linux-kernel - Re: [PATCH] acpi: Avoid dropping rapid hotkey events (or other GPEs) on Asus EeePC

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Date:	Wed, 13 Aug 2008 11:21:10 +0100
From:	Alan Jenkins <alan-jenkins@...fmail.co.uk>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Alexey Starikovskiy <astarikovskiy@...e.de>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	hmh@....eng.br, Maximilian Engelhardt <maxi@...monizer.de>,
	linux-stable@...r.kernel.org
Subject: Re: [PATCH] acpi: Avoid dropping rapid hotkey events (or other GPEs)
 on Asus EeePC

Andrew Morton wrote:
> Did this get fixed yet?
>
> I have an patch in -mm which I just restored (I had to tempdrop it
> because the acpi tree was busted for some time).  But it seems to be
> old.
>
> http://bugzilla.kernel.org/show_bug.cgi?id=10919 is marked "resolved"
> but the reporter (Maximilian) seems to think otherwise.  2.6.26.x is,
> afaik, still unfixed, as is 2.6.27-rc.
>   
That's correct.  I think this specific patch should go in 2.6.27 and
2.6.26-stable.  No objections have been raised so far.

I still need this patch to make my brightness and volume control keys
usable in 2.6.27-rc3.  (They auto-repeat fast enough to trigger the
bug).  This is true even after applying the latest patches from bug
10919 (#25 + #27).

I think the 10919 fix makes it harder to reproduce, but it definitely
still happens.  I guess this is because the polling-driven EC
transactions add 1ms delays between each byte.  The slower timings leave
a window where the buggy behaviour of my EC can make a difference.  (It
has been seen to clear the "pending event" bit after a single event is
read, despite having more events pending).

There are more serious consequences of this bug.  After a while it can
confuse the EC enough to cause lockups or reboots during boot, or after
pressing a single hotkey.  This bad state is preserved over reboots,
even into known good kernels.  Fortunately the badness clears when power
is removed for a long enough period.  For a while I was worried that
something had physically burnt out.

Thanks
Alan
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