ARM: mach-shmobile: Flush caches in platform_cpu_die()

Add cache flushing code to the SH-Mobile specific CPU hotplug
implementation. While at it, add a cpu mask to make sure the
cache flushing code is finished in platform_cpu_die() before
letting the SoC-specific code in shmobile_platform_cpu_kill()
proceed with turning off power.

Without this code CPU hotplug offline fails when cache is
enabled on Cortex-A9 based SoCs.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 30 insertions, 1 deletions

diff --git a/arch/arm/mach-shmobile/hotplug.c b/arch/arm/mach-shmobile/hotplug.c
index aee3a1088a5a..828d22f3af57 100644
--- a/arch/arm/mach-shmobile/hotplug.c
+++ b/arch/arm/mach-shmobile/hotplug.c
@@ -12,15 +12,43 @@
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/smp.h>
+#include <linux/cpumask.h>
+#include <linux/delay.h>
 #include <mach/common.h>
+#include <asm/cacheflush.h>
+
+static cpumask_t dead_cpus;
 
 int platform_cpu_kill(unsigned int cpu)
 {
-        return shmobile_platform_cpu_kill(cpu);
+        int k;
+
+        /* this function is running on another CPU than the offline target,
+         * here we need wait for shutdown code in platform_cpu_die() to
+         * finish before asking SoC-specific code to power off the CPU core.
+         */
+        for (k = 0; k < 1000; k++) {
+                if (cpumask_test_cpu(cpu, &dead_cpus))
+                        return shmobile_platform_cpu_kill(cpu);
+
+                mdelay(1);
+        }
+
+        return 0;
 }
 
 void platform_cpu_die(unsigned int cpu)
 {
+        /* hardware shutdown code running on the CPU that is being offlined */
+        flush_cache_all();
+        dsb();
+
+        /* notify platform_cpu_kill() that hardware shutdown is finished */
+        cpumask_set_cpu(cpu, &dead_cpus);
+
+        /* wait for SoC code in platform_cpu_kill() to shut off CPU core
+         * power. CPU bring up starts from the reset vector.
+         */
         while (1) {
                 /*
                  * here's the WFI
@@ -34,6 +62,7 @@ void platform_cpu_die(unsigned int cpu)
 
 int platform_cpu_disable(unsigned int cpu)
 {
+        cpumask_clear_cpu(cpu, &dead_cpus);
         /*
          * we don't allow CPU 0 to be shutdown (it is still too special
          * e.g. clock tick interrupts)