[PATCH 2/2] pmdomain: core: Initialize state_idx to deepest state for OFF domains

[Maulik Shah <maulik.shah@oss.qualcomm.com>]

pm_genpd_init() sets genpd->status from is_off but never touches state_idx,
which stays at its kzalloc'd value of 0 (dt_idle_pd_alloc()) regardless of
is_off. A domain that starts OFF without ever having gone through an actual
power-off sequence is therefore left looking like it's parked at its
shallowest idle state (state_idx=0) instead of its deepest one, even though
it is fully powered down.

This is visible on hamoa, where cluster0/1/2 each expose two idle states,
CL4 (state_idx=0) and CL5 (state_idx=1, the deepest). When CPU-cluster
genpds are initialised directly into GENPD_STATE_OFF under OSI mode
("cpuidle: psci: Start CPU-cluster pmdomain OFF when OSI is used"),
clusters whose CPUs are excluded at boot (e.g. maxcpus=4, leaving clusters
1 and 2 untouched) never go through a power-off path, so their state_idx
remains 0 instead of the deepest 1. debugfs reports this as "off-0",
meaning the domain is off but parked at idle-state 0 (CL4) rather than
"off-1", idle-state 1 (CL5):

genpd_power_off() and genpd_sync_power_off() both gate parent power-off on
every child being at its deepest state index:

  if (child->state_idx < child->state_count - 1)
      return;

so the parent's check treats these fully-off children as "not yet at
deepest state" and refuses to power off, blocking the deepest system-level
low-power mode (SS3) from ever being entered.

Without this change:

  $ cat .../power-domain-cpu-cluster1/current_state
  off-0

  $ cat /sys/kernel/debug/qcom_stats/apss
  Count: 0
  Last Entered At: 0
  Last Exited At: 0
  Accumulated Duration: 0

Fix this at the source: when a domain is initialised OFF, set its state_idx
to its deepest state (state_count - 1) instead of leaving it at 0. This
makes genpd's reported state consistent with reality for every is_off=true
caller of pm_genpd_init(), not just the PSCI CPU-cluster case, and requires
no special-casing in the parent power-off checks.

With this change, the domain correctly reports its deepest state and SS3
is entered normally:

  $ cat .../power-domain-cpu-cluster1/current_state
  off-1

  $ cat /sys/kernel/debug/qcom_stats/apss
  Count: 218
  Last Entered At: 726792712
  Last Exited At: 726950687
  Accumulated Duration: 199888773

Fixes: e7d90cfac551 ("PM: domains: Prevent power off for parent unless child is in deepest state")
Assisted-by: Claude:claude-sonnet-5
Signed-off-by: Maulik Shah <maulik.shah@oss.qualcomm.com>
---
 drivers/pmdomain/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
index 842c4169e290..5d96d9eabc1f 100644
--- a/drivers/pmdomain/core.c
+++ b/drivers/pmdomain/core.c
@@ -2409,6 +2409,8 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
 	INIT_WORK(&genpd->power_off_work, genpd_power_off_work_fn);
 	atomic_set(&genpd->sd_count, 0);
 	genpd->status = is_off ? GENPD_STATE_OFF : GENPD_STATE_ON;
+	if (is_off && genpd->state_count)
+		genpd->state_idx = genpd->state_count - 1;
 	genpd_set_stay_on(genpd, is_off);
 	genpd->sync_state = GENPD_SYNC_STATE_OFF;
 	genpd->device_count = 0;

-- 
2.43.0