Re: [PATCH/RFC] pmdomain: core: Support pd_ignore_unused with sync_state

[Geert Uytterhoeven]

Hi Ulf,

On Wed, 4 Mar 2026 at 11:56, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> On Mon, 16 Feb 2026 at 19:47, Geert Uytterhoeven
> <geert+renesas@xxxxxxxxx> wrote:
> > Since the introduction of the sync_state mechanism, the
> > "pd_ignore_unused" kernel command line option doesn't really work
> > anymore.  While genpd_power_off_unused() still checks for that flag
> > before powering down unused domains, the new sync_state callbacks lack
> > such checks, thus powering down unused domains regardless.
> >
> > Fix this by adding checks to the sync_state helpers and callbacks.
> > Factor out the printing of the warning message, to make sure it is
> > printed only once.
> >
> > Fixes: 002ebddd695a5399 ("pmdomain: core: Restore behaviour for disabling unused PM domains")
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> > ---
> > RFC as I have no need for this in upstream.
>
> I am trying to understand the use case and whether we should consider
> to land this upstream.
>
> Would you mind elaborating on how this is useful for you?

It is (currently) not useful for me, but it may be useful for others.
During work on a new SoC, someone had hardcoded "pd_ignore_unused"
in the kernel command line.  After adding support for PM Domains on
that SoC, I noticed PM Domains were still powered down.

The issue is that pd_ignore_unused no longer does what it claims to do:

        pd_ignore_unused
                        [PM]
                        Keep all power-domains already enabled by bootloader on,
                        even if no driver has claimed them. This is useful
                        for debug and development, but should not be
                        needed on a platform with proper driver support.

So IMO that should either be fixed, or the option should be removed.
Do you agree?
Thanks!

Gr{oetje,eeting}s,

                        Geert

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

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