linux-kernel - Re: [PATCH v2 4/5] irqchip:create irq domain for each mbigen device

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Date:	Wed, 17 Feb 2016 12:18:52 +0800
From:	"majun (F)" <majun258@...wei.com>
To:	Marc Zyngier <marc.zyngier@....com>
CC:	<Catalin.Marinas@....com>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <Will.Deacon@....com>,
	<mark.rutland@....com>, <jason@...edaemon.net>,
	<tglx@...utronix.de>, <lizefan@...wei.com>, <huxinwei@...wei.com>,
	<dingtianhong@...wei.com>, <liguozhu@...ilicon.com>,
	<guohanjun@...wei.com>, <zhaojunhua@...ilicon.com>
Subject: Re: [PATCH v2 4/5] irqchip:create irq domain for each mbigen device



在 2016/2/16 16:50, Marc Zyngier 写道:
> On Tue, 16 Feb 2016 14:37:27 +0800
> MaJun <majun258@...wei.com> wrote:
> 
>> From: Ma Jun <majun258@...wei.com>
[...]
>> +	unsigned int nid;
>> +
>> +	nid = get_mbigen_nid(hwirq);
>> +
>> +	if (nid < 4)
>> +		return (nid * 4) + REG_MBIGEN_VEC_OFFSET;
>> +	else
>> +		return (nid - 4) * 4 + REG_MBIGEN_EXT_VEC_OFFSET;
>> +}
>> +
>> +static struct irq_chip mbigen_irq_chip = {
>> +	.name =			"mbigen-v1",
>> +};
>> +
>> +static void mbigen_write_msg(struct msi_desc *desc, struct msi_msg *msg)
>> +{
>> +	/* The address of doorbell is encoded in mbigen register by default
>> +	 * So,we don't need to program the doorbell address at here
>> +	 * Besides, the event ID is decided by the hardware pin number,
>> +	 * we can't change it in software.So, we don't need to encode the
>> +	 * event ID in mbigen register.
>> +	 */
> 
> Really? What if tomorrow I decide to change the EventID allocation
> policy in the ITS driver? Have your HW engineers really baked the
> behaviour of the Linux driver into the device?
> 

Yes.
If we really need to support this chip,is there
any possible solution for this problem?

Thanks!
MaJun

> I'm puzzled.
> 
> 	M.
>