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

[Robin Murphy]

On 2022-02-08 15:19, Will Deacon wrote:
> On Thu, Dec 23, 2021 at 02:14:35PM +0000, Robin Murphy wrote:
> > On 2021-12-23 13:00, Lad Prabhakar wrote:
> > > 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()
> >
> > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> > > ---
> > >    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.
> >
> > 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.
>
> Did you get anywhere with this? December 23rd is long forgotten by now ;)

Yup: 
https://gitlab.arm.com/linux-arm/linux-rm/-/commit/b2a40caaf1622eb35c555074a0d72f4f0513cff9

I'm still cleaning up the PMU driver that justifies the whole thing, but 
I can send that patch now if you reckon it's not complete nonsense out 
of context. Otherwise, I'll aim to get the whole lot out next week.


Cheers,
Robin.