linux-kernel - Re: [PATCH v2 6/9] irqchip / gic: Add stacked irqdomain support for ACPI based GICv2 init

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Message-ID: <55910440.8070702@arm.com>
Date:	Mon, 29 Jun 2015 09:39:28 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Hanjun Guo <hanjun.guo@...aro.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>
CC:	Jason Cooper <jason@...edaemon.net>,
	Will Deacon <Will.Deacon@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Olof Johansson <olof@...om.net>, Wei Huang <wei@...hat.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>
Subject: Re: [PATCH v2 6/9] irqchip / gic: Add stacked irqdomain support for
 ACPI based GICv2 init

On 27/06/15 04:52, Hanjun Guo wrote:
> On 06/24/2015 01:38 AM, Lorenzo Pieralisi wrote:
>> On Tue, Jun 23, 2015 at 04:11:38PM +0100, Hanjun Guo wrote:
>>
>> [...]
>>
>>>>> diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
>>>>> index 8fc67bc..d1b2131 100644
>>>>> --- a/drivers/irqchip/irq-gic.c
>>>>> +++ b/drivers/irqchip/irq-gic.c
>>>>> @@ -851,15 +851,22 @@ static struct notifier_block gic_cpu_notifier = {
>>>>>    static int gic_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
>>>>>    				unsigned int nr_irqs, void *arg)
>>>>>    {
>>>>> -	int i, ret;
>>>>> +	int i;
>>>>>    	irq_hw_number_t hwirq;
>>>>> -	unsigned int type = IRQ_TYPE_NONE;
>>>>> -	struct of_phandle_args *irq_data = arg;
>>>>>
>>>>> -	ret = gic_irq_domain_xlate(domain, irq_data->np, irq_data->args,
>>>>> -				   irq_data->args_count, &hwirq, &type);
>>>>> -	if (ret)
>>>>> -		return ret;
>>>>> +	if (domain->of_node) {	/* DT case */
>>>>> +		int ret;
>>>>> +		unsigned int type = IRQ_TYPE_NONE;
>>>>> +		struct of_phandle_args *irq_data = arg;
>>>>> +
>>>>> +		ret = gic_irq_domain_xlate(domain, irq_data->np,
>>>>> +					irq_data->args,
>>>>> +					irq_data->args_count, &hwirq, &type);
>>>>> +		if (ret)
>>>>> +			return ret;
>>>>> +	} else {	/* ACPI case */
>>>>> +		hwirq = (irq_hw_number_t)*(u32 *)arg;
>>>>> +	}
>>>>
>>>> If domain->of_node is NULL and system booted with DT the code above
>>>> does not fail (and if it fails almost certainly that won't be graceful)
>>>> but it should.
>>>
>>> how about the following logic?
>>>
>>> if (!domain->of_node && acpi_disabled)
>>> 	return -ENODEV;
>>> else if (domain->of_node)
>>> 	dt related code;
>>> else
>>> 	ACPI related code;
>>
>> Code is not checking the node at present so:
>>
>> if (acpi_disabled)
>> 	dt code;
>> else
>> 	ACPI code;
>>
>> would do, but that's a nit.
>>
>>>>>    	for (i = 0; i < nr_irqs; i++)
>>>>>    		gic_irq_domain_map(domain, virq + i, hwirq + i);
>>>>> @@ -945,11 +952,11 @@ void __init gic_init_bases(unsigned int gic_nr, int irq_start,
>>>>>    		gic_irqs = 1020;
>>>>>    	gic->gic_irqs = gic_irqs;
>>>>>
>>>>> -	if (node) {		/* DT case */
>>>>> +	if (node || !acpi_disabled) {		/* DT or ACPI case */
>>>>>    		gic->domain = irq_domain_add_linear(node, gic_irqs,
>>>>>    						    &gic_irq_domain_hierarchy_ops,
>>>>>    						    gic);
>>
>> I think this is a bit more worrying, I mean passing a NULL node pointer to
>> the irqdomain layer which basically means you are booting out of ACPI
> 
> I'm little confused here, would you mind explaining more for your
> worrying? To me, node pointer is optional and it's ok for ACPI
> case.
> 
>> (for you, if that's true for the irq_domain_add_linear implementation
>> that's another story), the node pointer should be optional but you
>> need feedback from IRQ layer maintainers here.
> 
> Sure.

Frankly, I'd really like to see ACPI using the "node" parameter for
something useful. This would save having to cache pointers all over the
place, will make find_irq_host() work as expected... etc.

See the comment at the top of linux/irqdomain.h :

"... This code could thus be used on other architectures by replacing
those two by some sort of arch-specific void * "token" used to identify
interrupt controllers."

Maybe it is time to bite the bullet.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...
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