linux-kernel - Re: [RFC PATCH v3] irqchip: Add support for Tango interrupt controller

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Date:	Wed, 20 Jan 2016 16:38:32 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Marc Gonzalez <marc_gonzalez@...madesigns.com>
Cc:	Marc Zyngier <marc.zyngier@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux ARM <linux-arm-kernel@...ts.infradead.org>,
	Sebastian Frias <sf84@...oste.net>
Subject: Re: [RFC PATCH v3] irqchip: Add support for Tango interrupt controller

Marc Gonzalez <marc_gonzalez@...madesigns.com> writes:

> On 20/01/2016 17:25, Måns Rullgård wrote:
>
>> Marc Zyngier <marc.zyngier@....com> writes:
>> 
>>> On 20/01/16 16:10, Måns Rullgård wrote:
>>>
>>>> Marc Zyngier <marc.zyngier@....com> writes:
>>>>
>>>>>> +	if (of_property_read_u32(node, "reg", &ctl))
>>>>>> +		panic("%s: failed to get reg base", node->name);
>>>>>> +
>>>>>> +	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
>>>>>> +	chip->ctl = ctl;
>>>>>> +	chip->base = base;
>>>>
>>>> As I said before, this assumes the outer DT node uses a ranges
>>>> property.  Normally reg properties work the same whether they specify an
>>>> offset within an outer "ranges" or have a full address directly.  It
>>>> would be easy enough to make this work with either, so I don't see any
>>>> reason not to.
>>>
>>> Yup, that is a good point. I guess Marc can address this in the next
>>> round, since we need a DT binding anyway.
>> 
>> I'd suggest using of_address_to_resource() on both nodes and subtracting
>> the start addresses returned.
>
> For my own reference, Marc Zyngier suggested:
> "you should use of_iomap to map the child nodes, and not mess with
> the parent one."

That's going to get very messy since the generic irqchip code needs all
the registers as offsets from a common base address.

-- 
Måns Rullgård