[PATCH] ARM: pmu: avoid setting IRQ affinity on UP systems

[PATCH] ARM: pmu: avoid setting IRQ affinity on UP systems

[Will Deacon]

Now that we can execute a CONFIG_SMP kernel on a uniprocessor system,
extra care has to be taken in the PMU IRQ affinity setting code to
ensure that we don't always fail to initialise.

This patch changes the CPU PMU initialisation code so that when we
only have a single IRQ, whose affinity can not be changed at the
controller, we report success (0) rather than -EINVAL.

Cc: Jamie Iles <jamie@jamieiles.com>
Reported-by: Avik Sil <avik.sil@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm/kernel/pmu.c |   21 ++++++++++++++-------
 1 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/arch/arm/kernel/pmu.c b/arch/arm/kernel/pmu.c
index b8af96e..2b65d10 100644
--- a/arch/arm/kernel/pmu.c
+++ b/arch/arm/kernel/pmu.c
@@ -97,22 +97,29 @@ set_irq_affinity(int irq,
 			   irq, cpu);
 	return err;
 #else
-	return 0;
+	return -EINVAL;
 #endif
 }
 
 static int
 init_cpu_pmu(void)
 {
-	int i, err = 0;
+	int i, irqs, err = 0;
 	struct platform_device *pdev = pmu_devices[ARM_PMU_DEVICE_CPU];
 
-	if (!pdev) {
-		err = -ENODEV;
-		goto out;
-	}
+	if (!pdev)
+		return -ENODEV;
+
+	irqs = pdev->num_resources;
+
+	/*
+	 * If we have a single PMU interrupt that we can't shift, assume that
+	 * we're running on a uniprocessor machine and continue.
+	 */
+	if (irqs == 1 && !irq_can_set_affinity(platform_get_irq(pdev, 0)))
+		return 0;
 
-	for (i = 0; i < pdev->num_resources; ++i) {
+	for (i = 0; i < irqs; ++i) {
 		err = set_irq_affinity(platform_get_irq(pdev, i), i);
 		if (err)
 			break;
-- 
1.7.0.4

[PATCH] ARM: pmu: avoid setting IRQ affinity on UP systems

[Jamie Iles]

On Tue, Feb 15, 2011 at 12:11:39PM +0000, Will Deacon wrote:
> Now that we can execute a CONFIG_SMP kernel on a uniprocessor system,
> extra care has to be taken in the PMU IRQ affinity setting code to
> ensure that we don't always fail to initialise.
> 
> This patch changes the CPU PMU initialisation code so that when we
> only have a single IRQ, whose affinity can not be changed at the
> controller, we report success (0) rather than -EINVAL.
> 
> Cc: Jamie Iles <jamie@jamieiles.com>
> Reported-by: Avik Sil <avik.sil@linaro.org>
> Signed-off-by: Will Deacon <will.deacon@arm.com>

Look good!

Acked-by: Jamie Iles <jamie@jamieiles.com>

Jamie

[PATCH] ARM: pmu: avoid setting IRQ affinity on UP systems

[Will Deacon]

Hi Jamie,

> On Tue, Feb 15, 2011 at 12:11:39PM +0000, Will Deacon wrote:
> > Now that we can execute a CONFIG_SMP kernel on a uniprocessor system,
> > extra care has to be taken in the PMU IRQ affinity setting code to
> > ensure that we don't always fail to initialise.
> >
> > This patch changes the CPU PMU initialisation code so that when we
> > only have a single IRQ, whose affinity can not be changed at the
> > controller, we report success (0) rather than -EINVAL.
> >
> > Cc: Jamie Iles <jamie@jamieiles.com>
> > Reported-by: Avik Sil <avik.sil@linaro.org>
> > Signed-off-by: Will Deacon <will.deacon@arm.com>
> 
> Look good!
> 
> Acked-by: Jamie Iles <jamie@jamieiles.com>

Cheers. I've submitted this as 6742/1 with a minor change (deleted the out:
label as it's no longer used).

Will