[RFC PATCH 3/3] cpuidle: psci: Initialize the PM domains in powered off state for OSI

[Ulf Hansson]

From: Ulf Hansson <ulfh@xxxxxxxxxx>

At the point when the PM domain and the topology are registered through the
genpd subsystem, it's not really known whether corresponding CPUs are
online and thus if the PM domain should be initialized as powered on or
not. Instead this information becomes available when the CPU devices gets
attached to their respective PM domain through dt_idle_attach_cpu().

This is a problem when using PSCI OS-initiated mode, as we may end up with
a PM domain that has the genpd's status indicating it to be powered on,
while it in fact may not be the case. In the less severe scenario, this
leads to selecting a shallower domain idle state for the PM domain than
necessary. A more critical problem is when a non-CPU device shares the PM
domain, leading to their corresponding drivers not being able to trust the
status of it.

Let's fix these problems by initializing the state for the genpd's to be
powered off and in the deepest possible domain idle state, when using
OS-initiated mode. The support for ->sync_state() is maintained by setting
the GENPD_FLAG_OFF_STAY_ON for the genpds in question.

Reported-by: Maulik Shah <maulik.shah@xxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/20260811-domain_off_ss3-v1-0-6a0a0fc023f5@xxxxxxxxxxxxxxxx/
Signed-off-by: Ulf Hansson <ulfh@xxxxxxxxxx>
---
 drivers/cpuidle/cpuidle-psci-domain.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
index b9e4ad7d43a3..29caf3114185 100644
--- a/drivers/cpuidle/cpuidle-psci-domain.c
+++ b/drivers/cpuidle/cpuidle-psci-domain.c
@@ -68,7 +68,8 @@ static int psci_pd_init(struct device_node *np, bool use_osi)
 	 */
 	if (use_osi) {
 		pd->power_off = psci_pd_power_off;
-		pd->flags |= GENPD_FLAG_ACTIVE_WAKEUP;
+		pd->flags |= GENPD_FLAG_ACTIVE_WAKEUP | GENPD_FLAG_OFF_STAY_ON;
+		pd->state_idx = pd->state_count ? pd->state_count - 1 : 0;
 		if (IS_ENABLED(CONFIG_PREEMPT_RT))
 			pd->flags |= GENPD_FLAG_RPM_ALWAYS_ON;
 	} else {
@@ -78,7 +79,7 @@ static int psci_pd_init(struct device_node *np, bool use_osi)
 	/* Use governor for CPU PM domains if it has some states to manage. */
 	pd_gov = pd->states ? &pm_domain_cpu_gov : NULL;
 
-	ret = pm_genpd_init(pd, pd_gov, false);
+	ret = pm_genpd_init(pd, pd_gov, !use_osi);
 	if (ret)
 		goto free_pd_prov;
 
-- 
2.43.0