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

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>

1 files changed, 46 insertions, 0 deletions

diff --git a/drivers/cpuidle/cpuidle-psci.c b/drivers/cpuidle/cpuidle-psci.c
index b51b5df08450..540105ca0781 100644
--- a/drivers/cpuidle/cpuidle-psci.c
+++ b/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>
 
@@ -131,6 +132,49 @@ 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;
@@ -138,6 +182,8 @@ static void psci_idle_init_cpuhp(void)
 	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,