linux-kernel - Re: [RFC v2 PATCH 07/14] irq: add a new generic IPI reservation code to irq core

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Message-ID: <5631F770.3040702@imgtec.com>
Date:	Thu, 29 Oct 2015 10:39:44 +0000
From:	Qais Yousef <qais.yousef@...tec.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	<linux-kernel@...r.kernel.org>, <jason@...edaemon.net>,
	<marc.zyngier@....com>, <jiang.liu@...ux.intel.com>,
	<ralf@...ux-mips.org>, <linux-mips@...ux-mips.org>
Subject: Re: [RFC v2 PATCH 07/14] irq: add a new generic IPI reservation code
 to irq core

On 10/28/2015 03:46 PM, Qais Yousef wrote:
> Hi Thomas,
>
> On 10/13/2015 03:38 PM, Qais Yousef wrote:
>> On 10/13/2015 02:37 PM, Thomas Gleixner wrote:
>>> On Tue, 13 Oct 2015, Qais Yousef wrote:
>>>
>>>> +    if (domain == NULL)
>>>> +        domain = irq_default_domain; /* need a separate 
>>>> ipi_default_domain? */
>>> No tail comments please.
>>>
>>> We should neither use irq_default_domain nor have an
>>> ipi_default_domain.
>>
>> OK though I understood that you were OK with using the 
>> irq_default_domain.
>>
>> This means that arch code must parse the DT for an IPI domain. I 
>> think I've seen arch code using the root FDT to search for a specific 
>> node. I'll try to do something similar to search for an IPI domain.
>
> I'm having an issue here. I made the arch code look for an IPI domain 
> but we have some platforms on MIPS that don't support device tree. I 
> can't find how I can go away with that without using irq_default_domain.
>
> Also irq_default_domain is understandably only visible within 
> irqdomain code, so I can't make the arch code fallback to passing 
> irq_default_domain if the platform doesn't support DT.
>
> Are you OK with keeping this in irq_reserve_ipi()? Alternatively I 
> could modify irq_find_host(), which I'm using to find the IPI domain, 
> return irq_default_domain() if the passed node is NULL.
>
> Or maybe there's a better option I couldn't think of?

I think I can fix this in the GIC driver by using my own 
irq_domain->ops->match() function to ignore when of_node is NULL to cope 
with platforms without DT.

Sorry for the noise.

Thanks,
Qais
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