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

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Message-ID: <CAMRc=MeAXEyV47nDO_WPQqEQxSYFWTrwVPAtLghkfONj56FGVA@mail.gmail.com>
Date: Tue, 20 Feb 2024 12:16:10 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Mark Brown <broonie@...nel.org>
Cc: Marcel Holtmann <marcel@...tmann.org>, Luiz Augusto von Dentz <luiz.dentz@...il.com>, 
	"David S . Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Kalle Valo <kvalo@...nel.org>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, Liam Girdwood <lgirdwood@...il.com>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Saravana Kannan <saravanak@...gle.com>, 
	Geert Uytterhoeven <geert+renesas@...der.be>, Arnd Bergmann <arnd@...db.de>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Marek Szyprowski <m.szyprowski@...sung.com>, 
	Alex Elder <elder@...aro.org>, Srini Kandagatla <srinivas.kandagatla@...aro.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Abel Vesa <abel.vesa@...aro.org>, 
	Manivannan Sadhasivam <mani@...nel.org>, Lukas Wunner <lukas@...ner.de>, 
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, linux-bluetooth@...r.kernel.org, 
	netdev@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-pci@...r.kernel.org, linux-pm@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v5 09/18] arm64: dts: qcom: qrb5165-rb5: model the PMU of
 the QCA6391

On Mon, Feb 19, 2024 at 8:59 PM Mark Brown <broonie@...nel.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@...nel.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