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

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Message-ID: <4B5E0DFA.8080705@zytor.com>
Date:	Mon, 25 Jan 2010 13:32:42 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Vojtech Pavlik <vojtech@...e.cz>
CC:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	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 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.

	-hpa
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