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

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Message-ID: <20201105100603.skrirm7uke4s2xyl@vireshk-i7>
Date:   Thu, 5 Nov 2020 15:36:03 +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, 10:45, Ulf Hansson wrote:
> + Viresh

Thanks Ulf. I found a bug in OPP core because you cc'd me here :)

> On Thu, 5 Nov 2020 at 00:44, Dmitry Osipenko <digetx@...il.com> wrote:
> I need some more time to review this, but just a quick check found a
> few potential issues...
> 
> The "core-supply", that you specify as a regulator for each
> controller's device node, is not the way we describe power domains.

Maybe I misunderstood your comment here, but there are two ways of
scaling the voltage of a device depending on if it is a regulator (and
can be modeled as one in the kernel) or a power domain.

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.

-- 
viresh