linux-kernel - Re: [PATCH 03/11] irqchip: bcm7120-l2: Eliminate bad IRQ check

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Date:	Wed, 29 Oct 2014 09:53:24 -0700
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Kevin Cernekee <cernekee@...il.com>, tglx@...utronix.de,
	jason@...edaemon.net, ralf@...ux-mips.org
CC:	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	mbizon@...ebox.fr, jogo@...nwrt.org, linux-mips@...ux-mips.org
Subject: Re: [PATCH 03/11] irqchip: bcm7120-l2: Eliminate bad IRQ check

On 10/28/2014 08:58 PM, Kevin Cernekee wrote:
> This check may be prone to race conditions, e.g.
> 
> 1) Some external event (e.g. GPIO level) causes an IRQ to become pending
> 2) Peripheral asserts the L2 IRQ
> 3) CPU takes an interrupt
> 4) The event from #1 goes away
> 5) bcm7120_l2_intc_irq_handle() reads back a 0 status
> 
> Unlike the hardware supported by brcmstb-l2, the bcm7120-l2 controller
> does not latch the IRQ status.  Bits can change if the inputs to the
> controller change.  Also, do_bad_IRQ() is an ARM-specific macro.
> 
> So let's just nuke it.
> 
> Signed-off-by: Kevin Cernekee <cernekee@...il.com>

Acked-by: Florian Fainelli <f.fainelli@...il.com>

> ---
>  drivers/irqchip/irq-bcm7120-l2.c | 9 ---------
>  1 file changed, 9 deletions(-)
> 
> 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
> @@ -27,8 +27,6 @@
>  
>  #include "irqchip.h"
>  
> -#include <asm/mach/irq.h>
> -
>  /* Register offset in the L2 interrupt controller */
>  #define IRQEN		0x00
>  #define IRQSTAT		0x04
> @@ -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 {
>  		irq = ffs(status) - 1;
>  		status &= ~(1 << irq);
>  		generic_handle_irq(irq_find_mapping(b->domain, irq));
>  	} while (status);
>  
> -out:
>  	chained_irq_exit(chip, desc);
>  }
>  
> 

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