3 files changed, 56 insertions, 0 deletions

diff --git a/arch/arm/common/mcpm_entry.c b/arch/arm/common/mcpm_entry.c
index 990250965f2c..6c03d0152e7f 100644
--- a/arch/arm/common/mcpm_entry.c
+++ b/arch/arm/common/mcpm_entry.c
@@ -90,6 +90,21 @@ void mcpm_cpu_power_down(void)
         BUG();
 }
 
+int mcpm_cpu_power_down_finish(unsigned int cpu, unsigned int cluster)
+{
+        int ret;
+
+        if (WARN_ON_ONCE(!platform_ops || !platform_ops->power_down_finish))
+                return -EUNATCH;
+
+        ret = platform_ops->power_down_finish(cpu, cluster);
+        if (ret)
+                pr_warn("%s: cpu %u, cluster %u failed to power down (%d)\n",
+                        __func__, cpu, cluster, ret);
+
+        return ret;
+}
+
 void mcpm_cpu_suspend(u64 expected_residency)
 {
         phys_reset_t phys_reset;
diff --git a/arch/arm/common/mcpm_platsmp.c b/arch/arm/common/mcpm_platsmp.c
index c0c3cd799ccc..177251a4dd9a 100644
--- a/arch/arm/common/mcpm_platsmp.c
+++ b/arch/arm/common/mcpm_platsmp.c
@@ -56,6 +56,15 @@ static void mcpm_secondary_init(unsigned int cpu)
 
 #ifdef CONFIG_HOTPLUG_CPU
 
+static int mcpm_cpu_kill(unsigned int cpu)
+{
+        unsigned int pcpu, pcluster;
+
+        cpu_to_pcpu(cpu, &pcpu, &pcluster);
+
+        return !mcpm_cpu_power_down_finish(pcpu, pcluster);
+}
+
 static int mcpm_cpu_disable(unsigned int cpu)
 {
         /*
@@ -82,6 +91,7 @@ static struct smp_operations __initdata mcpm_smp_ops = {
         .smp_boot_secondary     = mcpm_boot_secondary,
         .smp_secondary_init     = mcpm_secondary_init,
 #ifdef CONFIG_HOTPLUG_CPU
+        .cpu_kill               = mcpm_cpu_kill,
         .cpu_disable            = mcpm_cpu_disable,
         .cpu_die                = mcpm_cpu_die,
 #endif
diff --git a/arch/arm/include/asm/mcpm.h b/arch/arm/include/asm/mcpm.h
index fc82a88f5b69..1cf26010a6f3 100644
--- a/arch/arm/include/asm/mcpm.h
+++ b/arch/arm/include/asm/mcpm.h
@@ -81,10 +81,40 @@ int mcpm_cpu_power_up(unsigned int cpu, unsigned int cluster);
  *
  * This will return if mcpm_platform_register() has not been called
  * previously in which case the caller should take appropriate action.
+ *
+ * On success, the CPU is not guaranteed to be truly halted until
+ * mcpm_cpu_power_down_finish() subsequently returns non-zero for the
+ * specified cpu.  Until then, other CPUs should make sure they do not
+ * trash memory the target CPU might be executing/accessing.
  */
 void mcpm_cpu_power_down(void);
 
 /**
+ * mcpm_cpu_power_down_finish - wait for a specified CPU to halt, and
+ *      make sure it is powered off
+ *
+ * @cpu: CPU number within given cluster
+ * @cluster: cluster number for the CPU
+ *
+ * Call this function to ensure that a pending powerdown has taken
+ * effect and the CPU is safely parked before performing non-mcpm
+ * operations that may affect the CPU (such as kexec trashing the
+ * kernel text).
+ *
+ * It is *not* necessary to call this function if you only need to
+ * serialise a pending powerdown with mcpm_cpu_power_up() or a wakeup
+ * event.
+ *
+ * Do not call this function unless the specified CPU has already
+ * called mcpm_cpu_power_down() or has committed to doing so.
+ *
+ * @return:
+ *      - zero if the CPU is in a safely parked state
+ *      - nonzero otherwise (e.g., timeout)
+ */
+int mcpm_cpu_power_down_finish(unsigned int cpu, unsigned int cluster);
+
+/**
  * mcpm_cpu_suspend - bring the calling CPU in a suspended state
  *
  * @expected_residency: duration in microseconds the CPU is expected
@@ -126,6 +156,7 @@ int mcpm_cpu_powered_up(void);
 struct mcpm_platform_ops {
         int (*power_up)(unsigned int cpu, unsigned int cluster);
         void (*power_down)(void);
+        int (*power_down_finish)(unsigned int cpu, unsigned int cluster);
         void (*suspend)(u64);
         void (*powered_up)(void);
 };