于 2020年3月25日 GMT+08:00 下午11:46:00, Thomas Bogendoerfer [off-list ref] 写到:

On Wed, Mar 25, 2020 at 11:09:10PM +0800, Jiaxun Yang wrote:

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于 2020年3月25日 GMT+08:00 下午11:04:37, Thomas Bogendoerfer

[off-list ref] 写到:

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On Wed, Mar 25, 2020 at 10:31:21PM +0800, Jiaxun Yang wrote:

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于 2020年3月25日 GMT+08:00 下午10:15:16, Marc Zyngier [off-list ref]

写到:

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On 2020-03-25 13:59, Jiaxun Yang wrote:

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So probably we can use legacy domain when  MIPS IRQ BASE is

in

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the

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range of legacy IRQ
and switch to simple domain when it's not in that range?

No, see below.

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Here in Loongson systems IRQ 0-15 is occupied by I8259 so I

did

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this

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hack.

Well, if you have to consider which Linux IRQ gets assigned,
then your platform is definitely not ready for non-legacy
irqdomains. Just stick to legacy for now until you have

removed

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all the code that knows the hwirq mapping.

Thanks.

So I have to allocate irq_desc here in driver manually?

No, you are probably better off just dropping this patch, as MIPS
doesn't seem to be ready for a wholesale switch to virtual

interrupts.

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It can't work without this patch.

Legacy domain require IRQ number within 0-15 
however it's already occupied by i8259 or "HTPIC" driver.

what's the problem here ? AFAIK there could be more than one
legacy domain, at least that's what at least IP22/SNI in MIPS world 
are doing.

MIPS_IRQ_BASE must be higher than 15, otherwise it will conflict with

i8259.

I still don't get it.

We have following in arch/mips/include/asm/mach-generic/irq.h:

#ifndef MIPS_CPU_IRQ_BASE
#ifdef CONFIG_I8259
#define MIPS_CPU_IRQ_BASE 16
#else
#define MIPS_CPU_IRQ_BASE 0
#endif /* CONFIG_I8259 */
#endif

So every legacy platform with i8259 has MIPS_CPU_IRQ_BASE = 16.

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However we have only preallocated irq_desc for 0-15.
And legacy domain require irq_desc being preallocated.

maybe I'm too fast by judging the irq code, but without
CONFIG_SPARSE_IRQ
the whole irq_desc is pre-allocated.

Sorry. You're right.
I found the problem is CONFIG_SPARSE_IRQ is accidentally enabled in my config due to another out-of-tree patch
during my initial test and I always consider it as a problem.

So we can drop this patch safely for now.
But just need to consider how to deal with it when we want to enable SPARSE_IRQ.

Thanks.

Thomas.

-- 
Jiaxun Yang