cpuidle: PSCI: Improve support for suspend-to-RAM for PSCI OSI mode

[ Upstream commit 171b66e ]

When PSCI OSI mode is supported the syscore flag is set for the CPU devices
that becomes attached to their PM domains (genpds). In the suspend-to-idle
case, we call dev_pm_genpd_suspend|resume() to allow genpd to properly
manage the power-off/on operations (pick an idlestate and manage the on/off
notifications).

For suspend-to-ram, dev_pm_genpd_suspend|resume() is currently not being
called, which causes a problem that the genpd on/off notifiers do not get
sent as expected. This prevents the platform-specific operations from being
executed, typically needed just before/after the boot CPU is being turned
off/on.

To deal with this problem, let's register a syscore ops for cpuidle-psci
when PSCI OSI mode is being used and call dev_pm_genpd_suspend|resume()
from them. In this way, genpd regains control of the PM domain topology and
then sends the on/off notifications when it's appropriate.

Reported-by: Maulik Shah <quic_mkshah@quicinc.com>
Suggested-by: Maulik Shah <quic_mkshah@quicinc.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Maulik Shah <quic_mkshah@quicinc.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/cpuidle/cpuidle-psci.c

@@ -23,6 +23,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/syscore_ops.h>
 
 #include <asm/cpuidle.h>
 
@@ -131,13 +132,58 @@ static int psci_idle_cpuhp_down(unsigned int cpu)
 	return 0;
 }
 
+static void psci_idle_syscore_switch(bool suspend)
+{
+	bool cleared = false;
+	struct device *dev;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		dev = per_cpu_ptr(&psci_cpuidle_data, cpu)->dev;
+
+		if (dev && suspend) {
+			dev_pm_genpd_suspend(dev);
+		} else if (dev) {
+			dev_pm_genpd_resume(dev);
+
+			/* Account for userspace having offlined a CPU. */
+			if (pm_runtime_status_suspended(dev))
+				pm_runtime_set_active(dev);
+
+			/* Clear domain state to re-start fresh. */
+			if (!cleared) {
+				psci_set_domain_state(0);
+				cleared = true;
+			}
+		}
+	}
+}
+
+static int psci_idle_syscore_suspend(void)
+{
+	psci_idle_syscore_switch(true);
+	return 0;
+}
+
+static void psci_idle_syscore_resume(void)
+{
+	psci_idle_syscore_switch(false);
+}
+
+static struct syscore_ops psci_idle_syscore_ops = {
+	.suspend = psci_idle_syscore_suspend,
+	.resume = psci_idle_syscore_resume,
+};
+
 static void psci_idle_init_cpuhp(void)
 {
 	int err;
 
 	if (!psci_cpuidle_use_cpuhp)
 		return;
 
+	register_syscore_ops(&psci_idle_syscore_ops);
+
 	err = cpuhp_setup_state_nocalls(CPUHP_AP_CPU_PM_STARTING,
 					"cpuidle/psci:online",
 					psci_idle_cpuhp_up,