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

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Message-ID: <4B5E18C0.7060402@zytor.com>
Date:	Mon, 25 Jan 2010 14:18:40 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.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 01/25/2010 02:15 PM, Dmitry Torokhov wrote:
> 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?
> 

We should never read from port 0x60 unless bit 1 in port 0x64 is set.
Do we do that?

	-hpa

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