linux-kernel - Re: [PATCH 1/2] iommu/arm-smmu: Use platform_irq

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Date:   Thu, 23 Dec 2021 17:36:56 +0000
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Will Deacon <will@...nel.org>, Joerg Roedel <joro@...tes.org>,
        Rob Clark <robdclark@...omium.org>,
        LAK <linux-arm-kernel@...ts.infradead.org>,
        Linux IOMMU <iommu@...ts.linux-foundation.org>,
        Xin Tan <tanxin.ctf@...il.com>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        "Isaac J. Manjarres" <isaacm@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: 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 <robin.murphy@....com> 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@...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