drivers/perf: arm_pmu: Fix NULL pointer dereference during probe

Patch 7f1d642 ("drivers/perf: arm-pmu: Fix handling of SPI lacking
interrupt-affinity property") unintended also fixes perf_event support
for bcm2835 which doesn't have PMU interrupts. Unfortunately this change
introduce a NULL pointer dereference on bcm2835, because irq_is_percpu
always expected to be called with a valid IRQ. So fix this regression
by validating the IRQ before.

Tested-by: Kevin Hilman <[email protected]>
Signed-off-by: Stefan Wahren <[email protected]>
Fixes: 7f1d642 ("drivers/perf: arm-pmu: Fix handling of SPI lacking "interrupt-affinity" property")
Signed-off-by: Will Deacon <[email protected]>
Signed-off-by: Catalin Marinas <[email protected]>

drivers/perf/arm_pmu.c

@@ -970,7 +970,7 @@ static int of_pmu_irq_cfg(struct arm_pmu *pmu)
 	if (cpumask_weight(&pmu->supported_cpus) == 0) {
 		int irq = platform_get_irq(pdev, 0);
 
-		if (irq_is_percpu(irq)) {
+		if (irq >= 0 && irq_is_percpu(irq)) {
 			/* If using PPIs, check the affinity of the partition */
 			int ret;