[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>

2 files changed, 56 insertions, 31 deletions

diff --git a/arch/ppc/platforms/pmac_sleep.S b/arch/ppc/platforms/pmac_sleep.S
index 8d67adc7692..88419c77ac4 100644
--- a/arch/ppc/platforms/pmac_sleep.S
+++ b/arch/ppc/platforms/pmac_sleep.S
@@ -161,6 +161,8 @@ _GLOBAL(low_sleep_handler)
 	addi r3,r3,sleep_storage@l
 	stw r5,0(r3)
 
+	.globl	low_cpu_die
+low_cpu_die:
 	/* Flush & disable all caches */
 	bl	flush_disable_caches
 
diff --git a/arch/ppc/platforms/pmac_smp.c b/arch/ppc/platforms/pmac_smp.c
index 8e049dab4e6..794a23994b8 100644
--- a/arch/ppc/platforms/pmac_smp.c
+++ b/arch/ppc/platforms/pmac_smp.c
@@ -33,6 +33,7 @@
 #include <linux/spinlock.h>
 #include <linux/errno.h>
 #include <linux/hardirq.h>
+#include <linux/cpu.h>
 
 #include <asm/ptrace.h>
 #include <asm/atomic.h>
@@ -55,9 +56,7 @@
  * Powersurge (old powermac SMP) support.
  */
 
-extern void __secondary_start_psurge(void);
-extern void __secondary_start_psurge2(void);	/* Temporary horrible hack */
-extern void __secondary_start_psurge3(void);	/* Temporary horrible hack */
+extern void __secondary_start_pmac_0(void);
 
 /* Addresses for powersurge registers */
 #define HAMMERHEAD_BASE		0xf8000000
@@ -119,7 +118,7 @@ static volatile int sec_tb_reset = 0;
 static unsigned int pri_tb_hi, pri_tb_lo;
 static unsigned int pri_tb_stamp;
 
-static void __init core99_init_caches(int cpu)
+static void __devinit core99_init_caches(int cpu)
 {
 	if (!cpu_has_feature(CPU_FTR_L2CR))
 		return;
@@ -346,7 +345,7 @@ static int __init smp_psurge_probe(void)
 
 static void __init smp_psurge_kick_cpu(int nr)
 {
-	void (*start)(void) = __secondary_start_psurge;
+	unsigned long start = __pa(__secondary_start_pmac_0) + nr * 8;
 	unsigned long a;
 
 	/* may need to flush here if secondary bats aren't setup */
@@ -356,17 +355,7 @@ static void __init smp_psurge_kick_cpu(int nr)
 
 	if (ppc_md.progress) ppc_md.progress("smp_psurge_kick_cpu", 0x353);
 
-	/* setup entry point of secondary processor */
-	switch (nr) {
-	case 2:
-		start = __secondary_start_psurge2;
-		break;
-	case 3:
-		start = __secondary_start_psurge3;
-		break;
-	}
-
-	out_be32(psurge_start, __pa(start));
+	out_be32(psurge_start, start);
 	mb();
 
 	psurge_set_ipi(nr);
@@ -500,14 +489,14 @@ static int __init smp_core99_probe(void)
 	return ncpus;
 }
 
-static void __init smp_core99_kick_cpu(int nr)
+static void __devinit smp_core99_kick_cpu(int nr)
 {
 	unsigned long save_vector, new_vector;
 	unsigned long flags;
 
 	volatile unsigned long *vector
 		 = ((volatile unsigned long *)(KERNELBASE+0x100));
-	if (nr < 1 || nr > 3)
+	if (nr < 0 || nr > 3)
 		return;
 	if (ppc_md.progress) ppc_md.progress("smp_core99_kick_cpu", 0x346);
 
@@ -518,19 +507,9 @@ static void __init smp_core99_kick_cpu(int nr)
 	save_vector = *vector;
 
 	/* Setup fake reset vector that does	
-	 *   b __secondary_start_psurge - KERNELBASE
+	 *   b __secondary_start_pmac_0 + nr*8 - KERNELBASE
 	 */
-	switch(nr) {
-		case 1:
-			new_vector = (unsigned long)__secondary_start_psurge;
-			break;
-		case 2:
-			new_vector = (unsigned long)__secondary_start_psurge2;
-			break;
-		case 3:
-			new_vector = (unsigned long)__secondary_start_psurge3;
-			break;
-	}
+	new_vector = (unsigned long) __secondary_start_pmac_0 + nr * 8;
 	*vector = 0x48000002 + new_vector - KERNELBASE;
 
 	/* flush data cache and inval instruction cache */
@@ -554,7 +533,7 @@ static void __init smp_core99_kick_cpu(int nr)
 	if (ppc_md.progress) ppc_md.progress("smp_core99_kick_cpu done", 0x347);
 }
 
-static void __init smp_core99_setup_cpu(int cpu_nr)
+static void __devinit smp_core99_setup_cpu(int cpu_nr)
 {
 	/* Setup L2/L3 */
 	if (cpu_nr != 0)
@@ -668,3 +647,47 @@ struct smp_ops_t core99_smp_ops __pmacdata = {
 	.give_timebase	= smp_core99_give_timebase,
 	.take_timebase	= smp_core99_take_timebase,
 };
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+int __cpu_disable(void)
+{
+	cpu_clear(smp_processor_id(), cpu_online_map);
+
+	/* XXX reset cpu affinity here */
+	openpic_set_priority(0xf);
+	asm volatile("mtdec %0" : : "r" (0x7fffffff));
+	mb();
+	udelay(20);
+	asm volatile("mtdec %0" : : "r" (0x7fffffff));
+	return 0;
+}
+
+extern void low_cpu_die(void) __attribute__((noreturn)); /* in pmac_sleep.S */
+static int cpu_dead[NR_CPUS];
+
+void cpu_die(void)
+{
+	local_irq_disable();
+	cpu_dead[smp_processor_id()] = 1;
+	mb();
+	low_cpu_die();
+}
+
+void __cpu_die(unsigned int cpu)
+{
+	int timeout;
+
+	timeout = 1000;
+	while (!cpu_dead[cpu]) {
+		if (--timeout == 0) {
+			printk("CPU %u refused to die!\n", cpu);
+			break;
+		}
+		msleep(1);
+	}
+	cpu_callin_map[cpu] = 0;
+	cpu_dead[cpu] = 0;
+}
+
+#endif