linux-kernel - Re: [PATCH] Disable i8042 checks on Intel Apple Macs

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Date:	Mon, 25 Jan 2010 14:15:20 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Vojtech Pavlik <vojtech@...e.cz>,
	Robert Hancock <hancockrwd@...il.com>,
	Bastien Nocera <hadess@...ess.net>,
	linux-kernel <linux-kernel@...r.kernel.org>, pjones@...hat.com
Subject: Re: [PATCH] Disable i8042 checks on Intel Apple Macs

On Mon, Jan 25, 2010 at 01:32:42PM -0800, H. Peter Anvin wrote:
> On 01/25/2010 08:34 AM, Vojtech Pavlik wrote:
> > 
> > Thus I believe that the right fix here is to figure out why the accesses
> > to the ports 0x60/0x64 take a long time or forever on a Mac. Is it just
> > that the kernel is timing out waiting for the i8042? Or is it something
> > more sinister?
> > 
> 
> In the A20 code in the setup code, I look for 0xFF coming back and
> terminate the "wait for ready" loop much sooner than for other values.
> 0xFF is a *possible* status value, but not a very *likely* one
> (especially for repeated reads), as it would represent:
> 
> parity error + receive timeout + transmit timeout + keyboard lock +
> command + selftest OK + input full + output full.
> 

You allow up to 32 0xFFs while i8042 driver does maximum 16 reads of
whatever - if OBF is still raised we assume i8042 is not there. Does
that mean that reads from 0x60 is what hurts on Macs?

Bastien, could you try modifying drivers/input/serio/i8042.c::
i8042_flush() to not call i8042_read_data() when str is 0xff and see if
it helps with lockups?

Thanks.

-- 
Dmitry
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