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>

diff --git a/arch/arm/mach-shmobile/hotplug.c b/arch/arm/mach-shmobile/hotplug.c
index aee3a10..828d22f 100644 (file)
--- 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)