arm64: add PSCI CPU_OFF-based hotplug support

This patch adds support for using PSCI CPU_OFF calls for CPU hotplug.
With this code it is possible to hot unplug CPUs with "psci" as their
boot-method, as long as there's an appropriate cpu_off function id
specified in the psci node.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
index fb56b61..4f97db3 100644 (file)
--- a/arch/arm64/kernel/psci.c
+++ b/arch/arm64/kernel/psci.c
@@ -256,11 +256,41 @@ static int cpu_psci_cpu_boot(unsigned int cpu)
        return err;
 }
 
+#ifdef CONFIG_HOTPLUG_CPU
+static int cpu_psci_cpu_disable(unsigned int cpu)
+{
+       /* Fail early if we don't have CPU_OFF support */
+       if (!psci_ops.cpu_off)
+               return -EOPNOTSUPP;
+       return 0;
+}
+
+static void cpu_psci_cpu_die(unsigned int cpu)
+{
+       int ret;
+       /*
+        * There are no known implementations of PSCI actually using the
+        * power state field, pass a sensible default for now.
+        */
+       struct psci_power_state state = {
+               .type = PSCI_POWER_STATE_TYPE_POWER_DOWN,
+       };
+
+       ret = psci_ops.cpu_off(state);
+
+       pr_crit("psci: unable to power off CPU%u (%d)\n", cpu, ret);
+}
+#endif
+
 const struct cpu_operations cpu_psci_ops = {
        .name           = "psci",
        .cpu_init       = cpu_psci_cpu_init,
        .cpu_prepare    = cpu_psci_cpu_prepare,
        .cpu_boot       = cpu_psci_cpu_boot,
+#ifdef CONFIG_HOTPLUG_CPU
+       .cpu_disable    = cpu_psci_cpu_disable,
+       .cpu_die        = cpu_psci_cpu_die,
+#endif
 };
 
 #endif