rajagopal Venkat , "mturquette@linaro.org" , =?euc-kr?Q?=B9=DA=B0=E6=B9=CE?= , "patches@linaro.org" , "linaro-dev@lists.linaro.org" , "linux-pm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , =?euc-kr?Q?=C0=CC=C1=BE=C8=AD?= Reply-to: myungjoo.ham@samsung.com MIME-version: 1.0 X-MTR: 20121016063949084@myungjoo.ham Msgkey: 20121016063949084@myungjoo.ham X-EPLocale: ko_KR.euc-kr X-Priority: 3 X-EPWebmail-Msg-Type: personal X-EPWebmail-Reply-Demand: 0 X-EPApproval-Locale: X-EPHeader: ML X-EPTrCode: X-EPTrName: X-MLAttribute: X-RootMTR: 20121016063949084@myungjoo.ham X-ParentMTR: X-ArchiveUser: X-CPGSPASS: N Content-type: text/plain; charset=euc-kr MIME-version: 1.0 Message-id: <12788576.101631350369619343.JavaMail.weblogic@epml27> X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrBIsWRmVeSWpSXmKPExsVy+t/tmbphjLUBBueXy1lc3jWHzYHR4/Mm uQDGKC6blNSczLLUIn27BK6Mr0fKC1bIVdw818rewHhAtouRk0NIQF1i0ZKTbCC2hICJxL1j vewQtpjEhXvr2SBq5jNKXJxpDWKzCKhKzN1wkrGLkYODTUBPYubnZBBTWMBF4s9pI5AKEaCK LU/+A03h4mAWOMcs8a1hLivEGCWJNftesYDYvAKCEidnPmGBWAU0sushK0RcTeLLvdtMEHEJ iVnTL7BC2LwSM9qfQtXLSUz7uoYZwpaWOD9rAyPMyYu/P4aK80scu72DCeQ2kN4n94Nhxuze /AXqWwGJqWcOQrVqSVz/AHMOn8SahW9ZYMbsOrWcGab3/pa5YKcxCyhKTOl+yA5ha0l8+bGP DdVbHEC2k8Sv66oTGOVmIcnMQtI9C0k3spoFjCyrGEVTC5ILipPSU430ihNzi0vz0vWS83M3 MYLj+xnPDsY5DRaHGAU4GJV4eDXCagKEWBPLiitzDzFKcDArifB6TAQK8aYkVlalFuXHF5Xm pBYfYpTmYFES563zSAkQEkhPLEnNTk0tSC2CyTJxcEoBk8X5W1YVXuyTWB2eXiw8+KCtVfzN 10+3zb9lz76j3t23bHtQegc3Z3D6tx/CwgWn40yUnuwX9hH5Gm1YlbBFXfXxVm02/5OO8sym 658fdg/P+PtGZNtk09zTTZJ8E7lS47ZJ3OA+ef1ZbcaB2spd809efvOQxc3wubvBTt8Dn2+d W/LkWZXNUiWW4oxEQy3mouJEAELw7P7rAgAA Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id q9G6twJf029966 > On Monday 08 of October 2012 10:48:24 MyungJoo Ham wrote: > > > On 8 October 2012 03:31, Rafael J. Wysocki wrote: > > > > On Thursday 04 of October 2012 14:58:33 Rajagopal Venkat wrote: > > > >> Add devfreq suspend/resume apis for devfreq users. This patch > > > >> supports suspend and resume of devfreq load monitoring, required > > > >> for devices which can idle. > > > >> > > > >> Signed-off-by: Rajagopal Venkat > > > >> Acked-by: MyungJoo Ham > > > > > > > > Well, I wonder if this may be tied in to the runtime PM framework, so that, > > > > for example, pm_runtime_suspend() will automatically suspend devfreq on > > > > success (and the runtime resume of the device will resume devfreq)? > > > > > > That's a good idea. If you agree, we can handle this as separate patch on > > > top this patchset. > > Sure. > > > I guess implementing the idea may be not so obvious; thus, seperating > > the patchset would be appropriate. > > > > When we implement the idea, we may need to implement at the > > pm_runtime core. Because devfreq->dev is a child of the target dev, not > > a parent, runtime-pm event of the target dev does not automatically > > invoke a cascaded action on the devfreq->dev. > > I'm not exactly sure what you mean, care to explain? When a device "p" creates devfreq, devfreq->dev->parent = p. And, devfreq's functions need to react to the "p"'s runtime-pm events. However, when "p"'s runtime-pm-suspend is being invoked, devfreq->dev's runtime-pm-suspend won't be automatically invoked. Thus, we will need a mechanism that invokes devfreq->dev's runtime-pm callbacks when p's runtime-pm is invoked. (at the runtime-pm core) Or A mechanism that one can notify others (including its children) when the one's runtime-pm is invoked. (probably at the runtime-pm core, too) Without such support, it appears that the current implementation (calling runtime-pm suspend/resume equivalent devfreq functions manually at device drivers) seems to be inevitable. Anyway, if devfreq->dev is a parent of "p", runtime-pm core will do the required task automatically; however, it isn't and I don't think it'd be appropriate. > > > Maybe either > > 1) capability to allow a child to monitor the power state of a parent > > (I remember Inki Dae once suggested to add notifiers at runtime-pm, but > > it seems to be not merged) > > or > > 2) letting runtime-pm be aware of devfreq > > (doesn't feel alright with this??) > > is required? > > I'm not a big fan of notifiers, so I'd prefer to avoid using them, if > possible. > > Thanks, > Rafael > > > -- > I speak only for myself. > Rafael J. Wysocki, Intel Open Source Technology Center. > Cheers, MyungJoo {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I