linux-kernel - Re: [PATCH v2 09/10] irqchip: ti-sci-inta: Add support for Interrupt Aggregator driver

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Message-ID: <86bm792mv2.wl-marc.zyngier@arm.com>
Date:   Thu, 01 Nov 2018 09:00:49 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     Lokesh Vutla <lokeshvutla@...com>, Nishanth Menon <nm@...com>,
        Device Tree Mailing List <devicetree@...r.kernel.org>,
        Grygorii Strashko <grygorii.strashko@...com>,
        <jason@...edaemon.net>, Sekhar Nori <nsekhar@...com>,
        <linux-kernel@...r.kernel.org>, Tero Kristo <t-kristo@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Santosh Shilimkar <ssantosh@...nel.org>, <tglx@...utronix.de>,
        Linux ARM Mailing List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 09/10] irqchip: ti-sci-inta: Add support for Interrupt Aggregator driver

On Thu, 01 Nov 2018 07:55:12 +0000,
Peter Ujfalusi <peter.ujfalusi@...com> wrote:
> 
> Lokesh,
> 
> On 10/29/18 3:04 PM, Lokesh Vutla wrote:
> >>> With the above information, linux should send a message to
> >>> system-controller using TISCI protocol. After policing the given
> >>> information, system-controller does the following:
> >>> - Attaches the interrupt(INTA input) to the device resource index
> >>> - Muxes the interrupt(INTA input) to corresponding vint(INTA output)
> >>> - Muxes the vint(INTR input) to GIC irq(INTR output).
> >>
> >> Isn't there a 1:1 mapping between *used* INTR inputs and outputs?
> >> Since INTR is a router, there is no real muxing. I assume that the
> >> third point above is just a copy-paste error.
> > 
> > Right, my bad. INTR is just a router and no read muxing.
> 
> INTR can mux M interrupt inputs to N interrupt outputs.
> One selects which interrupt input is outputted on the given interrupt
> output.
> It is perfectly valid (but not sane) to select the same interrupt input
> to be routed to _all_ interrupt output for example.
> 
> Not sure if we are going to use this for anything but 1:1 mapping, but
> might worth keeping in mind...

It's not obvious how you'd use this "feature". Interrupt replicator,
should one of the output be tied to another part of the system? Or
maybe that's just the result of reusing some generic block...

	M.

-- 
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