[POWERPC] Fix non-MPIC CHRPs with CONFIG_SMP set

Pseudo-CHRP machines like Pegasos without an MPIC would crash at boot if
CONFIG_SMP was set because the "smp_ops" pointer was set to MPIC related
ops unconditionally. This patch makes it NULL on machines that don't
support SMP and provides proper default behaviour in the callers when
smp_ops is NULL.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/smp.c

@@ -144,12 +144,14 @@ void smp_message_recv(int msg, struct pt_regs *regs)
 
 void smp_send_reschedule(int cpu)
 {
+	if (likely(smp_ops))
 		smp_ops->message_pass(cpu, PPC_MSG_RESCHEDULE);
 }
 
 #ifdef CONFIG_DEBUGGER
 void smp_send_debugger_break(int cpu)
 {
+	if (likely(smp_ops))
 		smp_ops->message_pass(cpu, PPC_MSG_DEBUGGER_BREAK);
 }
 #endif
@@ -158,7 +160,7 @@ void smp_send_debugger_break(int cpu)
 void crash_send_ipi(void (*crash_ipi_callback)(struct pt_regs *))
 {
 	crash_ipi_function_ptr = crash_ipi_callback;
-	if (crash_ipi_callback) {
+	if (crash_ipi_callback && smp_ops) {
 		mb();
 		smp_ops->message_pass(MSG_ALL_BUT_SELF, PPC_MSG_DEBUGGER_BREAK);
 	}
@@ -220,6 +222,9 @@ int smp_call_function (void (*func) (void *info), void *info, int nonatomic,
 	/* Can deadlock when called with interrupts disabled */
 	WARN_ON(irqs_disabled());
 
+	if (unlikely(smp_ops == NULL))
+		return -1;
+
 	data.func = func;
 	data.info = info;
 	atomic_set(&data.started, 0);
@@ -357,7 +362,10 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
 	smp_store_cpu_info(boot_cpuid);
 	cpu_callin_map[boot_cpuid] = 1;
 
+	if (smp_ops)
 		max_cpus = smp_ops->probe();
+	else
+		max_cpus = 1;
  
 	smp_space_timers(max_cpus);
 
@@ -453,7 +461,7 @@ void generic_mach_cpu_die(void)
 
 static int __devinit cpu_enable(unsigned int cpu)
 {
-	if (smp_ops->cpu_enable)
+	if (smp_ops && smp_ops->cpu_enable)
 		return smp_ops->cpu_enable(cpu);
 
 	return -ENOSYS;
@@ -467,7 +475,8 @@ int __devinit __cpu_up(unsigned int cpu)
 	if (!cpu_enable(cpu))
 		return 0;
 
-	if (smp_ops->cpu_bootable && !smp_ops->cpu_bootable(cpu))
+	if (smp_ops == NULL ||
+	    (smp_ops->cpu_bootable && !smp_ops->cpu_bootable(cpu)))
 		return -EINVAL;
 
 	/* Make sure callin-map entry is 0 (can be leftover a CPU
@@ -568,6 +577,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
 	old_mask = current->cpus_allowed;
 	set_cpus_allowed(current, cpumask_of_cpu(boot_cpuid));
 	
+	if (smp_ops)
 		smp_ops->setup_cpu(boot_cpuid);
 
 	set_cpus_allowed(current, old_mask);

arch/powerpc/platforms/chrp/setup.c

@@ -291,10 +291,6 @@ void __init chrp_setup_arch(void)
 
 	pci_create_OF_bus_map();
 
-#ifdef CONFIG_SMP
-	smp_ops = &chrp_smp_ops;
-#endif /* CONFIG_SMP */
-
 	/*
 	 * Print the banner, then scroll down so boot progress
 	 * can be printed.  -- Cort
@@ -479,6 +475,14 @@ void __init chrp_init_IRQ(void)
 	chrp_find_openpic();
 	chrp_find_8259();
 
+#ifdef CONFIG_SMP
+	/* Pegasos has no MPIC, those ops would make it crash. It might be an
+	 * option to move setting them to after we probe the PIC though
+	 */
+	if (chrp_mpic != NULL)
+		smp_ops = &chrp_smp_ops;
+#endif /* CONFIG_SMP */
+
 	if (_chrp_type == _CHRP_Pegasos)
 		ppc_md.get_irq        = i8259_irq;