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

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Message-ID: <20200325123742.GA9911@alpha.franken.de>
Date:   Wed, 25 Mar 2020 13:37:42 +0100
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Jiaxun Yang <jiaxun.yang@...goat.com>
Cc:     linux-mips@...r.kernel.org, Huacai Chen <chenhc@...ote.com>,
        Marc Zyngier <maz@...nel.org>,
        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

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 ?

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]