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

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Max,

On Thu, Jun 9, 2022 at 5:16 PM Max Krummenacher <max.oss.09@gmail.com> wrote:
> From: Max Krummenacher <max.krummenacher@toradex.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@toradex.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.

> +               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@linux-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