linux-kernel - Re: [RFC PATCH v2] irqchip: Add support for tango interrupt router

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Date:   Sun, 16 Jul 2017 01:46:58 +0200
From:   Mason <slash.tmp@...e.fr>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Mark Rutland <mark.rutland@....com>,
        Thibaud Cornic <thibaud_cornic@...madesigns.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH v2] irqchip: Add support for tango interrupt router

On 15/07/2017 15:06, Mason wrote:

> I have two remaining issues:
> 
> 1) In the ISR, I get the hwirq from the GIC. What is the
> API to translate that to the SPI? I'm currently just
> subtracting 32.

gic_set_type() in drivers/irqchip/irq-gic.c

	/* SPIs have restrictions on the supported types */
	if (gicirq >= 32 && type != IRQ_TYPE_LEVEL_HIGH &&
			    type != IRQ_TYPE_EDGE_RISING)
		return -EINVAL;


gic_irq_domain_translate() in the same file:

		/* Get the interrupt number and add 16 to skip over SGIs */
		*hwirq = fwspec->param[1] + 16;

		/*
		 * For SPIs, we need to add 16 more to get the GIC irq
		 * ID number
		 */
		if (!fwspec->param[0])
			*hwirq += 16;


So it seems "acceptable" to compute spi = d->hwirq - 32;


> 2) I'm currently using a single domain, with a
> handle_simple_irq domain handler. That's probably
> wrong. Should I define two domains, one for edge
> IRQs and one for level IRQs, and use the appropriate
> handler?  Should both domain have 128 entries?
> (I.e. are they indexed by the hwirq?)
> And should I use linear or tree?

I will read this again carefully:
https://www.kernel.org/doc/Documentation/IRQ-domain.txt

Regards.