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Date:   Mon, 4 May 2020 18:40:27 +0200
From:   Maxime Ripard <maxime@cerno.tech>
To:     =?utf-8?B?Q2zDqW1lbnQgUMOpcm9u?= <peron.clem@gmail.com>
Cc:     Robin Murphy <robin.murphy@arm.com>, Chen-Yu Tsai <wens@csie.org>,
        Rob Herring <robh+dt@kernel.org>,
        devicetree <devicetree@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-sunxi <linux-sunxi@googlegroups.com>,
        Piotr Oniszczuk <warpme@o2.pl>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [linux-sunxi] Re: [PATCH v2] arm64: dts: allwinner: h6: Use
 dummy regulator for Tanix TX6
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Hi,

On Thu, Apr 30, 2020 at 03:48:04PM +0200, Cl=E9ment P=E9ron wrote:
> On Tue, 28 Apr 2020 at 18:45, Maxime Ripard <maxime@cerno.tech> wrote:
> >
> > On Tue, Apr 28, 2020 at 06:23:35PM +0200, Cl=E9ment P=E9ron wrote:
> > > Hi Robin,
> > >
> > > On Tue, 28 Apr 2020 at 17:21, Robin Murphy <robin.murphy@arm.com> wro=
te:
> > > >
> > > > On 2020-04-28 3:26 pm, Cl=E9ment P=E9ron wrote:
> > > > > Tanix TX6 has a fixed regulator. As DVFS is instructed to change
> > > > > voltage to meet OPP table, the DVFS is not working as expected.
> > > >
> > > > Hmm, isn't that really a bug in the DVFS code? I guess it's just bl=
indly
> > > > propagating -EINVAL from the fixed regulators not implementing
> > > > set_voltage, but AFAICS it has no real excuse not to be cleverer and
> > > > still allow switching frequency as long as the voltage *is* high en=
ough
> > > > for the given OPP. I wonder how well it works if the regulator is
> > > > programmable but shared with other consumers... that case probably =
can't
> > > > be hacked around in DT.
> > >
> > > Like you, I thought that the DVFS was clever enough to understand this
> > > but guess not..
> > >
> > > Maybe they are some cases where you don't want to leave the voltage h=
igh and
> > > reduce the frequency. But I don't know such case.
> >
> > I assume the intent was to prevent a regulator driver to overshoot and =
end up
> > over-volting the CPU which would be pretty bad.
> >
> > I guess we could check that the voltage is in the range opp < actual vo=
ltage <
> > max opp voltage ?
>=20
> As this could take more time than expected,
>=20
> Could you drop the commit :
> add1e27fb703f65f33191ccc70dd9d811254387c
> arm64: dts: allwinner: h6: Enable CPU opp tables for Tanix TX6

It's done, thanks!
Maxime

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