Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752141AbaLCTbD (ORCPT ); Wed, 3 Dec 2014 14:31:03 -0500 Received: from mail-pd0-f177.google.com ([209.85.192.177]:53506 "EHLO mail-pd0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750855AbaLCTa7 (ORCPT ); Wed, 3 Dec 2014 14:30:59 -0500 From: Kevin Hilman To: Geert Uytterhoeven Cc: Arnd Bergmann , Geert Uytterhoeven , Laurent Pinchart , Ulrich Hecht , Simon Horman , Magnus Damm , "Rafael J. Wysocki" , Ulf Hansson , Grant Likely , Greg Kroah-Hartman , Linux PM list , "devicetree\@vger.kernel.org" , Linux-sh list , "linux-kernel\@vger.kernel.org" Subject: Re: [PATCH RFC 0/3] Add "Simple" / Renesas Bus State Controller Driver References: <1416859808-18503-1-git-send-email-geert+renesas@glider.be> <6261300.I132f1jLqB@wuerfel> <7h4mtlen8f.fsf@deeprootsystems.com> Date: Wed, 03 Dec 2014 11:30:55 -0800 In-Reply-To: (Geert Uytterhoeven's message of "Wed, 3 Dec 2014 10:30:06 +0100") Message-ID: <7hbnnkzg28.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, Arnd, > > I've been giving this some more thoughts... > > On Wed, Nov 26, 2014 at 9:11 PM, Kevin Hilman wrote: >> Geert Uytterhoeven writes: >>> On Mon, Nov 24, 2014 at 9:15 PM, Arnd Bergmann wrote: >>>> On Monday 24 November 2014 21:10:05 Geert Uytterhoeven wrote: >>>>> As this minimal BSC driver isn't hardware-specific at all, I'm wondering >>>>> if there's a simpler way to do this? >>>>> - Should the driver be renamed to "simple-bus", and match "simple-bus"? >>>>> - Should this be moved to core code, without an explicit driver for >>>>> "simple-bus"? I.e. should the driver core just enable runtime PM for >>>>> all devices not bound to a driver, as they may represent buses with >>>>> child devices that do rely on runtime PM? >>>>> >>>>> Thanks for your comments and suggestions! >>>> >>>> My understanding of simple-bus is that it's something that does >>>> not have any power-management capabilities, and I'd rather not >>>> add clocks or interrupts to it. > > Should I not add the interrupt to the device node, even though I do > know the hardware block has an interrupt? > Of course, to make use of the interrupt, you do need a hardware-specific > driver that binds to the specific compatible name. But for now such a > driver is overkill, as I do not need to use the interrupt. > > Power domains (and clocks used for power management) are different, > as they are platform features: they may appear in any device node, even if > the bindings for the device node don't mention them. > Else I cannot add them to a node that's compatible with e.g. "arm,cortex-a15" > or "arm,pl310-cache", without adding (or completely replacing them with) > compatible names like "renesas,r8a73a4-cortex-a15" resp. > "renesas,sh73a0-pl310-cache"? > Hence I think they should be allowed in "simple-bus" nodes, too. > >>>> What I think makes more sense is to have a bus driver for it >>>> in drivers/bus, remove the "simple-bus" compatibility value >>>> and have the driver take care of registering the power domain >>>> and probing the child devices using of_platform_populate on >>>> itself. >>> >>> Registering power domains is already handled by the core code. >>> >>> So compared to my RFC code, I only have to >>> 1. Drop "simple-bus" from the compatible property in the .dtsi, >>> 2. Call of_platform_populate() from renesas_bsc_probe(), to >>> register the child devices, now the core code no longer does that. >>> >>> I find it a bit strange having to add _more_ code, as the core code handles >>> registering child devices fine. Doing it from my bus driver only protects >>> against people trying to run a kernel without my bus driver included >>> (which currently works fine, as long as no PM domain or clock is involved, >>> e.g. if the clock is forgotten in the SoC's .dtsi :-). >> >> I actually rather like the simple bus driver in it's current form, where >> the device and pm-domain registration is taken care of by the >> core. Since it's really not HW specific at all, maybe just rename it >> simple-pm-bus or something like that? > > That means writing bindings for a new bus type "simple-pm-bus"? Well, I'm OK with adding common properties to simple-bus also, but presuably you'll want to document those as well in a binding doc for simple-bus. 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/