linux-kernel - Re: [PATCH 0/9] PCI: introduce the concept of power sequencing of PCIe devices

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Date: Fri, 19 Jan 2024 15:48:24 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Kalle Valo <kvalo@...nel.org>, "David S . Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Heiko Stuebner <heiko@...ech.de>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Chris Morgan <macromorgan@...mail.com>, 
	Linus Walleij <linus.walleij@...aro.org>, Geert Uytterhoeven <geert+renesas@...der.be>, 
	Arnd Bergmann <arnd@...db.de>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Nícolas F . R . A . Prado <nfraprado@...labora.com>, 
	Marek Szyprowski <m.szyprowski@...sung.com>, Peng Fan <peng.fan@....com>, 
	Robert Richter <rrichter@....com>, Dan Williams <dan.j.williams@...el.com>, 
	Jonathan Cameron <Jonathan.Cameron@...wei.com>, Terry Bowman <terry.bowman@....com>, 
	Lukas Wunner <lukas@...ner.de>, Huacai Chen <chenhuacai@...nel.org>, Alex Elder <elder@...aro.org>, 
	Srini Kandagatla <srinivas.kandagatla@...aro.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Abel Vesa <abel.vesa@...aro.org>, 
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-pci@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 0/9] PCI: introduce the concept of power sequencing of
 PCIe devices

On Fri, Jan 19, 2024 at 3:11 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
> On Fri, Jan 19, 2024 at 3:07 PM Dmitry Baryshkov
> <dmitry.baryshkov@...aro.org> wrote:
> >
>
> [snip]
>
> > > >
> > >
> > > Alright, so let's imagine we do model the PMU on the device tree. It would
> > > look something like this:
> > >
> > > qca6390_pmu: pmic@0 {
> > >         compatible = "qcom,qca6390-pmu";
> > >
> > >         bt-gpios = <...>;
> > >         wlan-gpios = <...>;
> > >
> > >         vdd-supply = <&vreg...>;
> > >         ...
> > >
> > >         regulators-0 {
> > >                 vreg_x: foo {
> > >                         ...
> > >                 };
> > >
> > >                 ...
> > >         };
> > > };
> > >
> > > Then the WLAN and BT consume the regulators from &qca6390_pmu. Obviously we
> > > cannot go:
> > >
> > > wlan {
> > >         pwrseq = &qca6390_pmu;
> > > };
> > >
> > > But it's enough to:
> > >
> > > wlan {
> > >         vdd-supply = <&vreg_x>;
> > > };
> >
> > I'm not sure this will fly. This means expecting that regulator
> > framework is reentrant, which I think is not the case.
> >
>
> Oh maybe I didn't make myself clear. That's the DT representation of
> HW. With pwrseq, the BT or ATH11K drivers wouldn't use the regulator
> framework. They would use the pwrseq framework and it could use the
> phandle of the regulator to get into the correct pwrseq device without
> making Rob and Krzysztof angry.
>
> Bart
>
> [snip]

I'm working on a PoC of the generic pwrseq framework but without the
explicit pwrseq modelling in DT. Should have an RFC ready early next
week.

Bart