Message-ID: <4B5E18C0.7060402@zytor.com>
Date: Mon, 25 Jan 2010 14:18:40 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
CC: Vojtech Pavlik <vojtech@suse.cz>, Robert Hancock <hancockrwd@gmail.com>,
       Bastien Nocera <hadess@hadess.net>,
       linux-kernel <linux-kernel@vger.kernel.org>, pjones@redhat.com
Subject: Re: [PATCH] Disable i8042 checks on Intel Apple Macs
References: <1264011793.1735.3683.camel@localhost.localdomain> <4B57A2D4.9030204@gmail.com> <20100121185544.GB11996@core.coreip.homeip.net> <51f3faa71001211339t4652700ct34659c37479cd67e@mail.gmail.com> <20100121221701.GA15293@core.coreip.homeip.net> <20100125163433.GB31957@suse.cz> <4B5E0DFA.8080705@zytor.com> <20100125221520.GA30307@core.coreip.homeip.net>
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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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