linux-kernel - Re: [PATCH v5 05/10] dt-bindings: irqchip: Introduce TISCI Interrupt router bindings

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Date:   Wed, 20 Feb 2019 08:36:51 -0800
From:   Tony Lindgren <tony@...mide.com>
To:     Lokesh Vutla <lokeshvutla@...com>
Cc:     Nishanth Menon <nm@...com>,
        Device Tree Mailing List <devicetree@...r.kernel.org>,
        jason@...edaemon.net, Peter Ujfalusi <peter.ujfalusi@...com>,
        marc.zyngier@....com, 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>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v5 05/10] dt-bindings: irqchip: Introduce TISCI Interrupt
 router bindings

Hi,

Some more info on chained irq vs mux below that might
help.

* Tony Lindgren <tony@...mide.com> [190219 15:36]:
> * Lokesh Vutla <lokeshvutla@...com> [190219 08:51]:
> > With this can you tell me how can we not have a device-tree and still support
> > irq allocation?
> 
> Using standard dts reg property to differentiate the interrupt
> router instances. And if the interrupt router is a mux, you should
> treat it as a mux rather than a chained interrupt controller.
> 
> We do have drivers/mux nowadays, not sure if it helps in this case
> as at least timer interrupts need to be configured very early.

Adding Linus Walleij to Cc since he posted a good test to
consider if something should use chained (or nested) irq:

"individual masking and ACKing bits and can all be used at the
 same time" [0]

Not sure if we have that documented somewhere?

But seems like the interrupt router should be set up as
a separate mux driver talking with firmware that the
interrupt controller driver calls on request_irq()?

Cheers,

Tony


[0] https://marc.info/?l=linux-omap&m=155065629529311&w=2