linux-kernel - Re: [PATCH v3 1/3] IRQ/Gic-V3: Add mbigen driver to support mbigen interrupt controller

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Date:	Thu, 16 Jul 2015 17:22:05 +0800
From:	"majun (F)" <majun258@...wei.com>
To:	Marc Zyngier <marc.zyngier@....com>,
	Thomas Gleixner <tglx@...utronix.de>
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>,
	"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 v3 1/3] IRQ/Gic-V3: Add mbigen driver to support mbigen
 interrupt controller



在 2015/7/16 16:52, Marc Zyngier 写道:
> On 16/07/15 09:35, majun (F) wrote:

>>> I'm a bit puzzled.
>>
>> For interrupts connect to mbigen , the interrupt trigger type, device id and
>> event id value are encoded in mbigen chip already.
>>
>> There are two types of mbigen node within a mbigen chip.
>> Type1: event id valud can't be programmed.
>> Type2: event id value can be programmed.
>>
>> For example: An device with 5 interrupts connected to Mbigen node
>> type 1.The default event id vlaue encoded in mbigen chip for these 5 interrupt
>> is from 0 to 4.
>>
>> Because the event id value can't be programmed, we need to define all of
>> 5 interrupts in dts file so that these 5 interrupt has
> 
> You can define what you want in the device tree, the ITS doesn't care!
> Nothing in the ITS code parses this property, and there is absolutely
> zero chance that the even the ITS has allocated will actually match what
> you expect.
> 
> The ITS *relies* on the principle that the evenID can be programmed,
> just like any MSI controller relies on the device to be programmed with
> whatever payload has been provided. If all of a sudden we have to
> support HW that has its own view of the payload, what you have here will
> simply not work.
> 
"If all of a sudden we have to
 support HW that has its own view of the payload, what you have here will
 simply not work."

I am not very unstand this case, would you please explain this more detail?
Thanks!


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