From: Maxime Ripard <maxime@cerno.tech>
To: "Clément Péron" <peron.clem@gmail.com>
Cc: devicetree <devicetree@vger.kernel.org>,
linux-sunxi <linux-sunxi@googlegroups.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Chen-Yu Tsai <wens@csie.org>, Rob Herring <robh+dt@kernel.org>,
Piotr Oniszczuk <warpme@o2.pl>,
Robin Murphy <robin.murphy@arm.com>,
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
Date: Tue, 28 Apr 2020 18:45:22 +0200 [thread overview]
Message-ID: <20200428164522.p7ypca7zwocc7alq@gilmour.lan> (raw)
In-Reply-To: <CAJiuCcco0d_UoWeHqh6oc0rFNAMFynXjLRQ6APsT0WBh7m+GQg@mail.gmail.com>
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On Tue, Apr 28, 2020 at 06:23:35PM +0200, Clément Péron wrote:
> Hi Robin,
>
> On Tue, 28 Apr 2020 at 17:21, Robin Murphy <robin.murphy@arm.com> wrote:
> >
> > On 2020-04-28 3:26 pm, Clément Péron 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 blindly
> > 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 enough
> > 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 high 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 voltage <
max opp voltage ?
Maxime
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next prev parent reply other threads:[~2020-04-28 16:45 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-28 14:26 [PATCH v2] arm64: dts: allwinner: h6: Use dummy regulator for Tanix TX6 Clément Péron
2020-04-28 14:30 ` Clément Péron
2020-04-28 15:21 ` Robin Murphy
2020-04-28 16:23 ` [linux-sunxi] " Clément Péron
2020-04-28 16:45 ` Maxime Ripard [this message]
2020-04-30 13:48 ` Clément Péron
2020-05-04 16:40 ` Maxime Ripard
2020-05-04 12:27 ` [linux-sunxi] " Ondřej Jirman
2020-05-04 19:34 ` Clément Péron
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