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

On Thu, 11 Sept 2025 at 11:02, Geert Uytterhoeven [off-list ref] wrote:

Hi Ulf,

On Tue, 9 Sept 2025 at 13:11, Ulf Hansson [off-list ref] wrote:

quoted

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/ (local)
Reported-by: Geert Uytterhoeven <geert@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 <redacted>

quoted

--- 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.

You have a point, but currently this doesn't really matter. Genpd will
not power-off always-on-domains no matter whether
GENPD_FLAG_NO_STAY_ON is set or not.

The whole purpose from my side was to restore the behaviour we had
before, for the Reneas PM domains. I tend to think that it's better to
apply the $subject patch as is - and leave improvements to be made on
top.

Thanks a lot for testing and reviewing!

[...]

Kind regards
Uffe