From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brownell Subject: Re: Alternative Concept Date: Sun, 18 Mar 2007 21:04:26 -0700 Message-ID: <200703182104.27555.david-b@pacbell.net> References: <44ECFF94.3030506@gmail.com> <200703161103.12333.david-b@pacbell.net> <45FDA040.4020502@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <45FDA040.4020502@gmail.com> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: Dmitry Krivoschekov Cc: Dominik Brodowski , Pavel Machek , linux-pm@lists.osdl.org List-Id: linux-pm@vger.kernel.org On Sunday 18 March 2007 1:25 pm, Dmitry Krivoschekov wrote: > = > For me, there is a point that seems debatable already at the starting sta= ge: > = > > The goal of this parameter framework is to expose the resources in a = > > way that allows other s/w (governors, policy mangers, etc) to control = > > the resources while keeping the system operational. One of the main = > > requirements in our thinking is that we want this layer to represent = > > the h/w and not include policy or decision making. Meaning the = > > software using the parameter framework would be responsible for = > > deciding the appropriate value for the parameters. = > = > = > Sometimes it's quite reasonable to make decisions (or policy) > at the low level, without exposing events to higher layers, Of course. Any layer can incorporate a degree of policy. It's only when that's badly done -- or the problem is so complex that multiple policies need to be supported -- that you need to pull out that old "mechanism not policy" chestnut, and support some kind of policy switching mechanism (governors, userspace agents, etc) for different application domains. > e.g. turning a clock off when reference counter gets zero, this is > what OMAP's clock framework currently does. There are no choices to be made in that layer; it's no more "policy" than following the laws of arithmetic is "policy". Software clock gating is what the clock framework is defined as doing; there's nothing OMAP-specific about that. The interesting bit for OMAP is that clock gating will often be done in hardware, not just in software. There are other low-power SOC designs that do such things, but the ones I'm most aware of are for microcontrollers (MSP430, picoAVR, etc) that can't run Linux. - Dave