Re: Affinity for GIC irq line

From: Marc Zyngier
Date: Wed Apr 25 2018 - 03:07:41 EST

On 25/04/18 04:23, valmiki wrote:
> Hi all,
> When an IRQ line is set affinity using irq_set_affinity, which calls
> irq_do_set_affinity, this API copies affinity mask to affinity variable
> in irq_common_data of this irq descriptor.

It does a wee bit more. Crucially, it contains the line:

ret = chip->irq_set_affinity(data, mask, force);

> But as per ARM GICv2 document in order to drive a interrupt to a
> specific CPU we need to program GICD_ITARGETSRn register.
> But irq_set_affinity isn't writing to this register.Please correct me if
> I'm wrong i did not find code for this register being updated in
> irq_set_affinity flow.
> So how affinity is being set for an IRQ line ?

I would have though that a function name such as "gic_set_affinity" was
clear enough?

> If affinity was set successfully on what CPU does asm_do_IRQ run ?

It runs on the CPU that the interrupt targets, I'd say.

Jazz is not dead. It just smells funny...