[PATCH 3/5] pmdomain: renesas: rcar-sysc: Don't keep unused PM domains powered-on

[Geert Uytterhoeven]

Hi Ulf,

On Tue, 9 Sept 2025 at 13:11, Ulf Hansson <ulf.hansson at linaro.org> wrote:
> The recent changes to genpd makes a genpd OF provider that is powered-on at
> initialization to stay powered-on, until the ->sync_state() callback is
> invoked for it.
>
> This may not happen at all, if we wait for a consumer device to be probed,
> leading to wasting energy. There are ways to enforce the ->sync_state()
> callback to be invoked, through sysfs or via the probe-defer-timeout, but
> none of them in its current form are a good fit for rcar-sysc PM domains.
>
> Let's therefore opt-out from this behaviour of genpd for now, by using the
> GENPD_FLAG_NO_STAY_ON.
>
> Link: https://lore.kernel.org/all/20250701114733.636510-1-ulf.hansson@linaro.org/
> Reported-by: Geert Uytterhoeven <geert at linux-m68k.org>
> Fixes: 0e789b491ba0 ("pmdomain: core: Leave powered-on genpds on until sync_state")
> Fixes: 13a4b7fb6260 ("pmdomain: core: Leave powered-on genpds on until late_initcall_sync")
> Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>

> --- a/drivers/pmdomain/renesas/rcar-sysc.c
> +++ b/drivers/pmdomain/renesas/rcar-sysc.c
> @@ -241,6 +241,7 @@ static int __init rcar_sysc_pd_setup(struct rcar_sysc_pd *pd)
>                 }
>         }
>
> +       genpd->flags |= GENPD_FLAG_NO_STAY_ON;

So this applies to all PM Domains.  While this doesn't hurt, perhaps it
should not be set for always-on domains, and thus moved up, to become
an "else" branch in the "if/else if/..."-logic handling always-on
domains at the top of the function?

This applies to rar-gen4-sysc.c, too.

>         genpd->power_off = rcar_sysc_pd_power_off;
>         genpd->power_on = rcar_sysc_pd_power_on;
>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at 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