linux-kernel - Re: [PATCH v8 06/11] irqchip: mips-cpu: Convert to simple domain

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Message-ID: <C4892878-8463-448D-897B-5F2C56F5A340@flygoat.com>
Date:   Wed, 25 Mar 2020 21:07:04 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     Marc Zyngier <maz@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>
CC:     linux-mips@...r.kernel.org, Huacai Chen <chenhc@...ote.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Allison Randal <allison@...utok.net>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v8 06/11] irqchip: mips-cpu: Convert to simple domain



于 2020年3月25日 GMT+08:00 下午9:00:01, Marc Zyngier <maz@...nel.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@...goat.com>
>>> Co-developed-by: Huacai Chen <chenhc@...ote.com>
>>> Signed-off-by: Huacai Chen <chenhc@...ote.com>
>>> Reviewed-by: Marc Zyngier <maz@...nel.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?

Here in Loongson systems IRQ 0-15 is occupied by I8259 so I did this hack.

Thanks.

>
>Thanks,
>
>         M.
 
-- 
Jiaxun Yang