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Date:   Tue, 16 Feb 2021 12:00:32 +0100 (CET)
From:   Mark Kettenis <mark.kettenis@xs4all.nl>
To:     Arnd Bergmann <arnd@kernel.org>
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In-Reply-To: <CAK8P3a3rGurSQBubZ8i4+OHpDgM8mOfXiC6UhDYmL0MSQK4BRA@mail.gmail.com>
        (message from Arnd Bergmann on Tue, 16 Feb 2021 10:41:11 +0100)
Subject: Re: [PATCH v2 14/25] dt-bindings: interrupt-controller: Add DT
 bindings for apple-aic
References: <20210215121713.57687-1-marcan@marcan.st> <20210215121713.57687-15-marcan@marcan.st> <CAK8P3a3rGurSQBubZ8i4+OHpDgM8mOfXiC6UhDYmL0MSQK4BRA@mail.gmail.com>
Message-ID: <c1bc451789d233df@bloch.sibelius.xs4all.nl>
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> 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 <marcan@marcan.st> wrote:
> > +
> > +      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?