[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>
diff --git a/arch/ppc/kernel/smp.c b/arch/ppc/kernel/smp.c
index e70b587..726fe7c 100644
--- a/arch/ppc/kernel/smp.c
+++ b/arch/ppc/kernel/smp.c
@@ -45,6 +45,7 @@
cpumask_t cpu_possible_map;
int smp_hw_index[NR_CPUS];
struct thread_info *secondary_ti;
+static struct task_struct *idle_tasks[NR_CPUS];
EXPORT_SYMBOL(cpu_online_map);
EXPORT_SYMBOL(cpu_possible_map);
@@ -286,7 +287,8 @@
void __init smp_prepare_cpus(unsigned int max_cpus)
{
- int num_cpus, i;
+ int num_cpus, i, cpu;
+ struct task_struct *p;
/* Fixup boot cpu */
smp_store_cpu_info(smp_processor_id());
@@ -308,6 +310,17 @@
if (smp_ops->space_timers)
smp_ops->space_timers(num_cpus);
+
+ for_each_cpu(cpu) {
+ if (cpu == smp_processor_id())
+ continue;
+ /* create a process for the processor */
+ p = fork_idle(cpu);
+ if (IS_ERR(p))
+ panic("failed fork for CPU %u: %li", cpu, PTR_ERR(p));
+ p->thread_info->cpu = cpu;
+ idle_tasks[cpu] = p;
+ }
}
void __devinit smp_prepare_boot_cpu(void)
@@ -334,12 +347,17 @@
set_dec(tb_ticks_per_jiffy);
cpu_callin_map[cpu] = 1;
- printk("CPU %i done callin...\n", cpu);
+ printk("CPU %d done callin...\n", cpu);
smp_ops->setup_cpu(cpu);
- printk("CPU %i done setup...\n", cpu);
- local_irq_enable();
+ printk("CPU %d done setup...\n", cpu);
smp_ops->take_timebase();
- printk("CPU %i done timebase take...\n", cpu);
+ printk("CPU %d done timebase take...\n", cpu);
+
+ spin_lock(&call_lock);
+ cpu_set(cpu, cpu_online_map);
+ spin_unlock(&call_lock);
+
+ local_irq_enable();
cpu_idle();
return 0;
@@ -347,17 +365,11 @@
int __cpu_up(unsigned int cpu)
{
- struct task_struct *p;
char buf[32];
int c;
- /* create a process for the processor */
- /* only regs.msr is actually used, and 0 is OK for it */
- p = fork_idle(cpu);
- if (IS_ERR(p))
- panic("failed fork for CPU %u: %li", cpu, PTR_ERR(p));
- secondary_ti = p->thread_info;
- p->thread_info->cpu = cpu;
+ secondary_ti = idle_tasks[cpu]->thread_info;
+ mb();
/*
* There was a cache flush loop here to flush the cache
@@ -389,7 +401,11 @@
printk("Processor %d found.\n", cpu);
smp_ops->give_timebase();
- cpu_set(cpu, cpu_online_map);
+
+ /* Wait until cpu puts itself in the online map */
+ while (!cpu_online(cpu))
+ cpu_relax();
+
return 0;
}