pmdomain: core: Restore behaviour for disabling unused PM domains

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/
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/all/20250902-rk3576-lockup-regression-v1-1-c4a0c9daeb00@collabora.com/
Reported-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Fixes: 0e789b4 ("pmdomain: core: Leave powered-on genpds on until sync_state")
Fixes: 13a4b7f ("pmdomain: core: Leave powered-on genpds on until late_initcall_sync")
Tested-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Author: storulf

drivers/pmdomain/core.c

@@ -187,6 +187,7 @@ static const struct genpd_lock_ops genpd_raw_spin_ops = {
 #define genpd_is_opp_table_fw(genpd)	(genpd->flags & GENPD_FLAG_OPP_TABLE_FW)
 #define genpd_is_dev_name_fw(genpd)	(genpd->flags & GENPD_FLAG_DEV_NAME_FW)
 #define genpd_is_no_sync_state(genpd)	(genpd->flags & GENPD_FLAG_NO_SYNC_STATE)
+#define genpd_is_no_stay_on(genpd)	(genpd->flags & GENPD_FLAG_NO_STAY_ON)
 
 static inline bool irq_safe_dev_in_sleep_domain(struct device *dev,
 		const struct generic_pm_domain *genpd)
@@ -1357,7 +1358,6 @@ static int genpd_runtime_resume(struct device *dev)
 	return ret;
 }
 
-#ifndef CONFIG_PM_GENERIC_DOMAINS_OF
 static bool pd_ignore_unused;
 static int __init pd_ignore_unused_setup(char *__unused)
 {
@@ -1382,9 +1382,6 @@ static int __init genpd_power_off_unused(void)
 	mutex_lock(&gpd_list_lock);
 
 	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);
 	}
 
@@ -1393,7 +1390,6 @@ static int __init genpd_power_off_unused(void)
 	return 0;
 }
 late_initcall_sync(genpd_power_off_unused);
-#endif
 
 #ifdef CONFIG_PM_SLEEP
 
@@ -2367,6 +2363,18 @@ static void genpd_lock_init(struct generic_pm_domain *genpd)
 	}
 }
 
+#ifdef CONFIG_PM_GENERIC_DOMAINS_OF
+static void genpd_set_stay_on(struct generic_pm_domain *genpd, bool is_off)
+{
+	genpd->stay_on = !genpd_is_no_stay_on(genpd) && !is_off;
+}
+#else
+static void genpd_set_stay_on(struct generic_pm_domain *genpd, bool is_off)
+{
+	genpd->stay_on = false;
+}
+#endif
+
 /**
  * pm_genpd_init - Initialize a generic I/O PM domain object.
  * @genpd: PM domain object to initialize.
@@ -2392,7 +2400,7 @@ 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_set_stay_on(genpd, is_off);
 	genpd->sync_state = GENPD_SYNC_STATE_OFF;
 	genpd->device_count = 0;
 	genpd->provider = NULL;

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().
  */
 #define GENPD_FLAG_PM_CLK	 (1U << 0)
 #define GENPD_FLAG_IRQ_SAFE	 (1U << 1)
@@ -126,6 +132,7 @@ struct dev_pm_domain_list {
 #define GENPD_FLAG_OPP_TABLE_FW	 (1U << 7)
 #define GENPD_FLAG_DEV_NAME_FW	 (1U << 8)
 #define GENPD_FLAG_NO_SYNC_STATE (1U << 9)
+#define GENPD_FLAG_NO_STAY_ON	 (1U << 10)
 
 enum gpd_status {
 	GENPD_STATE_ON = 0,	/* PM domain is on */