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

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Message-ID: <20201109051202.e4lkosy6kk334akq@vireshk-i7>
Date:   Mon, 9 Nov 2020 10:42:02 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        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 09-11-20, 08:10, Dmitry Osipenko wrote:
> 09.11.2020 07:47, Dmitry Osipenko пишет:
> > 09.11.2020 07:43, Viresh Kumar пишет:
> >> On 08-11-20, 15:19, Dmitry Osipenko wrote:
> >>> I took a detailed look at the GENPD and tried to implement it. Here is
> >>> what was found:
> >>>
> >>> 1. GENPD framework doesn't aggregate performance requests from the
> >>> attached devices. This means that if deviceA requests performance state
> >>> 10 and then deviceB requests state 3, then framework will set domain's
> >>> state to 3 instead of 10.
> >>
> >> It does. Look at _genpd_reeval_performance_state().
> >>
> > 
> > Thanks, I probably had a bug in the quick prototype and then overlooked
> > that function.
> > 
> 
> If a non-hardware device-tree node is okay to have for the domain, then
> I can try again.
> 
> What I also haven't mentioned is that GENPD adds some extra complexity
> to some drivers (3d, video decoder) because we will need to handle both
> new GENPD and legacy Tegra specific pre-genpd era domains.
> 
> I'm also not exactly sure how the topology of domains should look like
> because Tegra has a power-controller (PMC) which manages power rail of a
> few hardware units. Perhaps it should be
> 
>   device -> PMC domain -> CORE domain
> 
> but not exactly sure for now.

I am also confused on if it should be a domain or regulator, but that
is for Ulf to tell :)

-- 
viresh