linux-kernel - Re: [PATCH 1/3] ARM: at91/aic: add device tree support for AIC

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Message-ID: <4ED4D858.40506@atmel.com>
Date:	Tue, 29 Nov 2011 14:04:24 +0100
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	Jamie Iles <jamie@...ieiles.com>
CC:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/3] ARM: at91/aic: add device tree support for AIC

On 11/25/2011 04:28 PM, Jamie Iles :
> On Fri, Nov 25, 2011 at 02:51:06PM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
>> On 22:26 Thu 24 Nov     , Jamie Iles wrote:
>>> Hi Nicolas,
>>> On Thu, Nov 24, 2011 at 10:56:27PM +0100, Nicolas Ferre wrote:
> [...]
>>>> +#if defined(CONFIG_OF)
>>>> +static struct of_device_id aic_ids[]  = {
>>>> +	{ .compatible = "atmel,at91rm9200-aic" },
>>>> +	{ /*sentinel*/ }
>>>> +};
>>>> +
>>>> +static int __init at91_aic_of_init(void)
>>>> +{
>>>> +	struct device_node *np;
>>>> +
>>>> +	np = of_find_matching_node(NULL, aic_ids);
>>>> +	if (np == NULL)
>>>> +		return -ENODEV;
>>>> +
>>>> +	at91_aic_base = of_iomap(np, 0);
>>>> +	at91_aic_domain.of_node = np;
>>>
>>> I think this needs to be:
>>>
>>> 	at91_aic_domain.of_node = of_node_get(np);
>>>
>>> to keep the reference count.

Well, in fact the of_find_matching_node() function already indent the 
ref. count...

>>>> +	/* Keep refcount of the node */

... That is why I added this comment ^^

But maybe for sake of clarity, I may have used what you propose anyway. 
What it your opinion?

>>>> +
>>>> +	return 0;
>>>> +}
>>>> +#else
>>>> +static int __init at91_aic_of_init(void)
>>>> +{
>>>> +	return -ENOSYS;
>>>> +}
>>>> +#endif
>>>
>>> I think it's preferred if you use of_irq_init() here as it can handle
>>> the ordering of IRQ controllers.  There are GIC and VIC bindings in
>>> -next that use this and provide a way for non-DT platforms to still use
>>> the drivers.
>> which is the case here as if the of_init fail we failback to the non-dt init
>>
>> and this IP is AT91 only
>
> Right, but it's not using the of_irq_init() interface which is the
> standard way of registering interrupt controllers and will correctly
> dependencies for you.
>
> So if you could have something like:
>
> void __init __at91_aic_init(unsigned int priority[NR_AIC_IRQS],
> 			    void __iomem *regs,
> 			    struct device_node *np)
> {
> 	/*
> 	 * Do all of the writes to the AIC itself and configure
> 	 * the IRQ domain.
> 	 */
> }
>
> void __init at91_aic_init(unsigned int priority[NR_AIC_IRQS])
> {
> 	void __iomem *base = ioremap(AT91_AIC, 512);
>
> 	__at91_aic_init(priority, base, NULL);
> }
>
> int __init at91_aic_of_init(struct device_node *node,
> 			    struct device_node *parent)
> {
> 	void __iomem *regs = of_iomap(node, 0);
>
> 	/*
> 	 * Get priorities from the DT.  If this was an array of cells
> 	 * then that should be okay.
> 	 */
> 	__at91_aic_init(dt_priorities, regs, node);
> }
>
> Then the DT based board initialisation can do:
>
> static const struct of_device_id at91_irq_of_match[] __initconst = {
> 	{ .compatible = "atmel,at91-aic", .data = at91_aic_of_init },
> 	{}
> };
>
> static void __init at91_of_irq_init(void)
> {
> 	of_irq_init(at91_of_irq_init);
> }

That looks nice. I will try to implement this. I will try to figure out 
when of_irq_init() is called compared to the other init_IRQ() function.

> Which is consistent with other platforms.  However this does require
> that the priorities are encoded in the device-tree, but I guess that's a
> good thing anyway isn't it?

That is a annoying point: I do not want to add all this "default" 
priority stuff in the DT. It is kind of useless until we use the 
threaded interrupts everywhere and may bloat the DT...

I will try to find a way to pass the default priority table to the DT 
called function.

Thanks for your review,
-- 
Nicolas Ferre
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