powerpc/mpic: Fix regression caused by change of default IRQ affinity

The Freescale implementation of MPIC only allows a single CPU destination
for non-IPI interrupts.  We add a flag to the mpic_init to distinquish
these variants of MPIC.  We pull in the irq_choose_cpu from sparc64 to
select a single CPU as the destination of the interrupt.

This is to deal with the fact that the default smp affinity was
changed by commit 18404756765c713a0be4eb1082920c04822ce588 ("genirq:
Expose default irq affinity mask (take 3)") to be all CPUs.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 55 insertions, 4 deletions

diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index 8e3478c995ef..f6299cca7814 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -563,6 +563,51 @@ static void __init mpic_scan_ht_pics(struct mpic *mpic)
 
 #endif /* CONFIG_MPIC_U3_HT_IRQS */
 
+#ifdef CONFIG_SMP
+static int irq_choose_cpu(unsigned int virt_irq)
+{
+        cpumask_t mask = irq_desc[virt_irq].affinity;
+        int cpuid;
+
+        if (cpus_equal(mask, CPU_MASK_ALL)) {
+                static int irq_rover;
+                static DEFINE_SPINLOCK(irq_rover_lock);
+                unsigned long flags;
+
+                /* Round-robin distribution... */
+        do_round_robin:
+                spin_lock_irqsave(&irq_rover_lock, flags);
+
+                while (!cpu_online(irq_rover)) {
+                        if (++irq_rover >= NR_CPUS)
+                                irq_rover = 0;
+                }
+                cpuid = irq_rover;
+                do {
+                        if (++irq_rover >= NR_CPUS)
+                                irq_rover = 0;
+                } while (!cpu_online(irq_rover));
+
+                spin_unlock_irqrestore(&irq_rover_lock, flags);
+        } else {
+                cpumask_t tmp;
+
+                cpus_and(tmp, cpu_online_map, mask);
+
+                if (cpus_empty(tmp))
+                        goto do_round_robin;
+
+                cpuid = first_cpu(tmp);
+        }
+
+        return cpuid;
+}
+#else
+static int irq_choose_cpu(unsigned int virt_irq)
+{
+        return hard_smp_processor_id();
+}
+#endif
 
 #define mpic_irq_to_hw(virq)    ((unsigned int)irq_map[virq].hwirq)
 
@@ -777,12 +822,18 @@ void mpic_set_affinity(unsigned int irq, cpumask_t cpumask)
         struct mpic *mpic = mpic_from_irq(irq);
         unsigned int src = mpic_irq_to_hw(irq);
 
-        cpumask_t tmp;
+        if (mpic->flags & MPIC_SINGLE_DEST_CPU) {
+                int cpuid = irq_choose_cpu(irq);
 
-        cpus_and(tmp, cpumask, cpu_online_map);
+                mpic_irq_write(src, MPIC_INFO(IRQ_DESTINATION), 1 << cpuid);
+        } else {
+                cpumask_t tmp;
 
-        mpic_irq_write(src, MPIC_INFO(IRQ_DESTINATION),
-                       mpic_physmask(cpus_addr(tmp)[0]));       
+                cpus_and(tmp, cpumask, cpu_online_map);
+
+                mpic_irq_write(src, MPIC_INFO(IRQ_DESTINATION),
+                               mpic_physmask(cpus_addr(tmp)[0]));
+        }
 }
 
 static unsigned int mpic_type_to_vecpri(struct mpic *mpic, unsigned int type)