ARM: 7848/1: mcpm: Implement cpu_kill() to synchronise on powerdown

CPU hotplug and kexec rely on smp_ops.cpu_kill(), which is supposed
to wait for the CPU to park or power down, and perform the last
rites (such as disabling clocks etc., where the platform doesn't do
this automatically).

kexec in particular is unsafe without performing this
synchronisation to park secondaries.  Without it, the secondaries
might not be parked when kexec trashes the kernel.

There is no generic way to do this synchronisation, so a new mcpm
platform_ops method power_down_finish() is added by this patch.

The new method is mandatory.  A platform which provides no way to
detect when CPUs are parked is likely broken.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 15 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;