From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751478AbdGNHBp (ORCPT <rfc822;w@1wt.eu>);
        Fri, 14 Jul 2017 03:01:45 -0400
Received: from isilmar-4.linta.de ([136.243.71.142]:60670 "EHLO
        isilmar-4.linta.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1750853AbdGNHBo (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 14 Jul 2017 03:01:44 -0400
Date: Fri, 14 Jul 2017 09:01:42 +0200
From: Dominik Brodowski <linux@dominikbrodowski.net>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>,
        Rafael Wysocki <rjw@rjwysocki.net>,
        Linux PM <linux-pm@vger.kernel.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RFC V2 1/6] cpufreq: Replace "max_transition_latency" with
 "dynamic_switching"
Message-ID: <20170714070142.GA14515@isilmar-4.linta.de>
References: <cover.1499853492.git.viresh.kumar@linaro.org>
 <4b9ff9a3f546b2269ddb2da27c9e5be5f106a70f.1499853492.git.viresh.kumar@linaro.org>
 <CAJZ5v0g-DgV6G-J9pkAYKooqgbJDV_ML8cR8wquKksN=x_JpoQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAJZ5v0g-DgV6G-J9pkAYKooqgbJDV_ML8cR8wquKksN=x_JpoQ@mail.gmail.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, Jul 13, 2017 at 06:19:53PM +0200, Rafael J. Wysocki wrote:
> On Thu, Jul 13, 2017 at 7:40 AM, Viresh Kumar <viresh.kumar@linaro.org> wrote:
> > There is no limitation in the ondemand or conservative governors which
> > disallow the transition_latency to be greater than 10 ms.
> >
> > The max_transition_latency field is rather used to disallow automatic
> > dynamic frequency switching for platforms which didn't wanted these
> > governors to run.
> >
> > Replace max_transition_latency with a boolean (dynamic_switching) and
> > check for transition_latency == CPUFREQ_ETERNAL along with that. This
> > makes it pretty straight forward to read/understand now.
> 
> Well, using CPUFREQ_ETERNAL for that on the driver side is still not
> particularly straightforward IMO, so maybe add a
> "no_dynamic_switching" to the driver structure and set it to "true"
> for the one driver in question?

IIRC it's not just one driver which sets the latency to CPUFREQ_ETERNAL, and
where dynamic switching might be harmful or at least lead to undefined
behavior.

Best,
	Dominik