linux-kernel - Re: [PATCH v3 1/2] irqchip: Add driver for Loongson-1 interrupt controller

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Message-ID: <868sz78vtd.wl-marc.zyngier@arm.com>
Date:   Sat, 26 Jan 2019 12:09:18 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Jiaxun Yang <jiaxun.yang@...goat.com>
Cc:     linux-mips@...r.kernel.org, tglx@...utronix.de,
        jason@...edaemon.net, robh+dt@...nel.org, mark.rutland@....com,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 1/2] irqchip: Add driver for Loongson-1 interrupt controller

On Fri, 25 Jan 2019 10:56:33 +0000,
Jiaxun Yang <jiaxun.yang@...goat.com> wrote:
> 
> Hi Marc
> 
> Thanks for your suggestions, I'm working on v4 and I would like to
> ask if it is better to have a driver for only one irqchip and create
> dt nodes for each chip, or just register all the chips in a single
> driver with only one dt node.

It would make more sense to have a node per chip, meaning that you
end-up with one instance per chip as well. It won't make the driver
much more complicated.

[...]

> >> +	domain = irq_domain_add_legacy(node, num_chips * 32, LS1X_IRQ_BASE, 0,
> >> +		&irq_domain_simple_ops, NULL);
> > Why a legacy domain? This is usually reserved to old drivers that are
> > converted to a new infrastructure, while needing some form of platform
> > hacks. I don't see this being the case here.
> > 
> > It is also worrying that although you have up to 5 irqchips, they all
> > share a single domain. What does this mean? each irqchip is expected
> > to have its own domain.
> 
> Yes, I do like this for backward compatible reason. I'm turning
> a legacy platform device mach(arch/mips/loongson32) in to
> dt based generic mach and I would like to do it step by step rather
> than one time.
> 
> So I use legacy domain in order to keep IRQ same with the
> old driver exist on arch/mips/loongson32/common/irq.c

OK, it would have been good to make a note of that in the cover
letter, which is a bit empty at the moment.

Thanks,

	M.

-- 
Jazz is not dead, it just smell funny.