Subject: Re: [PATCH 0/5] firmware/irqchip: Add FF-A DT interrupt support for donated NS SGIs

From: Marc Zyngier <[email-masked]>
Date: Wed, 22 Apr 2026 12:01:16 +0100

On Sun, 12 Apr 2026 18:04:36 +0100,
Sudeep Holla <[email-masked]> wrote:
> 
> Hi all,
> 
> This series wires FF-A notification interrupts up through DT using the
> standard interrupts property on the arm,ffa node and adds the
> required GICv3 and binding support for secure-donated non-secure SGIs.
> 
> This has been long pending after the discussions here[1][2]. I have been
> waiting for some ACPI story to shape up for almost an year now, but no
> progress there. So posting this for now to start discussion on the approach
> taken here instead of waiting for another year to sort out ACPI 😉.
> 
> It:
> 
> - documents secure-donated NS SGIs in the GIC DT binding
> - teaches the GICv3 driver to accept and map those SGIs
> - adds a DT binding for the arm,ffa firmware node
> - updates the FF-A driver to use the arm,ffa node interrupt instead of
>   synthesizing its own GIC mapping
> - adds an FVP DT node using SGI 8 as the FF-A notification interrupt
>
> The FF-A DT lookup expects a single interrupt entry, verifies that it is
> a per-CPU interrupt via the reported affinity mask, and cross-checks the
> resolved Linux IRQ hwirq against the interrupt ID returned by
> FFA_FEATURES.

I haven't looked at this in any detail, but these are the additional
issues someone needs to address:

- The GIC(v3) is dead, long live the GIC(v5)! SGIs don't exist in the
  brave new world, so FFA needs to find new ways to signal interrupts.

- FFA doesn't necessarily live in secure world, and could be
  implemented by a hypervisor. In the context of a single security
  domain machine (that's what a VM is), the guest *owns* all SGIs. So
  there is absolutely nothing to donate, and this doesn't work. FFA
  also needs fixing here.

- All of the above should work with the other firmware description
  (Avoid Critical Periodic Interrupts). But maybe FFA is not a thing
  on these machines? If not, it should be made explicit.

Overall, it only indicates that FFA should behave as a device, and
use interrupts that are valid for a device.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.