[POWERPC] powermac: Support G5 CPU hotplug

This allows "hotplugging" of CPUs on G5 machines.  CPUs that are
disabled are put into an idle loop with the decrementer frequency set
to minimum.  To wake them up again we kick them just like when bringing
them up.  To stop those CPUs from messing with any global state we stop
them from entering the timer interrupt.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/idle_power4.S b/arch/powerpc/kernel/idle_power4.S
index ba3195478600..5328709eeedc 100644
--- a/arch/powerpc/kernel/idle_power4.S
+++ b/arch/powerpc/kernel/idle_power4.S
@@ -53,3 +53,24 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
         isync
         b       1b
 
+_GLOBAL(power4_cpu_offline_powersave)
+        /* Go to NAP now */
+        mfmsr   r7
+        rldicl  r0,r7,48,1
+        rotldi  r0,r0,16
+        mtmsrd  r0,1                    /* hard-disable interrupts */
+        li      r0,1
+        li      r6,0
+        stb     r0,PACAHARDIRQEN(r13)   /* we'll hard-enable shortly */
+        stb     r6,PACASOFTIRQEN(r13)   /* soft-disable irqs */
+BEGIN_FTR_SECTION
+        DSSALL
+        sync
+END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
+        ori     r7,r7,MSR_EE
+        oris    r7,r7,MSR_POW@h
+        sync
+        isync
+        mtmsrd  r7
+        isync
+        blr