From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756616Ab1AaWo0 (ORCPT ); Mon, 31 Jan 2011 17:44:26 -0500 Received: from na3sys009aog101.obsmtp.com ([74.125.149.67]:41365 "EHLO na3sys009aog101.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754179Ab1AaWoZ (ORCPT ); Mon, 31 Jan 2011 17:44:25 -0500 From: Kevin Hilman To: Grant Likely Cc: "Rafael J. Wysocki" , Alan Stern , Magnus Damm , Linux-pm mailing list , Greg KH , LKML , Len Brown Subject: Re: [RFC][PATCH] Power domains for platform bus type Organization: Texas Instruments, Inc. References: <201101312316.52116.rjw@sisk.pl> <20110131222609.GC27856@angua.secretlab.ca> Date: Mon, 31 Jan 2011 14:44:19 -0800 In-Reply-To: <20110131222609.GC27856@angua.secretlab.ca> (Grant Likely's message of "Mon, 31 Jan 2011 15:26:09 -0700") Message-ID: <87vd1466d8.fsf@ti.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Grant Likely writes: > On Mon, Jan 31, 2011 at 11:16:51PM +0100, Rafael J. Wysocki wrote: >> On Monday, January 31, 2011, Alan Stern wrote: >> > On Mon, 31 Jan 2011, Rafael J. Wysocki wrote: >> > >> > > On Monday, January 31, 2011, Alan Stern wrote: >> > > > On Sun, 30 Jan 2011, Rafael J. Wysocki wrote: >> > > > >> > > > > > One thing about this implementation is slightly questionable. The new >> > > > > > power_domain callbacks were added to the __weak platform PM routines, >> > > > > > which means they will have to be included in every overriding routine >> > > > > > provided by a platform imiplementation. >> > > > > > >> > > > > > Would it be better to separate these things? Have the power_domain >> > > > > > callbacks occur in a static outer function which then calls a public >> > > > > > __weak inner function that can be overridden? >> > > > > >> > > > > That certainly is a good idea, but I wasn't sure how to do that. It looks >> > > > > like I could keep the __weak functions as they are and modify >> > > > > platform_dev_pm_ops instead to point to a new set of function that in turn >> > > > > would call the __weak ones. For example, the .suspend pointer in >> > > > > platform_dev_pm_ops might point to a new function, say >> > > > > platform_pm_full_suspend() that would call the power domain functions and >> > > > > the "original" platform_pm_suspend(). Is that what you mean? >> > > > >> > > > Yes. But what about the platform_bus_set_pm_ops() interface? Should >> > > > platform-specific replacements for the pm_ops functions also include >> > > > the power_domain callbacks? >> > > >> > > Well, whoever uses platform_bus_set_pm_ops(), he can simply prevent power >> > > domains from being used by not defining them in the first place. :-) >> > >> > But what about the case where the user _does_ want to have power >> > domains? >> >> Ah, OK. The caller of platform_bus_set_pm_ops() will replace the original >> platform_dev_pm_ops with his own set of operations, so he will not see the >> power domains. >> >> > Do you want to make the replacement routines responsible for >> > invoking the power-domain callbacks, or should the platform core handle >> > this automatically? >> >> Well, if someone replaces the entire platform_dev_pm_ops object, this means >> that on his platform power management is substantially different from the >> generic one. In that case, IMO, he should be responsible for handling all >> of the subsystem-level aspects of power management, including power domains. > > Part of point of doing something like power_domain is to *get rid* of > platform_bus_set_pm_ops(). It is a horrid, stop-gap interface that > doesn't scale. I don't think much consideration needs to be made for > users of platform_bus_set_pm_ops() in this regard. As the author of platform_bus_set_pm_ops(), I humbly agree. Also, the __weak functions here were obsoleted by platform_bus_set_pm_ops(). Once Magnus moves to platform_bus_set_pm_ops() (or this new interface) the __weak attributes should be removed (c.f. commit log below[1] where platform_bus_set_pm_ops() was added.) Kevin commit c64a0926710153b9d44c979d2942f4a8648fd74e Author: Kevin Hilman Date: Wed Aug 25 12:50:00 2010 -0700 driver core: platform_bus: allow runtime override of dev_pm_ops Currently, the platform_bus allows customization of several of the busses dev_pm_ops methods by using weak symbols so that platform code can override them. The weak-symbol approach is not scalable when wanting to support multiple platforms in a single kernel binary. Instead, provide __init methods for platform code to customize the dev_pm_ops methods at runtime. NOTE: after these dynamic methods are merged, the weak symbols should be removed from drivers/base/platform.c. AFAIK, this will only affect SH and sh-mobile which should be converted to use this runtime approach instead of the weak symbols. After SH & sh-mobile are converted, the weak symobols could be removed.