linux-kernel - Re: [PATCH v1 00/30] Introduce core voltage scaling for NVIDIA Tegra20/30 SoCs

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Date:   Thu, 5 Nov 2020 16:10:09 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Peter Chen <Peter.Chen@....com>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Lee Jones <lee.jones@...aro.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        driverdevel <devel@...verdev.osuosl.org>,
        Linux USB List <linux-usb@...r.kernel.org>,
        linux-pwm@...r.kernel.org,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v1 00/30] Introduce core voltage scaling for NVIDIA
 Tegra20/30 SoCs

On 05-11-20, 11:34, Ulf Hansson wrote:
> I am not objecting about scaling the voltage through a regulator,
> that's fine to me. However, encoding a power domain as a regulator
> (even if it may seem like a regulator) isn't. Well, unless Mark Brown
> has changed his mind about this.
>
> In this case, it seems like the regulator supply belongs in the
> description of the power domain provider.

Okay, I wasn't sure if it is a power domain or a regulator here. Btw,
how do we identify if it is a power domain or a regulator ?

> > In case of Qcom earlier (when we added the performance-state stuff),
> > the eventual hardware was out of kernel's control and we didn't wanted
> > (allowed) to model it as a virtual regulator just to pass the votes to
> > the RPM. And so we did what we did.
> >
> > But if the hardware (where the voltage is required to be changed) is
> > indeed a regulator and is modeled as one, then what Dmitry has done
> > looks okay. i.e. add a supply in the device's node and microvolt
> > property in the DT entries.
> 
> I guess I haven't paid enough attention how power domain regulators
> are being described then. I was under the impression that the CPUfreq
> case was a bit specific - and we had legacy bindings to stick with.
> 
> Can you point me to some other existing examples of where power domain
> regulators are specified as a regulator in each device's node?

No, I thought it is a regulator here and not a power domain.

-- 
viresh