Re: About irq_create_affinity_masks() for a platform device driver

From: Thomas Gleixner
Date: Tue Feb 04 2020 - 04:20:34 EST


John,

John Garry <john.garry@xxxxxxxxxx> writes:
>> 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.

Good.

> 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.

Yeah, copied the wrong chunk :)

>> }
>> 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;
> }

Looks correct.

> 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).

Yes, you can create and apply the masks after setting up the interrupts.

Thanks,

tglx