Re: [PATCH 1/2] iommu/arm-smmu: Use platform_irq_count() to get the interrupt count

Hi Robin,

Thank you for the review.

On Thu, Dec 23, 2021 at 2:14 PM Robin Murphy [off-list ref] wrote:

On 2021-12-23 13:00, Lad Prabhakar wrote:

quoted

platform_get_resource(pdev, IORESOURCE_IRQ, ..) relies on static
allocation of IRQ resources in DT core code, this causes an issue
when using hierarchical interrupt domains using "interrupts" property
in the node as this bypasses the hierarchical setup and messes up the
irq chaining.

In preparation for removal of static setup of IRQ resource from DT core
code use platform_get_irq_count().

Nit: platform_irq_count()

quoted

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
---
  drivers/iommu/arm/arm-smmu/arm-smmu.c | 12 ++++++------
  1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 4bc75c4ce402..4844cd075644 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c

@@ -2105,12 +2105,12 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
      if (IS_ERR(smmu))
              return PTR_ERR(smmu);

-     num_irqs = 0;
-     while ((res = platform_get_resource(pdev, IORESOURCE_IRQ, num_irqs))) {
-             num_irqs++;
-             if (num_irqs > smmu->num_global_irqs)
-                     smmu->num_context_irqs++;
-     }
+     num_irqs = platform_irq_count(pdev);
+     if (num_irqs < 0)
+             return num_irqs;
+
+     if (num_irqs > smmu->num_global_irqs)
+             smmu->num_context_irqs += (num_irqs - smmu->num_global_irqs);

This seems a bit overcomplicated. I reckon:

        smmu->num_context_irqs = num_irqs - smmu->num_global_irqs;
        if (num_irqs <= smmu->num_global_irqs) {
                dev_err(...

should do it.

Agreed.

However, FYI I have some patches refactoring most of the IRQ stuff here
that I plan to post next cycle (didn't quite have time to get them done
for 5.17 as I'd hoped...), so unless this needs to go in right now as an
urgent fix, I'm happy to take care of removing platform_get_resource()
as part of that if it's easier.

Fine by me, let me know if it gets any later than planned I'll send a v2.

Cheers,
Prabhakar

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