pmdomain: core: Leave powered-on genpds on until late_initcall_sync

Powering-off a genpd that was on during boot, before all of its consumer
devices have been probed, is certainly prone to problems.

As a step to improve this situation, let's prevent these genpds from being
powered-off until genpd_power_off_unused() gets called, which is a
late_initcall_sync().

Note that, this still doesn't guarantee that all the consumer devices has
been probed before we allow to power-off the genpds. Yet, this should be a
step in the right direction.

Suggested-by: Saravana Kannan <saravanak@google.com>
Tested-by: Hiago De Franco <hiago.franco@toradex.com> # Colibri iMX8X
Tested-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> # TI AM62A,Xilinx ZynqMP ZCU106
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20250701114733.636510-22-ulf.hansson@linaro.org

Author: storulf

drivers/pmdomain/core.c

@@ -931,11 +931,12 @@ static void genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
 	 * The domain is already in the "power off" state.
 	 * System suspend is in progress.
 	 * The domain is configured as always on.
+	 * The domain was on at boot and still need to stay on.
 	 * The domain has a subdomain being powered on.
 	 */
 	if (!genpd_status_on(genpd) || genpd->prepared_count > 0 ||
 	    genpd_is_always_on(genpd) || genpd_is_rpm_always_on(genpd) ||
-	    atomic_read(&genpd->sd_count) > 0)
+	    genpd->stay_on || atomic_read(&genpd->sd_count) > 0)
 		return;
 
 	/*
@@ -1346,8 +1347,12 @@ static int __init genpd_power_off_unused(void)
 	pr_info("genpd: Disabling unused power domains\n");
 	mutex_lock(&gpd_list_lock);
 
-	list_for_each_entry(genpd, &gpd_list, gpd_list_node)
+	list_for_each_entry(genpd, &gpd_list, gpd_list_node) {
+		genpd_lock(genpd);
+		genpd->stay_on = false;
+		genpd_unlock(genpd);
 		genpd_queue_power_off_work(genpd);
+	}
 
 	mutex_unlock(&gpd_list_lock);
 
@@ -2352,6 +2357,7 @@ 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;
+	genpd->stay_on = !is_off;
 	genpd->sync_state = GENPD_SYNC_STATE_OFF;
 	genpd->device_count = 0;
 	genpd->provider = NULL;

include/linux/pm_domain.h

@@ -199,6 +199,7 @@ struct generic_pm_domain {
 	unsigned int performance_state;	/* Aggregated max performance state */
 	cpumask_var_t cpus;		/* A cpumask of the attached CPUs */
 	bool synced_poweroff;		/* A consumer needs a synced poweroff */
+	bool stay_on;			/* Stay powered-on during boot. */
 	enum genpd_sync_state sync_state; /* How sync_state is managed. */
 	int (*power_off)(struct generic_pm_domain *domain);
 	int (*power_on)(struct generic_pm_domain *domain);