Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751654AbaKUTUL (ORCPT ); Fri, 21 Nov 2014 14:20:11 -0500 Received: from mail-pa0-f53.google.com ([209.85.220.53]:35410 "EHLO mail-pa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750871AbaKUTUJ (ORCPT ); Fri, 21 Nov 2014 14:20:09 -0500 From: Kevin Hilman To: Geert Uytterhoeven Cc: Grygorii Strashko , Ulf Hansson , Arnd Bergmann , ssantosh@kernel.org, "Rafael J. Wysocki" , "linux-pm\@vger.kernel.org" , Rob Herring , Grant Likely , "linux-arm-kernel\@lists.infradead.org" , "linux-kernel\@vger.kernel.org" , "devicetree\@vger.kernel.org" , Dmitry Torokhov Subject: Re: [PATCH v4 1/2] ARM: keystone: pm: switch to use generic pm domains References: <1415631557-22897-1-git-send-email-grygorii.strashko@ti.com> <1709760.E0jX3Myv0h@wuerfel> <546C7FDD.7030906@ti.com> <2900095.WIocOu7ue2@wuerfel> <546DD87B.3080806@ti.com> <546E0970.5090301@ti.com> <7hh9xtr5ac.fsf@deeprootsystems.com> <7hbno1r1af.fsf@deeprootsystems.com> <7hppchpcfm.fsf@deeprootsystems.com> Date: Fri, 21 Nov 2014 11:20:05 -0800 In-Reply-To: (Geert Uytterhoeven's message of "Fri, 21 Nov 2014 09:06:09 +0100") Message-ID: <7h8uj4nyxm.fsf@deeprootsystems.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Geert Uytterhoeven writes: > Hi Kevin, > > On Fri, Nov 21, 2014 at 2:30 AM, Kevin Hilman wrote: >> Geert Uytterhoeven writes: >>> On Thu, Nov 20, 2014 at 10:48 PM, Kevin Hilman wrote: >>>>>> So what exactly are we talking about with "PM" clocks, and why are they >>>>>> "special" when it comes to PM domains? IOW, why are the clocks to be >>>>>> managed during PM domain transitions for a given device any different >>>>>> than the clocks that need to be managed for a runtime suspend/resume (or >>>>>> system suspend/resume) sequence for the same device? >>>>> >>>>> (Speaking for my case, shmobile) >>>>> >>>>> They're not. The clocks to be managed during PM domain transitions are the >>>>> same as the clocks that need to be managed for a runtime suspend/resume >>>>> (or system suspend/resume) sequence. >>>>> >>>>> The special thing is that this is more a platform than a driver thing: the same >>>>> module may have a "PM/functional" clock (that is documented to enable/disable >>>>> the module) on one Soc, but noet on another. >>>> >>>> So why isn't the presence or absence of the clock described in the .dtsi >>>> for the SoC instead of being handled by special PM domain logic? >>> >>> It is. Cfr. the presence/absence of clocks for renesas,rcar-gpio nodes. >> >> Hmm, OK, Good. >> >> So now I'm confused about why the PM domain has to do anything special >> if the presence/absence of the clocks is already handled by the DT. > > Just adding a clock property to a device node in DT doesn't enable the clock > automatically, nor make it runtime-managed automatically. In general, that's true. But I thought you're PM domain was written to look for clock properties, and if present would manage them. The proposed genpd support for TI Keystone2 would make it so these clocks would definitely be automatically managed by the PM domain. > Compare this to e.g. pinctrl, where adding pinctrl properties to DT does enable > them automatically, without the driver for the device having to care about it. Well, we're headed down the same path with genpd (if given the right properties in genpd.) > Drivers interfacing external hardware typically do care about clocks, as they > have to program clock generators for the external hardware interface (e.g. > driving spi or i2c buses at specific frequencies). Yes, but IMO, these should be handled by the driver, not by the PM domain. More specifically, if a device is generating a clock for external hardware, presumably it cannot be runtime suspended, so the enclosing PM domain can be powered off. If it's not generating a clock, then it can be runtime suspended and presumably would gate it's externally facing clocks when it runtime suspends. > Other random drivers don't care about clocks, so they don't handle them. > But as long as they make basic pm_runtime_{enable,get_sync,put}() calls, > the (optional) clocks (and hardware PM domains) will "work" fine, if handled > by the PM (clock) domain. Yes, I understand that. But this still isn't helping me understand why your PM domain has to distinguish between different types of clocks (e.g. why it only manages the first clock.) Did you set up the properties so that the first clock was the functional clock and any additional ones were for devices that generate external clocks? Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/