Subject: Re: [PATCH] fix the interrupt loss problem on powerpc IPIC (2.6.25-2.6.28)

From: Olof Johansson <[email-masked]>
Date: Tue, 17 Feb 2009 20:43:12 -0600

On Wed, Feb 18, 2009 at 10:16:07AM +0800, [email-masked] wrote:
> From: Da Yu <[email-masked]>
> Date: Wed, 18 Feb 2009 19:58:20 +0800
> Subject: [PATCH] fix the interrupt loss problem on powerpc IPIC (2.6.25-2.6.28)
> 
> Signed-off-by: Da Yu <[email-masked]>

Still no proper explanation in the patch.

Also, with this change, is 'temp' really needed, or can you just pass in the
mask by hand?

-Olof

> ---
> 
> --- a/arch/powerpc/sysdev/ipic.c	2009-02-18 09:47:04.000000000 +0800
> +++ b/arch/powerpc/sysdev/ipic.c	2009-02-18 09:46:34.000000000 +0800
> @@ -568,8 +568,7 @@ static void ipic_ack_irq(unsigned int vi
> 
>  	spin_lock_irqsave(&ipic_lock, flags);
> 
> -	temp = ipic_read(ipic->regs, ipic_info[src].ack);
> -	temp |= (1 << (31 - ipic_info[src].bit));
> +	temp = 1 << (31 - ipic_info[src].bit);
>  	ipic_write(ipic->regs, ipic_info[src].ack, temp);
> 
>  	/* mb() can't guarantee that ack is finished.  But it does finish