linux-kernel - Re: [PATCH v2 2/9] drivers: irqchip: Add STM32 external interrupts support

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Date:	Fri, 29 Apr 2016 10:45:14 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <marc.zyngier@....com>,
	Mark Rutland <mark.rutland@....com>,
	Rob Herring <robh+dt@...nel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Daniel Thompson <daniel.thompson@...aro.org>,
	Bruno Herrera <bruherrera@...il.com>,
	Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH v2 2/9] drivers: irqchip: Add STM32 external interrupts support

On Tue, Apr 19, 2016 at 10:00 AM, Maxime Coquelin
<mcoquelin.stm32@...il.com> wrote:
> 2016-04-08 11:38 GMT+02:00 Linus Walleij <linus.walleij@...aro.org>:

>>         while ((stat = readl_relaxed(vic->base + VIC_IRQ_STATUS))) {
>>                 irq = ffs(stat) - 1;
>>                 handle_domain_irq(vic->domain, irq, regs);
>>                 handled = 1;
>>         }
>>
>>         return handled;
>> }
>
> Indeed, it would be better doing it like this.
> Do you think I could even do this with two nested loops to reduce the
> number of reg accesses?
> It would look like this (just compiled, not tested):
>
> static void stm32_irq_handler(struct irq_desc *desc)
> {
>     struct irq_domain *domain = irq_desc_get_handler_data(desc);
>     struct irq_chip_generic *gc = domain->gc->gc[0];
>     struct irq_chip *chip = irq_desc_get_chip(desc);
>     unsigned long pending;
>     int n;
>
>     chained_irq_enter(chip, desc);
>
>     while ((pending = irq_reg_readl(gc, EXTI_PR))) {
>         for_each_set_bit(n, &pending, BITS_PER_LONG) {
>             generic_handle_irq(irq_find_mapping(domain, n));
>         }
>     }

Looks clever! :)

If it also works, I'm in for it.

Yours,
Linus Walleij