cpuidle: psci: Drop redundant sync_state support

The recent updates to the genpd core, can entirely manage the sync_state
support for the cpuidle-psci-domain. More precisely, genpd prevents our
->power_off() callback from being invoked, until all of our consumers are
ready for it.

Let's therefore drop the sync_state support for the cpuidle-psci-domain as
it has become redundant.

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/20250701114733.636510-24-ulf.hansson@linaro.org

Author: Ulf Hansson

drivers/cpuidle/cpuidle-psci-domain.c

@@ -28,7 +28,6 @@ struct psci_pd_provider {
 };
 
 static LIST_HEAD(psci_pd_providers);
-static bool psci_pd_allow_domain_state;
 
 static int psci_pd_power_off(struct generic_pm_domain *pd)
 {
@@ -38,9 +37,6 @@ static int psci_pd_power_off(struct generic_pm_domain *pd)
 	if (!state->data)
 		return 0;
 
-	if (!psci_pd_allow_domain_state)
-		return -EBUSY;
-
 	/* OSI mode is enabled, set the corresponding domain state. */
 	pd_state = state->data;
 	psci_set_domain_state(pd, pd->state_idx, *pd_state);
@@ -63,8 +59,7 @@ static int psci_pd_init(struct device_node *np, bool use_osi)
 	if (!pd_provider)
 		goto free_pd;
 
-	pd->flags |= GENPD_FLAG_IRQ_SAFE | GENPD_FLAG_CPU_DOMAIN |
-		     GENPD_FLAG_NO_SYNC_STATE;
+	pd->flags |= GENPD_FLAG_IRQ_SAFE | GENPD_FLAG_CPU_DOMAIN;
 
 	/*
 	 * Allow power off when OSI has been successfully enabled.
@@ -127,20 +122,6 @@ static void psci_pd_remove(void)
 	}
 }
 
-static void psci_cpuidle_domain_sync_state(struct device *dev)
-{
-	struct psci_pd_provider *pd_provider;
-
-	/*
-	 * All devices have now been attached/probed to the PM domain topology,
-	 * hence it's fine to allow domain states to be picked.
-	 */
-	psci_pd_allow_domain_state = true;
-
-	list_for_each_entry(pd_provider, &psci_pd_providers, link)
-		of_genpd_sync_state(pd_provider->node);
-}
-
 static const struct of_device_id psci_of_match[] = {
 	{ .compatible = "arm,psci-1.0" },
 	{}
@@ -201,7 +182,6 @@ static struct platform_driver psci_cpuidle_domain_driver = {
 	.driver = {
 		.name = "psci-cpuidle-domain",
 		.of_match_table = psci_of_match,
-		.sync_state = psci_cpuidle_domain_sync_state,
 	},
 };