From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754582AbbAWNr2 (ORCPT ); Fri, 23 Jan 2015 08:47:28 -0500 Received: from mout.kundenserver.de ([212.227.126.131]:57112 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754067AbbAWNr0 (ORCPT ); Fri, 23 Jan 2015 08:47:26 -0500 From: Arnd Bergmann To: Geert Uytterhoeven Cc: Kevin Hilman , Geert Uytterhoeven , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Grant Likely , Ulf Hansson , "Rafael J. Wysocki" , Olof Johansson , Simon Horman , Magnus Damm , Greg Kroah-Hartman , "devicetree@vger.kernel.org" , Linux-sh list , Linux PM list , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v3/resend 3/4] drivers: bus: Add Simple Power-Managed Bus DT Bindings Date: Fri, 23 Jan 2015 14:46:35 +0100 Message-ID: <2160255.41m7rrCYxI@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: References: <1421919253-4784-1-git-send-email-geert+renesas@glider.be> <7hvbjy30an.fsf@deeprootsystems.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:2kpG32yHO4iNec4M/MGLS/TRIwpSt551n72cVyPAl722VA8ePQA 0vAD7tkjpA0xV3wpnNcxSzkLpjRJ2bgTolG33oHW7aFMK/7Sc2rNkJCTx628Q9Hs6iDxwWA ojebHnWqv2G4SO6kNfHfSoGndAGMDosRVF3KfZpczARI2VwDZUlCKcrZpMMbM9uxk49diRd 5HSbNTiYpuUFSsaRNvOvg== X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday 23 January 2015 09:56:51 Geert Uytterhoeven wrote: > >> diff --git a/Documentation/devicetree/bindings/bus/simple-pm-bus.txt b/Documentation/devicetree/bindings/bus/simple-pm-bus.txt > >> new file mode 100644 > >> index 0000000000000000..d03abf7fd8e3997a > >> --- /dev/null > >> +++ b/Documentation/devicetree/bindings/bus/simple-pm-bus.txt > >> @@ -0,0 +1,52 @@ > >> +Simple Power-Managed Bus > >> +======================== > >> + > >> +A Simple Power-Managed Bus is a transparent bus that doesn't need a real > >> +driver, as it's typically initialized by the boot loader. > >> + > >> +However, its bus controller is part of a PM domain, or under the control of a > >> +functional clock. Hence, the bus controller's PM domain and/or clock must be > >> +enabled for child devices connected to the bus (either on-SoC or externally) > >> +to function. > >> + > >> + > >> +Generic compatible values and properties > >> +---------------------------------------- > >> + > >> +Required properties: > >> + - compatible: Must be at least one of the vendor-specific compatible values > >> + from a vendor-specific section below, and "simple-bus" as a > >> + fallback. > > > > What happened to the idea of using something like "simple-pm-bus"? > > I think that's a decision to make by the (successor of the) ePAPR committee. > At least it would be nice to get some feedback from the DT review team > about this. > > If we go that road, the vendor-specific compatible value should still be > documented, else checkpatch will complain when encountering it in a DTS. > Then, should it become > > compatible = "renesas,bsc-sh73a0", "renesas,bsc", "simple-pm-bus", > "simple-bus"; > > or should "simple-bus" just be added to of_default_bus_match_table[], so we > can drop "simple-bus" from the list in the DTS: > > compatible = "renesas,bsc-sh73a0", "renesas,bsc", "simple-pm-bus"; I was thinking of the reverse: drop "simple-bus" bus from the list here, but not add "simple-pm-bus" to of_default_bus_match_table. This will cause child devices to no longer be probed automatically, and you will have to call of_platform_populate() from simple_pm_bus_probe(), after pm_runtime_enable(). This seems like a cleaner model to me, for two reasons: - In the binding, claiming compatibility with "simple-bus" feels wrong to me, because you have a bus that is not as simple as others - The ordering between pm_runtime_enable() and the probing of the child devices is guaranteed, which I think it is not with your current code. Does this make sense, or am I missing an important reason why there has to be a "simple-bus" compatible string here? Arnd