linux-kernel - Re: About irq_create_affinity_masks() for a platform device driver

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Date:   Mon, 3 Feb 2020 15:00:38 +0000
From:   John Garry <john.garry@...wei.com>
To:     Thomas Gleixner <tglx@...utronix.de>
CC:     Marc Zyngier <maz@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        chenxiang <chenxiang66@...ilicon.com>
Subject: Re: About irq_create_affinity_masks() for a platform device driver

Hi Thomas,

>>
>> 	pirqs = kzalloc(*count * sizeof(int), GFP_KERNEL);
>> 	if (!pirqs)
>> 		return -ENOMEM;
>>
>> 	dev->desc = irq_create_affinity_masks(*count, affd);
>> 	if (!dev->desc) {
>> 		kfree(irqs);
> 
> pirqs I assume and this also leaks the affinity masks and the pointer in
> dev.

Right

> 
>> 		return -ENOMEM;
>> 	}
>>
>> 	for (i = 0; i < *count; i++) {
>> 		pirqs[i] = platform_get_irq(dev, i);
>> 		if (irqs[i] < 0) {
>> 			kfree(dev->desc);
>> 			kfree(irqs);
>> 			return -ENOMEM;
> 
> That's obviously broken as well :)

Right, again

> 
>> 		}
>> 	}
>>
>> 	*irqs = pirqs;
>>
>> 	return 0;
>> }
>> EXPORT_SYMBOL_GPL(platform_get_irqs_affinity);

[...]

> 
> I wouldn't mind to expose a function which allows you to switch the
> allocated interrupts to managed. The reason why we do it in one go in
> the PCI code is that we get automatically the irq descriptors allocated
> on the correct node. So if the node aware allocation is not a
> showstopper 

I wouldn't say so for now.

for this then your function would do:
> 
> 	...
> 	for (i = 0; i < count; i++) {
> 		pirqs[i] = platform_get_irq(dev, i);
> 
>                  irq_update_affinity_desc(pirqs[i], affdescs + i);
> 
>          }
> 
> int irq_update_affinity_desc(unsigned int irq, irq_affinity_desc *affinity)
> {
> 	unsigned long flags;
> 	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, 0);
> 
>          if (!desc)
>          	return -EINVAL;
> 
>          if (affinity->is_managed) {
>          	irqd_set(&desc->irq_data, IRQD_IRQ_DISABLED);
> 	        irqd_set(&desc->irq_data, IRQD_IRQ_MASKED);

Are these correct? I assume we want to follow alloc_descs() here.

>          }
>          cpumask_copy(desc->irq_common_data.affinity, affinity);
>          return 0;
> }

I see. So I made a couple of changes and it did work:

int irq_update_affinity_desc(unsigned int irq, struct irq_affinity_desc 
*affinity)
{
	unsigned long flags;
	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, 0);

	if (!desc)
		return -EINVAL;

	if (affinity->is_managed) {
		irqd_set(&desc->irq_data, IRQD_AFFINITY_MANAGED);
		irqd_set(&desc->irq_data, IRQD_MANAGED_SHUTDOWN);
	}

	cpumask_copy(desc->irq_common_data.affinity, &affinity->mask);
	irq_put_desc_unlock(desc, flags);
	return 0;
}

And if we were to go this way, then we don't need to add the pointer in 
struct platform_device to hold affinity mask descriptors as we're using 
them immediately. Or even have a single function to do it all in the irq 
code (create the masks and update the affinity desc).

And since we're just updating the masks, I figure we shouldn't need to 
add acpi_irq_get_count(), which I invented to get the irq count (without 
creating the IRQ mapping).

Thanks,
John