From mboxrd@z Thu Jan 1 00:00:00 1970 From: Niklas Cassel Subject: Re: [PATCH v4 2/6] dt-bindings: power: Add qcom rpm power domain driver bindings Date: Thu, 4 Oct 2018 21:17:25 +0200 Message-ID: <20181004191725.GA7926@centauri.lan> References: <20180627045234.27403-1-rnayak@codeaurora.org> <20180627045234.27403-3-rnayak@codeaurora.org> <20180703223554.GA32313@rob-hp-laptop> <20180704055757.4li26b6poxllmh2k@vireshk-i7> <1463d24b-481d-eecd-9e44-e7a5a993e5fc@codeaurora.org> <271db7b1-f65b-f42d-b00b-9362429b3749@codeaurora.org> <20181004083637.xlz26rpn4qtsvdk7@vireshk-i7> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Rob Herring Cc: Viresh Kumar , Rajendra Nayak , Stephen Boyd , Andy Gross , Ulf Hansson , David Collins , Matthias Kaehlcke , devicetree@vger.kernel.org, linux-arm-msm , "linux-kernel@vger.kernel.org" List-Id: linux-arm-msm@vger.kernel.org On Thu, Oct 04, 2018 at 10:18:22AM -0500, Rob Herring wrote: > On Thu, Oct 4, 2018 at 3:36 AM Viresh Kumar wrote: > > > > On 25-09-18, 14:43, Rob Herring wrote: > > > On Tue, Sep 25, 2018 at 5:25 AM Rajendra Nayak wrote: > > > > > > > > Hi Rob, > > > > > > > > []... > > > > >>>>> + rpmhpd_opp_table: opp-table { > > > > >>>>> + compatible = "operating-points-v2-qcom-level"; > > > > >>>>> + > > > > >>>>> + rpmhpd_opp_ret: opp1 { > > > > >>>>> + qcom,level = ; > > > > >>>>> + }; > > > > >>>> > > > > >>>> I don't see the point in using the OPP binding here when you aren't > > > > >>>> using *any* of the properties from it. > > > > >>> > > > > >>> Yeah, that's the case for now. But there are cases (as Stephen > > > > >>> mentioned earlier [1]) where the voltage values (and maybe other > > > > >>> values like current, etc) would be known and filled in DT. And that's > > > > >>> why we all agreed to use OPP tables for PM domains as well, as these > > > > >>> are really "operating performance points" of these PM domains. > > > > >> > > > > >> Rob, are you fine with these bindings then? > > > > > > > > > > Okay, my only thought is whether we should just use 'reg' here, or do > > > > > we need 'level' for anything else and should make it common? > > > > > > > > I am not quite sure I understood what you are suggesting here :( > > > > > > You could use the 'reg' property instead of 'qcom,level'. Any reason > > > not to do that? > > > > They can use any property which uniquely identifies the OPP nodes in > > the table. Though I never thought we can use 'reg' property in such a > > way. I always thought it must be related to registers somehow :) > > That's almost certainly where the name originates from back in the > 90s. I view 'reg' as how you identify or address a device. This can be > channels of something like an ADC. > > It's perhaps a stretch for OPP nodes as they aren't really a device, > but if the levels are part of the h/w then perhaps reg is a good > match. > FWIW, I actually have a use case on qcom SoCs. I'm working on reviving an old patch series from Stephen Boyd: https://lkml.org/lkml/2015/9/18/833 Rajendra's Documentation/devicetree/bindings/opp/qcom-opp.txt currently has: Required properties: - qcom,level: On Qualcomm platforms an OPP node can describe a positive value representing a corner/level that's communicated with a remote microprocessor (usually called the RPM) which then translates it into a certain voltage on a voltage rail I'm planning on extending it with something like: Optional properties: -qcom,fuse-level: On Qualcomm platforms, not all corners/levels are real corners/levels, i.e., not all corners/levels have a unique eFuse associated. Usually more than one corner/level uses the same eFuse corner/level. So for each OPP I would have: opp1 { qcom,level = ; qcom,fuse-level = ; } Not sure if this changes your opinion about using reg, but I thought that it was worth mentioning. Kind regards, Niklas