linux-kernel - Re: [PATCH V2 08/15] irqchip: bcm7120-l2: Eliminate bad IRQ check

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Message-ID: <CAJiQ=7BekWsmcDfQ-oKXAza_pEXHNFCQAisvo2m+D7Km2t_meQ@mail.gmail.com>
Date:	Thu, 30 Oct 2014 12:24:02 -0700
From:	Kevin Cernekee <cernekee@...il.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Florian Fainelli <f.fainelli@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Paul Mundt <lethal@...ux-sh.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Maxime Bizon <mbizon@...ebox.fr>,
	Jonas Gorski <jogo@...nwrt.org>,
	Linux MIPS Mailing List <linux-mips@...ux-mips.org>
Subject: Re: [PATCH V2 08/15] irqchip: bcm7120-l2: Eliminate bad IRQ check

On Thu, Oct 30, 2014 at 4:09 AM, Sergei Shtylyov wrote:
>> diff --git a/drivers/irqchip/irq-bcm7120-l2.c
>> b/drivers/irqchip/irq-bcm7120-l2.c
>> index b9f4fb8..49d8f3d 100644
>> --- a/drivers/irqchip/irq-bcm7120-l2.c
>> +++ b/drivers/irqchip/irq-bcm7120-l2.c
>
> [...]
>>
>> @@ -51,19 +49,12 @@ static void bcm7120_l2_intc_irq_handle(unsigned int
>> irq, struct irq_desc *desc)
>>         chained_irq_enter(chip, desc);
>>
>>         status = __raw_readl(b->base + IRQSTAT);
>> -
>> -       if (status == 0) {
>> -               do_bad_IRQ(irq, desc);
>> -               goto out;
>> -       }
>> -
>>         do {
>
>
>    I think this needs to now become:
>
>         while (status) {
>
>>                 irq = ffs(status) - 1;
>>                 status &= ~(1 << irq);
>
>
>    In case 'status' is 0, 'irq' will be equal to -1. How does the shift by
> negative value work?
>
>>                 generic_handle_irq(irq_find_mapping(b->domain, irq));
>>         } while (status);

That's a good point.  We need to check for 0 somehow.

This code gets replaced in patch 13/15 anyway, but I'll fix it in the
next round.

Thanks!
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