linux-kernel - Re: [RFC PATCH v1 5/5] ARM64: verdin-imx8mm: use regulator power domain to model sleep-moci

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Message-ID: <CAEHkU3U+Ahk1eyw-dWYM2Egt8xvhyM6piEHbSSq=dyZstomHcg@mail.gmail.com>
Date:   Wed, 15 Jun 2022 17:32:43 +0200
From:   Max Krummenacher <max.oss.09@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Max Krummenacher <max.krummenacher@...adex.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Francesco Dolcini <francesco.dolcini@...adex.com>,
        Mark Brown <broonie@...nel.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Andrejs Cainikovs <andrejs.cainikovs@...adex.com>,
        Fabio Estevam <festevam@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v1 5/5] ARM64: verdin-imx8mm: use regulator power
 domain to model sleep-moci

Hi

On Tue, Jun 14, 2022 at 9:29 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Max,
>
> On Thu, Jun 9, 2022 at 5:16 PM Max Krummenacher <max.oss.09@...il.com> wrote:
> > From: Max Krummenacher <max.krummenacher@...adex.com>
> >
> > The Verdin CTRL_SLEEP_MOCI# pin signals the carrier board that the module
> > is in sleep and it may switch off unneeded power.
> >
> > Control this pin with a regulator power domain controller which uses a
> > fixed regulator with a gpio enable.
> >
> > Signed-off-by: Max Krummenacher <max.krummenacher@...adex.com>
>
> Thanks for your patch!
>
> > --- a/arch/arm64/boot/dts/freescale/imx8mm-verdin-dahlia.dtsi
> > +++ b/arch/arm64/boot/dts/freescale/imx8mm-verdin-dahlia.dtsi
> > @@ -92,6 +92,7 @@
> >
> >  /* Verdin PCIE_1 */
> >  &pcie0 {
> > +       power-domains = <&pd_sleep_moci>;
>
> This overrides "power-domains = <&pgc_pcie>;" from imx8mm.dtsi...
>
> >         status = "okay";
> >  };
>
> > --- a/arch/arm64/boot/dts/freescale/imx8mm-verdin.dtsi
> > +++ b/arch/arm64/boot/dts/freescale/imx8mm-verdin.dtsi
> > @@ -53,6 +53,14 @@
> >                 };
> >         };
> >
> > +       pd_sleep_moci: power-domain-sleep-moci {
> > +               compatible = "regulator-pm-pd";
> > +               label = "pd_sleep_moci";
> > +               power-domains = <&pgc_pcie>;
>
> ... and here you work around that by re-binding <&pgc_pcie>.
>
> I think you:
>   1. must not override the power-domains property for pcie0, as
>      conceptually, the PCIe bus is still in the on-SoC power
>      domain. What if some lanes are connected to devices in
>      pd_sleep_moci, but other lanes are not?
>   2. should only use pd_sleep_moci for the off-chip devices that
>       are actually controlled by the corresponding regulator.

I fully agree.
I wanted to send along the implementation commits for the power
domain controller something which actually uses it and which
did work in my testing.
That is why I marked this as RFC and I know that more
work is needed.

Cheers
Max

>
> > +               power-supply = <&reg_sleep_moci>;
> > +               #power-domain-cells = <0>;
> > +       };
> > +
> >         /* Carrier Board Supplies */
> >         reg_1p8v: regulator-1p8v {
> >                 compatible = "regulator-fixed";
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds