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>

1 files changed, 30 insertions, 0 deletions

diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
index fb56b6158344..4f97db3d7363 100644
--- 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