cpuidle: psci: Fix cpuhotplug routine with PREEMPT_RT=y

commit 621a88d upstream.

Currently cpu hotplug with the PREEMPT_RT option set in the kernel is
not supported because the underlying generic power domain functions
used in the cpu hotplug callbacks are incompatible from a lock point
of view. This situation prevents the suspend to idle to reach the
deepest idle state for the "cluster" as identified in the
undermentioned commit.

Use the compatible ones when PREEMPT_RT is enabled and remove the
boolean disabling the hotplug callbacks with this option.

With this change the platform can reach the deepest idle state
allowing at suspend time to consume less power.

Tested-on Lenovo T14s with the following script:

echo 0 > /sys/devices/system/cpu/cpu3/online
BEFORE=$(cat /sys/kernel/debug/pm_genpd/power-domain-cpu-cluster0/idle_states | grep S0 | awk '{ print $3 }') ;
rtcwake -s 1 -m mem;
AFTER=$(cat /sys/kernel/debug/pm_genpd/power-domain-cpu-cluster0/idle_states | grep S0 | awk '{ print $3 }');
if [ $BEFORE -lt $AFTER ]; then
    echo "Test successful"
else
    echo "Test failed"
fi
echo 1 > /sys/devices/system/cpu/cpu3/online

Fixes: 1c4b293 ("cpuidle: psci: Enable the hierarchical topology for s2idle on PREEMPT_RT")
Cc: Raghavendra Kakarla <quic_rkakarla@quicinc.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250709154728.733920-1-daniel.lezcano@linaro.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: dlezcano

drivers/cpuidle/cpuidle-psci.c

@@ -38,7 +38,6 @@ struct psci_cpuidle_data {
 static DEFINE_PER_CPU_READ_MOSTLY(struct psci_cpuidle_data, psci_cpuidle_data);
 static DEFINE_PER_CPU(u32, domain_state);
 static bool psci_cpuidle_use_syscore;
-static bool psci_cpuidle_use_cpuhp;
 
 void psci_set_domain_state(u32 state)
 {
@@ -105,8 +104,12 @@ static int psci_idle_cpuhp_up(unsigned int cpu)
 {
 	struct device *pd_dev = __this_cpu_read(psci_cpuidle_data.dev);
 
-	if (pd_dev)
-		pm_runtime_get_sync(pd_dev);
+	if (pd_dev) {
+		if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+			pm_runtime_get_sync(pd_dev);
+		else
+			dev_pm_genpd_resume(pd_dev);
+	}
 
 	return 0;
 }
@@ -116,7 +119,11 @@ static int psci_idle_cpuhp_down(unsigned int cpu)
 	struct device *pd_dev = __this_cpu_read(psci_cpuidle_data.dev);
 
 	if (pd_dev) {
-		pm_runtime_put_sync(pd_dev);
+		if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+			pm_runtime_put_sync(pd_dev);
+		else
+			dev_pm_genpd_suspend(pd_dev);
+
 		/* Clear domain state to start fresh at next online. */
 		psci_set_domain_state(0);
 	}
@@ -177,9 +184,6 @@ static void psci_idle_init_cpuhp(void)
 {
 	int err;
 
-	if (!psci_cpuidle_use_cpuhp)
-		return;
-
 	err = cpuhp_setup_state_nocalls(CPUHP_AP_CPU_PM_STARTING,
 					"cpuidle/psci:online",
 					psci_idle_cpuhp_up,
@@ -240,10 +244,8 @@ static int psci_dt_cpu_init_topology(struct cpuidle_driver *drv,
 	 * s2ram and s2idle.
 	 */
 	drv->states[state_count - 1].enter_s2idle = psci_enter_s2idle_domain_idle_state;
-	if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
 		drv->states[state_count - 1].enter = psci_enter_domain_idle_state;
-		psci_cpuidle_use_cpuhp = true;
-	}
 
 	return 0;
 }
@@ -320,7 +322,6 @@ static void psci_cpu_deinit_idle(int cpu)
 
 	dt_idle_detach_cpu(data->dev);
 	psci_cpuidle_use_syscore = false;
-	psci_cpuidle_use_cpuhp = false;
 }
 
 static int psci_idle_init_cpu(struct device *dev, int cpu)