On Thu, 11 Sept 2025 at 09:56, Geert Uytterhoeven [off-list ref] wrote:

Hi Ulf,

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

quoted

Recent changes to genpd prevents those PM domains being powered-on during
initialization from being powered-off during the boot sequence. Based upon
whether CONFIG_PM_CONFIG_PM_GENERIC_DOMAINS_OF is set of not, genpd relies
on the sync_state mechanism or the genpd_power_off_unused() (which is a
late_initcall_sync), to understand when it's okay to allow these PM domains
to be powered-off.

This new behaviour in genpd has lead to problems on different platforms.
Let's therefore restore the behavior of genpd_power_off_unused().
Moreover, let's introduce GENPD_FLAG_NO_STAY_ON, to allow genpd OF
providers to opt-out from the new behaviour.

Link: https://lore.kernel.org/all/20250701114733.636510-1-ulf.hansson@linaro.org/ (local)
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/all/20250902-rk3576-lockup-regression-v1-1-c4a0c9daeb00@collabora.com/ (local)
Reported-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
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>

Thanks for your patch!

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

quoted

--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h

@@ -115,6 +115,12 @@ struct dev_pm_domain_list {
  *                             genpd provider specific way, likely through a
  *                             parent device node. This flag makes genpd to
  *                             skip its internal support for this.
+ *
+ * GENPD_FLAG_NO_STAY_ON:      For genpd OF providers a powered-on PM domain at
+ *                             initialization is prevented from being
+ *                             powered-off until the ->sync_state() callback is
+ *                             invoked. This flag informs genpd to allow a
+ *                             power-off without waiting for ->sync_state().

This also restores power-down of pmdomains after a failed device
probe (due to a real issue, or just -EPROBE_DEFER), possibly
interfering with other devices that are part of the same pmdomain(s)
but haven't been probed yet. E.g. what if your serial console is
part of the same pmdomain?  Probably the pmdomain(s) should not
be powered down immediately, but only later, when either sync state
or genpd_power_off_unused() kicks in.

That is exactly one of the problems we solve with the new sync_state
support in genpd.

If you have this problem for one of the PM domains, we should not set
GENPD_FLAG_NO_STAY_ON for it. In fact, that's exactly why I added this
flag, to allow it to be set on a per genpd basis. Otherwise we might
as well have used of_genpd_sync_state().

Down the road, if we can improve the sync_state support in genpd,
especially a more fine-grained control for those providers that use
of_genpd_add_provider_onecell(), I hope we should be able to remove
this flag.

[...]

Kind regards
Uffe