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

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Date:   Tue, 8 Feb 2022 15:31:52 +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 Tue, Feb 08, 2022 at 03:28:50PM +0000, Robin Murphy wrote:
> 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@...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 ;)
> 
> 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.

Next week is fine, no rush. I was just trying to work out what to do with
Lad's patches in this thread and it sounds like I should ignore them and
wait for your series instead.

Will