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SubjectRe: [PATCH v8 06/11] irqchip: mips-cpu: Convert to simple domain
On 2020-03-25 13:07, Jiaxun Yang wrote:
> 于 2020年3月25日 GMT+08:00 下午9:00:01, Marc Zyngier <maz@kernel.org> 写到:
>> On 2020-03-25 12:37, Thomas Bogendoerfer wrote:
>>> On Wed, Mar 25, 2020 at 11:54:59AM +0800, Jiaxun Yang wrote:
>>>> The old code is using legacy domain to setup irq_domain for CPU
>>>> interrupts
>>>> which requires irq_desc to be preallocated.
>>>>
>>>> However, when MIPS_CPU_IRQ_BASE >= 16, irq_desc for CPU IRQs may end
>>
>>>> up
>>>> unallocated and lead to incorrect behavior.
>>>>
>>>> Thus we convert the legacy domain to simple domain which can
>> allocate
>>>> irq_desc during initialization.
>>>>
>>>> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
>>>> Co-developed-by: Huacai Chen <chenhc@lemote.com>
>>>> Signed-off-by: Huacai Chen <chenhc@lemote.com>
>>>> Reviewed-by: Marc Zyngier <maz@kernel.org>
>>>> ---
>>>> drivers/irqchip/irq-mips-cpu.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/irqchip/irq-mips-cpu.c
>>>> b/drivers/irqchip/irq-mips-cpu.c
>>>> index 95d4fd8f7a96..c3cf7fa76424 100644
>>>> --- a/drivers/irqchip/irq-mips-cpu.c
>>>> +++ b/drivers/irqchip/irq-mips-cpu.c
>>>> @@ -251,7 +251,7 @@ static void __init __mips_cpu_irq_init(struct
>>>> device_node *of_node)
>>>> clear_c0_status(ST0_IM);
>>>> clear_c0_cause(CAUSEF_IP);
>>>>
>>>> - irq_domain = irq_domain_add_legacy(of_node, 8, MIPS_CPU_IRQ_BASE,
>> 0,
>>>> + irq_domain = irq_domain_add_simple(of_node, 8, MIPS_CPU_IRQ_BASE,
>>>> &mips_cpu_intc_irq_domain_ops,
>>>> NULL);
>>>
>>> this breaks at least IP30 and guess it will break every platform
>> where
>>> MIPS_CPU_IRQ_BASE == 0. add_legacy will always do
>>> irq_domain_associate_many(),
>>> while add_simple doesn't do it, if first_irq == 0.
>>>
>>> Marc, what is the reason not doing it all the time ? What's the
>> correct
>>> way here to work with irq_domain_add_simple() in this case ?
>>
>> On a fully DT-ified platform, using non-legacy irqdomains, virtual
>> interrupts
>> are allocated as a "random" number, depending on the order of
>> allocation,
>> and on demand.
>>
>> The first_irq hack in irq_domain_add_simple() is just a way to still
>> allocate
>> descriptors upfront (and I wish we could drop it...).
>>
>> If you have legacy code that "knows" about the relationship between
>> Linux's
>> virtual interrupt and the hwirq (that is only meaningful to the
>> interrupt
>> controller), you're screwed, and need to stick to the legacy
>> irqdomain.
>>
>> It feels like the MIPS code is squarely in the latter case, so I guess
>> this
>> patch is probably the wrong thing to do for this architecture.
>
> So probably we can use legacy domain when MIPS IRQ BASE is in the
> range of legacy IRQ
> and switch to simple domain when it's not in that range?

No, see below.

> Here in Loongson systems IRQ 0-15 is occupied by I8259 so I did this
> 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
all the code that knows the hwirq mapping.

M.
--
Jazz is not dead. It just smells funny...

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