From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from arroyo.ext.ti.com ([192.94.94.40]:44637 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751701Ab3HFNaD (ORCPT ); Tue, 6 Aug 2013 09:30:03 -0400 Date: Tue, 6 Aug 2013 08:29:57 -0500 From: Nishanth Menon Subject: Re: [RFC PATCH 1/2] PM / OPP: add support to specify phandle of another node for OPP Message-ID: <20130806132956.GA6603@kahuna> References: <51F826A0.2000109@ti.com> <51F8F17B.1020304@arm.com> <51F9234A.6010501@ti.com> <20130731152925.GP29859@e106331-lin.cambridge.arm.com> <51F9341E.60102@ti.com> <20130731161103.GS29859@e106331-lin.cambridge.arm.com> <51F93AFB.1030104@ti.com> <20130801135422.GA8095@e106331-lin.cambridge.arm.com> <51FA917D.4060408@wwwdotorg.org> <51FBB788.7040209@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <51FBB788.7040209@arm.com> Sender: devicetree-owner@vger.kernel.org To: Sudeep KarkadaNagesha Cc: Stephen Warren , Mark Rutland , "cpufreq@vger.kernel.org" , "linux-pm@vger.kernel.org" , "devicetree@vger.kernel.org" , "rob.herring@calxeda.com" , Pawel Moll , "Rafael J. Wysocki" List-ID: On 14:43-20130802, Sudeep KarkadaNagesha wrote: > On 01/08/13 17:49, Stephen Warren wrote: > > On 08/01/2013 07:54 AM, Mark Rutland wrote: > > ... > >> We seem to be going over two cases, which both feel wrong to me: > >> > >> * One SoC used in multiple boards, where on some boards an OPP cannot be > >> used because some requirement is not met. In this case, the board's > >> dts (by including the SoC's dtsi) describes something that's not > >> necessarily usable, and we seem to have no way to describe in the OPP > >> table that the OPP is not usable for that board. > > > > There are probably a lot of examples of this already. For example, for > > pinctrl, people often want the SoC .dtsi file to include "pin > > configuration nodes" (see > > Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt) for many > > common pinmux configurations in the SoC .dtsi file, so that board files > > can simply refer to the already-existing nodes rather than having to > > write everything from scratch. Obviously, not all common configurations > > are used by every board. > > > > ... > Agreed, but I am not convinced with the comparison(pinmux and OPPs). > The main concern I have is that if some developer wants to experiment > with various configurations provided by SoC(e.g. I have seen some SoC > where the pinmux have multiple functions and you can chose one of them) > But that's not true with OPPs, if someone experiments with wrong OPP > profile, then it might damage the board permanently. Even today, nothing prevents folks from "adding custom OPPs" at their own personal risk here - We have seen folks do this as part of board files - Now, for that matter, there is nothing that prevents folks linking the wrong LDO or setting wrong LDO voltage and damaging the board either. I mean, at the level where we "describe" the hardware and it's operation, you cannot be idiot or experimenter-proof - If these were to be considered paramount and prevent us from choosing the right concept that is needed for as many SoCs as possible, it'd be a shame. -- Regards, Nishanth Menon