Re: [PATCH v5 09/18] arm64: dts: qcom: qrb5165-rb5: model the PMU of the QCA6391

From: Bartosz Golaszewski <brgl@bgdev.pl>
To: Mark Brown <broonie@kernel.org>
Cc: Marcel Holtmann <marcel@holtmann.org>,
	Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
	 "David S . Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	 Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>, Rob Herring <robh@kernel.org>,
	 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	 Kalle Valo <kvalo@kernel.org>,
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	 Konrad Dybcio <konrad.dybcio@linaro.org>,
	Liam Girdwood <lgirdwood@gmail.com>,
	 Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
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	Lukas Wunner <lukas@wunner.de>,
	 Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
	linux-bluetooth@vger.kernel.org,  netdev@vger.kernel.org,
	devicetree@vger.kernel.org,  linux-kernel@vger.kernel.org,
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	linux-arm-kernel@lists.infradead.org,  linux-pci@vger.kernel.org,
	linux-pm@vger.kernel.org,
	 Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Subject: Re: [PATCH v5 09/18] arm64: dts: qcom: qrb5165-rb5: model the PMU of the QCA6391
Date: Tue, 20 Feb 2024 12:16:10 +0100	[thread overview]
Message-ID: <CAMRc=MeAXEyV47nDO_WPQqEQxSYFWTrwVPAtLghkfONj56FGVA@mail.gmail.com> (raw)
In-Reply-To: <8e392aed-b5f7-486b-b5c0-5568e13796ec@sirena.org.uk>

On Mon, Feb 19, 2024 at 8:59 PM Mark Brown <broonie@kernel.org> wrote:
>
> On Mon, Feb 19, 2024 at 07:48:20PM +0100, Bartosz Golaszewski wrote:
> > On Mon, Feb 19, 2024 at 7:03 PM Mark Brown <broonie@kernel.org> wrote:
> > > On Fri, Feb 16, 2024 at 09:32:06PM +0100, Bartosz Golaszewski wrote:
>
> > > > +                     vreg_pmu_aon_0p59: ldo1 {
> > > > +                             regulator-name = "vreg_pmu_aon_0p59";
> > > > +                             regulator-min-microvolt = <540000>;
> > > > +                             regulator-max-microvolt = <840000>;
> > > > +                     };
>
> > > That's a *very* wide voltage range for a supply that's got a name ending

Because it's an error, it should have been 640000. Thanks for spotting it.

> > > in _0_p59 which sounds a lot like it should be fixed at 0.59V.
> > > Similarly for a bunch of the other supplies, and I'm not seeing any
> > > evidence that the consumers do any voltage changes here?  There doesn't
> > > appear to be any logic here, I'm not convinced these are validated or
> > > safe constraints.
>
> > No, the users don't request any regulators (or rather: software
> > representations thereof) because - as per the cover letter - no
> > regulators are created by the PMU driver. This is what is physically
> > on the board - as the schematics and the datasheet define it. I took
>
> The above makes no sense.  How can constraints be "what is physically on
> the board", particularly variable constrants when there isn't even a
> consumer?  What values are you taking from which documentation?
>

The operating conditions for PMU outputs. I took them from a
confidential datasheet. There's a table for input constraints and
possible output values.

And what do you mean by there not being any consumers? The WLAN and BT
*are* the consumers.

> The cover letter and binding both claimed (buried after large amounts of
> changelog) that these PMUs were exposing regulators to consumers and the
> DTS puports to do exactly that...
>

Yes, but I'm not sure what the question is.

> > the values from the docs verbatim. In C, we create a power sequencing
> > provider which doesn't use the regulator framework at all.
>
> For something that doesn't use the regulator framework at all what
> appears to be a provider in patch 16 ("power: pwrseq: add a driver for
> the QCA6390 PMU module") seems to have a lot of regualtor API calls?

This driver is a power sequencing *provider* but also a regulator
*consumer*. It gets regulators from the host and exposes a power
sequencer to *its* consumers (WLAN and BT). On DT it exposes
regulators (LDO outputs of the PMU) but we don't instantiate them in
C.

Bart