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

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Date:	Fri, 22 Jan 2016 16:39:30 +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 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?

The point was to make it work right *if* someone were to do that even
though having it there better reflects what the hardware actually looks
like.

-- 
Måns Rullgård