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

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Message-ID: <4BB367D3-B8AD-47B6-ACC2-30752137BC1B@flygoat.com>
Date:   Wed, 25 Mar 2020 21:59:59 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        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9:57:49, Marc Zyngier <maz@...nel.org> 写到:
>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@...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?
>
>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.

Thanks.

So I have to allocate irq_desc here in driver manually?


>
>         M.

-- 
Jiaxun Yang