linux-kernel - Re: [PATCH 02/35] ARM: davinci: select GENERIC_IRQ_MULTI

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Date:   Mon, 4 Feb 2019 16:02:11 -0600
From:   David Lechner <david@...hnology.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>, Sekhar Nori <nsekhar@...com>,
        Kevin Hilman <khilman@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 02/35] ARM: davinci: select GENERIC_IRQ_MULTI_HANDLER

On 1/31/19 7:38 AM, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> 
> In order to support SPARSE_IRQ we first need to make davinci use the
> generic irq handler for ARM. Translate the legacy assembly to C and
> put the irq handlers into their respective drivers (aintc and cp-intc).
> 
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> ---

...

> diff --git a/arch/arm/mach-davinci/cp_intc.c b/arch/arm/mach-davinci/cp_intc.c

...

> @@ -97,6 +98,16 @@ static struct irq_chip cp_intc_irq_chip = {
>   
>   static struct irq_domain *cp_intc_domain;
>   
> +static asmlinkage void __exception_irq_entry
> +cp_intc_handle_irq(struct pt_regs *regs)
> +{
> +	int irqnr = cp_intc_read(CP_INTC_PRIO_IDX);
> +
> +	irqnr &= 0xff;

What does applying the 0xff mask do? (perhaps needs a code
comment if it is important and not obvious).

> +
> +	handle_domain_irq(cp_intc_domain, irqnr, regs);
> +}
> +
>   static int cp_intc_host_map(struct irq_domain *h, unsigned int virq,
>   			  irq_hw_number_t hw)
>   {

...

> diff --git a/arch/arm/mach-davinci/irq.c b/arch/arm/mach-davinci/irq.c

...

> @@ -69,6 +76,19 @@ davinci_alloc_gc(void __iomem *base, unsigned int irq_start, unsigned int num)
>   			       IRQ_NOREQUEST | IRQ_NOPROBE, 0);
>   }
>   
> +static asmlinkage void __exception_irq_entry
> +davinci_handle_irq(struct pt_regs *regs)
> +{
> +	int irqnr = davinci_irq_readl(IRQ_IRQENTRY_OFFSET);
> +	struct pt_regs *old_regs = set_irq_regs(regs);
> +
> +	irqnr >>= 2;
> +	irqnr -= 1;

Same here. It is not obvious to me what sort of conversion
is going on here.

> +
> +	generic_handle_irq(irqnr);
> +	set_irq_regs(old_regs);
> +}
> +
>   /* ARM Interrupt Controller Initialization */
>   void __init davinci_irq_init(void)
>   {