linux-kernel - Re: [PATCH v5 1/3] initialize each mbigen device node as a interrupt controller.

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Date:	Wed, 14 Oct 2015 16:16:15 +0800
From:	"majun (F)" <majun258@...wei.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Marc Zyngier <marc.zyngier@....com>, <Catalin.Marinas@....com>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <Will.Deacon@....com>,
	<mark.rutland@....com>, <jason@...edaemon.net>,
	<lizefan@...wei.com>, <huxinwei@...wei.com>,
	<dingtianhong@...wei.com>, <zhaojunhua@...ilicon.com>,
	<liguozhu@...ilicon.com>, <xuwei5@...ilicon.com>,
	<wei.chenwei@...ilicon.com>, <guohanjun@...wei.com>,
	<wuyun.wu@...wei.com>, <guodong.xu@...aro.org>,
	<haojian.zhuang@...aro.org>, <zhangfei.gao@...aro.org>,
	<usman.ahmad@...aro.org>, <klimov.linux@...il.com>
Subject: Re: [PATCH v5 1/3] initialize each mbigen device node as a interrupt
 controller.

Hi Thomas:

在 2015/10/13 14:55, Thomas Gleixner 写道:
> Majun,
> 
> On Tue, 13 Oct 2015, majun (F) wrote:
>> 在 2015/10/12 0:45, Thomas Gleixner 写道:
>>> So now in the mbigen case this looks like this:
>>>
>>>     [MSI-BUS] ----- [MBIGEN]<-------------------[Device interrupt]
>>>
>>> Again, you have a 'wire' from the device to the MSI unit (MBIGEN) and
>>> we do not care about that 'wire' either. What we care about is how we
>>> find the MSI (mbigen) configuration registers for a particular
>>> device. So we need a DT/ACPI entry which describes those configuration
>>> registers and whatever supplementary information is required. That
>>> will make the mbigen driver extremly simple.
>>>
>>
>> According to your suggestions, I tried to make the hardware structure likes below:
>>
>> device(8250 uart) -> mbigne -> ITS-pMSI --> ITS --> GIC
> 
> I'm not sure whether mbigen should be connected to ITS-pMSI (I assume
> you mean ITS-PCI-MSI).

ITS domain has two child domains. One is ITS-pMSI for Non-PCI devices,
the other one is ITS-MSI for PCI devices.

> 
> mbigen is a seperate MSI domain, so it should connect to ITS, but I
> leave that to Marc.

I also think mbigen should connected to ITS.

Now, the hierarchy structure is
MBIGEN -> ITS -> GIC.

This structure is really similar to the structure in my v3 patch except the
dts.

>  
>> And  8250 uart dts node is:
>>
>>  8250_uart {
>> 	compatible = "xxx";
>> 	msi-parent = < &mbigen>;
>> 	config_addr = <xxxxx> ; /* configuration register */
>> 	interrupts = <x>;
>> 	interrupt-parent = ?
>> }
>>
>> My question is what's the interrupt-parent should be?
> 
> There is no interrupt parent for 8250_uart. Why would you want that?
> I'm really not a DT expert, but I think you want something like this:
> 
>   8250_uart {
>  	compatible = "xxx";
>  	msi-parent = < &mbigen_node5>;
>  	interrupt-map = <&mbigen5 0>;
>   };
> 

Maybe you mean
interrupt-map = <&mbigen_node5 0>;

I have some questions about this

[1]: I noticed there is no interrupts property,
So, do you mean we don't need this property here ?

[2]: I am confused about interrupt-map.

This property is parsed in function of_irq_parse_raw().
In this fucntion

"
ipar = of_node_get(out_irq->np);
of_get_property(ipar, "interrupt-map", &imaplen);
"
When this function is called by of_irq_parse_one(),
the input para out_irq->np pointed to GIC or mbigen (depends on dts).

So, of_get_property() tried to get the interrupt-map from
GIC or mbgien node.

But there is no interrupt-map property in GIC or mbigen node.



> and then have
> 
>   mbigen_node5 {
>   	...
> 	reg = <....>;
>   };
> 
> So the other devices which are connected to mbigen_node5 have the same
> msi-parent. But then again, please discuss that with Marc and the DT
> wizards.
> 

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