powerpc: Add accounting for Doorbell interrupts

This patch adds a new line to /proc/interrupts to account for the
doorbell interrupts that each hardware thread has received. The total
interrupt count in /proc/stat will now also include doorbells.

 # cat /proc/interrupts
           CPU0       CPU1       CPU2       CPU3
 16:        551       1267        281        175      XICS Level     IPI
LOC:       2037       1503       1688       1625   Local timer interrupts
SPU:          0          0          0          0   Spurious interrupts
CNT:          0          0          0          0   Performance monitoring interrupts
MCE:          0          0          0          0   Machine check exceptions
DBL:         42        550         20         91   Doorbell interrupts

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>

arch/powerpc/include/asm/hardirq.h

@@ -10,6 +10,9 @@ typedef struct {
 	unsigned int pmu_irqs;
 	unsigned int mce_exceptions;
 	unsigned int spurious_irqs;
+#ifdef CONFIG_PPC_DOORBELL
+	unsigned int doorbell_irqs;
+#endif
 } ____cacheline_aligned irq_cpustat_t;
 
 DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);

arch/powerpc/kernel/dbell.c

@@ -41,6 +41,8 @@ void doorbell_exception(struct pt_regs *regs)
 
 	may_hard_irq_enable();
 
+	__get_cpu_var(irq_stat).doorbell_irqs++;
+
 	smp_ipi_demux();
 
 	irq_exit();

arch/powerpc/kernel/irq.c

@@ -374,6 +374,15 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 		seq_printf(p, "%10u ", per_cpu(irq_stat, j).mce_exceptions);
 	seq_printf(p, "  Machine check exceptions\n");
 
+#ifdef CONFIG_PPC_DOORBELL
+	if (cpu_has_feature(CPU_FTR_DBELL)) {
+		seq_printf(p, "%*s: ", prec, "DBL");
+		for_each_online_cpu(j)
+			seq_printf(p, "%10u ", per_cpu(irq_stat, j).doorbell_irqs);
+		seq_printf(p, "  Doorbell interrupts\n");
+	}
+#endif
+
 	return 0;
 }
 
@@ -387,6 +396,9 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
 	sum += per_cpu(irq_stat, cpu).pmu_irqs;
 	sum += per_cpu(irq_stat, cpu).mce_exceptions;
 	sum += per_cpu(irq_stat, cpu).spurious_irqs;
+#ifdef CONFIG_PPC_DOORBELL
+	sum += per_cpu(irq_stat, cpu).doorbell_irqs;
+#endif
 
 	return sum;
 }