From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751976AbeERQZc (ORCPT ); Fri, 18 May 2018 12:25:32 -0400 Received: from mail-pg0-f67.google.com ([74.125.83.67]:43807 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751117AbeERQZ2 (ORCPT ); Fri, 18 May 2018 12:25:28 -0400 X-Google-Smtp-Source: AB8JxZrgUCu9cMZ5+g3OKWHv012Th9ikmE1zZW2oVFXcbzwb40o5csJhFv8EpJhWDfkEcW5GfbS/Mw== Date: Fri, 18 May 2018 09:25:25 -0700 From: Matthias Kaehlcke To: Chanwoo Choi Cc: MyungJoo Ham , Kyungmin Park , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Brian Norris Subject: Re: [RFC PATCH] PM / devfreq: Add policy notifier Message-ID: <20180518162525.GA29467@google.com> References: <20180515212447.180595-1-mka@chromium.org> <5AFCE27E.20803@samsung.com> <20180517230728.GQ19594@google.com> <5AFE0FA6.4020101@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5AFE0FA6.4020101@samsung.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 18, 2018 at 08:26:30AM +0900, Chanwoo Choi wrote: > Hi, > > On 2018년 05월 18일 08:07, Matthias Kaehlcke wrote: > > Hi, > > > > On Thu, May 17, 2018 at 11:01:34AM +0900, Chanwoo Choi wrote: > >> Hi, > >> > >> Could you give some use-case of DEVFREQ_POLICY_NOTIFIER > >> or send use-case patch with this patch? > > > > This is a WIP patch that makes use of the DEVFREQ_POLICY_NOTIFIER: > > > > https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/1065122 > > > >> I already knew the CPUFREQ_POLICY_NOTIFIER. > >> But, until now, there are no any requirements of DEVFREQ_POLICY_NOTIFIER. > >> If there are no any use-case, it is not necessary codes. > > > > Sure, I intend to land the above driver upstream if devfreq can > > provide the necessary interfaces. > > I recommend that you should send the patch with the use-case patch. One of the reasons this patch was sent as an RFC was to get an idea whether it would be feasible to add support for DEVFREQ_POLICY_NOTIFIER before spending much time implementing a driver that relies on it, and then possibly hear that it's not going to fly. However since you didn't voice general concerns about the idea I made progress with the driver in the last days. I'll polish it a bit more and send it in a series with related devfreq patches. > >> On 2018년 05월 16일 06:24, Matthias Kaehlcke wrote: > >>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c > >>> index fe2af6aa88fc..a7294c056f65 100644 > >>> --- a/drivers/devfreq/devfreq.c > >>> +++ b/drivers/devfreq/devfreq.c > >>> @@ -273,6 +273,9 @@ int update_devfreq(struct devfreq *devfreq) > >>> if (err) > >>> return err; > >>> > >>> + srcu_notifier_call_chain(&devfreq->policy_notifier_list, > >>> + DEVFREQ_ADJUST, &freq); > >> > >> It is not proper to used 'freq' as the passed data. > >> In current step,'freq' is not adjusted and is not final decided > >> frequency. > > > > Right, the next revision will pass a struct devfreq_policy instead, > > where the notifiers can adjust the min/max values, similar to what > > cpufreq does. > > Actually, I don't know the devfreq_policy(?). As I already commented, > it is not proper to discuss it because there is no any real code and patches. > It is difficult to understand for me.