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

[dayu]

From: Da Yu <dayu@xxxxxxxxxxxxxxx>
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 <dayu@xxxxxxxxxxxxxxx>
---

--- 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
@@ -592,8 +591,7 @@ static void ipic_mask_irq_and_ack(unsign
 	temp &= ~(1 << (31 - ipic_info[src].bit));
 	ipic_write(ipic->regs, ipic_info[src].mask, temp);

-	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




-----邮件原件-----
发件人: Li Yang [mailto:leoli@xxxxxxxxxxxxx] 
发送时间: 2009年2月17日 22:38
收件人: Kumar Gala
抄送: 笪禹; linux-kernel@xxxxxxxxxxxxxxx; linuxppc-dev@xxxxxxxxxx
主题: Re: [PATCH] fix the interrupt loss problem on powerpc IPIC (2.6.23)

On Tue, Feb 17, 2009 at 10:12 PM, Kumar Gala <galak@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Feb 17, 2009, at 6:44 AM, <dayu@xxxxxxxxxxxxxxx> 
> <dayu@xxxxxxxxxxxxxxx>
> wrote:
>
>> From: Da Yu <dayu@xxxxxxxxxxxxxxx>
>> Date: Tue, 17 Feb 2009 19:58:20 +0800
>> Subject: [PATCH] fix the interrupt loss problem on powerpc IPIC 
>> (2.6.23)
>>
>> Signed-off-by: Da Yu <dayu@xxxxxxxxxxxxxxx>
>> ---
>
> Please provide a bit more description as to why this fixes the issue.

The pending register is write 1 clear.  If there are more than one external interrupts pending at the same time, acking the first interrupt will also clear other interrupt pending bits.  That will cause loss of interrupt.

- Leo
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