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

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Message-ID: <20220208151932.GB1802@willie-the-truck>
Date:   Tue, 8 Feb 2022 15:19:32 +0000
From:   Will Deacon <will@...nel.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Joerg Roedel <joro@...tes.org>,
        Rob Clark <robdclark@...omium.org>,
        linux-arm-kernel@...ts.infradead.org,
        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>, linux-kernel@...r.kernel.org,
        Prabhakar <prabhakar.csengg@...il.com>
Subject: Re: [PATCH 1/2] iommu/arm-smmu: Use platform_irq_count() to get the
 interrupt count

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@...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.
> 
> 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 ;)

Will