linux-kernel - Re: [BUG 2.6.20-rc2] atkbd.c: Spurious ACK

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Date:	Sat, 30 Dec 2006 12:19:58 +0100
From:	Laurent Riffard <laurent.riffard@...e.fr>
To:	Rene Herman <rene.herman@...il.com>
Cc:	Dmitry Torokhov <dtor@...ightbb.com>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Vojtech Pavlik <vojtech@...e.cz>
Subject: Re: [BUG 2.6.20-rc2] atkbd.c: Spurious ACK

Le 30.12.2006 08:20, Rene Herman a écrit :
> Dmitry Torokhov wrote:
> 
>> Somehow you get 2 ACks in a row, I wonder if on your boxes i8042
>> pumps command and data into keyboard before i8042_interrupt gets a
>> chance to run. Could you please apply the debug patch below and tell
>> me the pattern of the data flow.
> 
> Yes, I believe the below trace confirms what you said? Both the ED and 
> the 00/05 are sent before the first ACK gets back, by a 1 jiffie margin:
> 
> drivers/input/serio/i8042.c: ed -> i8042 (panic blink) [N]
> drivers/input/serio/i8042.c: 05 -> i8042 (panic blink) [N + 2]
> drivers/input/serio/i8042.c: fa <- i8042 (interrupt, 0, 1) [N + 3]
> drivers/input/serio/i8042.c: fa <- i8042 (interrupt, 0, 1) [N + 6]
> drivers/input/serio/i8042.c: ed -> i8042 (panic blink) [M]
> drivers/input/serio/i8042.c: 00 -> i8042 (panic blink) [M + 2]
> drivers/input/serio/i8042.c: fa <- i8042 (interrupt, 0, 1) [M + 3]
> drivers/input/serio/i8042.c: fa <- i8042 (interrupt, 0, 1) [M + 6]
> 
> The +2, +3 and +6 are constant. Forgot to pay attention to M - N, but I 
> suppose it's not too important.
> 
> For me, the patch as you posted it is actually good to go. No more 
> spurious ACK complaints...
> 
> Thanks,
> Rene.

Hi Dmitry, Rene

I can confirm Rene's report: this patch works fine since there is no more "Spurious 
ACK on isa0060/serio0" message.

Here is a debug output as requested:

 <0>Kernel panic - not syncing: Fatal exception in interrupt
 <7>drivers/input/serio/i8042.c: 13 <- i8042 (interrupt, 0, 1) [49602]
drivers/input/serio/i8042.c: 93 <- i8042 (interrupt, 0, 1) [49603]
drivers/input/serio/i8042.c: ed -> i8042 (panic blink) [49728]
drivers/input/serio/i8042.c: 05 -> i8042 (panic blink) [49729]
drivers/input/serio/i8042.c: fa <- i8042 (interrupt, 0, 1) [49730]
drivers/input/serio/i8042.c: fa <- i8042 (interrupt, 0, 1) [49732]
drivers/input/serio/i8042.c: ed -> i8042 (panic blink) [49856]
drivers/input/serio/i8042.c: 00 -> i8042 (panic blink) [49857]
drivers/input/serio/i8042.c: fa <- i8042 (interrupt, 0, 1) [49858]
drivers/input/serio/i8042.c: fa <- i8042 (interrupt, 0, 1) [49860]
drivers/input/serio/i8042.c: ed -> i8042 (panic blink) [49983]
drivers/input/serio/i8042.c: 05 -> i8042 (panic blink) [49985]
drivers/input/serio/i8042.c: fa <- i8042 (interrupt, 0, 1) [49986]
drivers/input/serio/i8042.c: fa <- i8042 (interrupt, 0, 1) [49988]
drivers/input/serio/i8042.c: ed -> i8042 (panic blink) [50112]
drivers/input/serio/i8042.c: 00 -> i8042 (panic blink) [50114]
drivers/input/serio/i8042.c: fa <- i8042 (interrupt, 0, 1) [50115]
drivers/input/serio/i8042.c: fa <- i8042 (interrupt, 0, 1) [50117]

thanks
-- 
laurent
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