Re: [PATCH v2 14/25] dt-bindings: interrupt-controller: Add DT bindings for apple-aic

From: Arnd Bergmann <arnd@kernel.org>
Date: Tue, 16 Feb 2021 10:41:11 +0100

On Mon, Feb 15, 2021 at 1:17 PM Hector Martin [off-list ref] wrote:

quoted

+
+      The 2nd cell contains the interrupt number.
+        - HW IRQs: interrupt number
+        - FIQs:
+          - 0: physical HV timer
+          - 1: virtual HV timer
+          - 2: physical guest timer
+          - 3: virtual guest timer

I wonder if you could just model the FIQ as a single shared level interrupt
(which is essentially what it is), and have every driver that uses it do a
request_irq() on the same IRQ number.

This would avoid having to come up with a fake binding for it, and simplify
the implementation that then no longer has to peek into each interrupt
source.

That would tie the binding more closely to the implementation as it
would remove the option of peeking at the interrupt source.  And
wouldn't it mean that the arch_timer driver would need to know whether
the interrupt is shared or not?