[PATCH v2 6/7] ARM64: smp: Add runtime PM support for CPU hotplug

[Lina Iyer]

Enable runtime PM for CPU devices. Do a runtime get of the CPU device
when the CPU is hotplugged in and runtime put of the CPU device when the
CPU is hotplugged off. When all the CPUs in a domain are hotplugged off,
the domain may also be powered off and cluster_pm_enter/exit()
notifications are be sent out.

Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
Signed-off-by: Lina Iyer <lina.iyer at linaro.org>
---
 arch/arm64/kernel/smp.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index dbdaacd..4076962 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -135,6 +135,7 @@ asmlinkage void secondary_start_kernel(void)
 {
 	struct mm_struct *mm = &init_mm;
 	unsigned int cpu = smp_processor_id();
+	struct device *cpu_dev;
 
 	/*
 	 * All kernel threads share the same mm context; grab a
@@ -185,6 +186,11 @@ asmlinkage void secondary_start_kernel(void)
 	local_irq_enable();
 	local_async_enable();
 
+	/* We are running, enable runtime PM for the CPU. */
+	cpu_dev = get_cpu_device(cpu);
+	if (cpu_dev)
+		pm_runtime_get_sync(cpu_dev);
+
 	/*
 	 * OK, it's off to the idle thread for us
 	 */
@@ -292,6 +298,16 @@ void __cpu_die(unsigned int cpu)
 void cpu_die(void)
 {
 	unsigned int cpu = smp_processor_id();
+	struct device *cpu_dev;
+
+	/*
+	 * We dont need the CPU device anymore.
+	 * Lets do this before IRQs are disabled to allow
+	 * runtime PM to suspend the domain as well.
+	 */
+	cpu_dev = get_cpu_device(cpu);
+	if (cpu_dev)
+		pm_runtime_put_sync(cpu_dev);
 
 	idle_task_exit();
 
-- 
2.1.4