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

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Date:	Fri, 22 Jan 2016 17:37:35 +0100
From:	Marc Gonzalez <marc_gonzalez@...madesigns.com>
To:	Mans Rullgard <mans@...sr.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

On 22/01/2016 17:35, Måns Rullgård wrote:
> Marc Gonzalez <marc_gonzalez@...madesigns.com> writes:
> 
>> On 20/01/2016 19:09, Måns Rullgård wrote:
>>
>>> Marc Gonzalez <marc_gonzalez@...madesigns.com> writes:
>>>
>>>> On 20/01/2016 17:38, Måns Rullgård wrote:
>>>>
>>>>> 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.
>>>>
>>>> The two suggestions are over my head at the moment.
>>>>
>>>> Do you want to submit v4 and have Marc Z take a look?
>>>
>>> Done.  If this isn't acceptable either, I'm out of ideas that don't end
>>> up being far uglier than anything suggested so far.
>>
>> With your latest patch, can I drop the ranges property?
> 
> Why would you want to do that?

<confused> I thought that was the whole point of the v4 improvement?