[PATCH] ppc32: support hotplug cpu on powermacs

This allows cpus to be off-lined on 32-bit SMP powermacs.  When a cpu
is off-lined, it is put into sleep mode with interrupts disabled.  It
can be on-lined again by asserting its soft-reset pin, which is
connected to a GPIO pin.

With this I can off-line the second cpu in my dual G4 powermac, which
means that I can then suspend the machine (the suspend/resume code
refuses to suspend if more than one cpu is online, and making it cope
with multiple cpus is surprisingly messy).

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/ppc/kernel/idle.c b/arch/ppc/kernel/idle.c
index 53547b6de45b..fba29c876b62 100644
--- a/arch/ppc/kernel/idle.c
+++ b/arch/ppc/kernel/idle.c
@@ -22,6 +22,7 @@
 #include <linux/ptrace.h>
 #include <linux/slab.h>
 #include <linux/sysctl.h>
+#include <linux/cpu.h>
 
 #include <asm/pgtable.h>
 #include <asm/uaccess.h>
@@ -35,6 +36,7 @@
 void default_idle(void)
 {
         void (*powersave)(void);
+        int cpu = smp_processor_id();
 
         powersave = ppc_md.power_save;
 
@@ -44,7 +46,7 @@ void default_idle(void)
 #ifdef CONFIG_SMP
                 else {
                         set_thread_flag(TIF_POLLING_NRFLAG);
-                        while (!need_resched())
+                        while (!need_resched() && !cpu_is_offline(cpu))
                                 barrier();
                         clear_thread_flag(TIF_POLLING_NRFLAG);
                 }
@@ -52,6 +54,8 @@ void default_idle(void)
         }
         if (need_resched())
                 schedule();
+        if (cpu_is_offline(cpu) && system_state == SYSTEM_RUNNING)
+                cpu_die();
 }
 
 /*