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

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Date:   Tue, 8 Feb 2022 15:28:50 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Will Deacon <will@...nel.org>
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 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.


Cheers,
Robin.