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>

arch/powerpc/include/asm/mpic.h

@@ -355,6 +355,8 @@ struct mpic
 #define MPIC_NO_BIAS			0x00000400
 /* Ignore NIRQS as reported by FRR */
 #define MPIC_BROKEN_FRR_NIRQS		0x00000800
+/* Destination only supports a single CPU at a time */
+#define MPIC_SINGLE_DEST_CPU		0x00001000
 
 /* MPIC HW modification ID */
 #define MPIC_REGSET_MASK		0xf0000000

arch/powerpc/platforms/85xx/mpc85xx_ds.c

@@ -78,7 +78,8 @@ void __init mpc85xx_ds_pic_init(void)
 
 	mpic = mpic_alloc(np, r.start,
 			  MPIC_PRIMARY | MPIC_WANTS_RESET |
-			  MPIC_BIG_ENDIAN | MPIC_BROKEN_FRR_NIRQS,
+			  MPIC_BIG_ENDIAN | MPIC_BROKEN_FRR_NIRQS |
+			  MPIC_SINGLE_DEST_CPU,
 			0, 256, " OpenPIC  ");
 	BUG_ON(mpic == NULL);
 	of_node_put(np);

arch/powerpc/platforms/86xx/pic.c

@@ -44,7 +44,8 @@ void __init mpc86xx_init_irq(void)
 
 	mpic = mpic_alloc(np, res.start,
 			MPIC_PRIMARY | MPIC_WANTS_RESET |
-			MPIC_BIG_ENDIAN | MPIC_BROKEN_FRR_NIRQS,
+			MPIC_BIG_ENDIAN | MPIC_BROKEN_FRR_NIRQS |
+			MPIC_SINGLE_DEST_CPU,
 			0, 256, " MPIC     ");
 	of_node_put(np);
 	BUG_ON(mpic == NULL);

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)