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 16:35:10 +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 2015/7/8 23:16, Marc Zyngier 写道:
> On 08/07/15 05:21, majun (F) wrote:
>> Hi Thomas:
>>
[...]
>>>> +
>>>> +	nid = GET_NODE_NUM(d->hwirq);
>>>> +	ret = get_mbigen_node_type(nid);
>>>> +	if (ret)
>>>> +		return 0;
>>>
>>> Care to explain what this does? It seems for some nodes you cannot
>>> write the msi message. So how is that supposed to work? How is that
>>> interrupt controlled (mask/unmask ...) ?
>>>
>> This function is used to write irq event id into vector register.Depends on
>> hardware design, write operation is permitted in some mbigen node(nid=0,5,and >7),
>> For other mbigen node, this register is read only.
> 
> So how do you expect this to work? You cannot program the event
> generated by the mbigen, and the ITS has an ITT that probably doesn't
> match your HW.
> 
> Best case, the interrupt is simply dropped, worse case you end up in an
> interrupt storm because you can't figure out which device is screaming.
> 
> 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




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