linux-kernel - Re: [PATCH v4 1/2] Add the driver of mbigen interrupt controller

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Message-ID: <560960E9.6010302@arm.com>
Date:	Mon, 28 Sep 2015 16:46:49 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	"majun (F)" <majun258@...wei.com>
CC:	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Will Deacon <Will.Deacon@....com>,
	Mark Rutland <Mark.Rutland@....com>,
	"jason@...edaemon.net" <jason@...edaemon.net>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"lizefan@...wei.com" <lizefan@...wei.com>,
	"huxinwei@...wei.com" <huxinwei@...wei.com>,
	"dingtianhong@...wei.com" <dingtianhong@...wei.com>,
	"zhaojunhua@...ilicon.com" <zhaojunhua@...ilicon.com>,
	"liguozhu@...ilicon.com" <liguozhu@...ilicon.com>,
	"xuwei5@...ilicon.com" <xuwei5@...ilicon.com>,
	"wei.chenwei@...ilicon.com" <wei.chenwei@...ilicon.com>,
	"guohanjun@...wei.com" <guohanjun@...wei.com>,
	"wuyun.wu@...wei.com" <wuyun.wu@...wei.com>,
	"guodong.xu@...aro.org" <guodong.xu@...aro.org>,
	"haojian.zhuang@...aro.org" <haojian.zhuang@...aro.org>,
	"zhangfei.gao@...aro.org" <zhangfei.gao@...aro.org>,
	"usman.ahmad@...aro.org" <usman.ahmad@...aro.org>
Subject: Re: [PATCH v4 1/2] Add the driver of mbigen interrupt controller

On 25/09/15 12:56, majun (F) wrote:
> 
> 
> 在 2015/9/25 3:30, Marc Zyngier 写道:
>> On Wed, 23 Sep 2015 15:24:50 +0800
>> "majun (F)" <majun258@...wei.com> wrote:
>>
>> [...]
>>
>>>>> +static int mbigen_device_init(struct mbigen_chip *chip,
>>>>> +                       struct device_node *node)
> [...]
>>>>> +
>>>>> +core_initcall(mbigen_init);
>>>>
>>>> That's the wrong thing to do. The interrupt controller should be
>>>> probed with IRQCHIP_DECLARE(). Yes, this creates a dependency
>>>> problem between the MSI layer and the irqchip layer, but that
>>>> should be easy (-ish) to solve.
>>>
>>> Based on our discusstion about DTS,I will change the code likes below:
>>> IRQCHIP_DECLARE(hisi_mbigen, "hisilicon,mbigen-v2", mbigen_of_init);
>>>
>>> Mbigen device is initialized as a interrupt controller.
>>>
>>> But I still can't call platform_msi_domain_alloc_irqs()
>>> to apply the msi irqs.
>>>
>>> It think this is what you said "dependency problem between
>>>  the MSI layer and the irqchip layer" , am i right ?
>>>
>>> Do you have any idea about this problem?
>>
>> You need to have multiple phases for initializing this beast:
>> - IRQCHIP_DECLARE() to create the irqchips, allocate the domains and
>>   the main data structures,
>> - platform device probing of the top-level device to do some HW probing
>>   and to kick of_platform_populate on the subnodes,
>> - Handle the the subnode probing, allocate the MSIs, and finish the
>>   initialization of the irqchip how that you have all the information.
> 
> Ok, I got it. But I still have a question.
> According to your suggestions, the initial flow is:
> 
> Step1: IRQCHIP_DECLARE() to create the irqchips, allocate the domains and
> 	the main data structures,
> Step2: Parse the device node and apply the irq(named as *device-virq*) within mbigen-device	
> 	domain (handled by irq core code).
> Step3: platform device probing of the top-level device to do some HW probing
> 	and to kick of_platform_populate on the subnodes,
> Step4: Handle the the subnode probing, allocate the MSIs(named as *msi-virq*), and finish the
> 	initialization of the irqchip how that you have all the information.
> 
> My questions is:
> 	How to connect msi-virq and device-virq ?
> 
> In my v4 version, I used the
> 
> irq_set_chained_handler(msi-virq, mbigen_handle_cascade_irq);
> 
> as msi-virq primary handler function .
> 
> Then find  device-virq in mbigen_handle_cascade_irq()
> and call device-virq corresponding handler fucntion.
> 
> But it seems not a right solution.
> 
> So I want try another solution for this problem.
> 
> [1] In step2, when the interrupt controller map function is called, using
> 	irq_set_chip_and_handler(device-irq, &mbigen_irq_chip, handle_fasteoi_irq);
> [2] In step4, using
> 	for_each_msi_entry(desc, &mgn_dev->dev) {
> 		request_irq( msi-virq, msi_irq_handler, **);
> 	}
> 
> But I am not sure about this solution, please review this and offer me some suggestions.

I don't see what is wrong with keeping it as a chained irq handler.
Actually, you really need it to be a chained handler (because this is
what it is). So using irq_set_chained_handler_and_data() is probably the
right thing to do.

Thanks,

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