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

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Date:	Tue, 4 May 2010 10:23:02 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Bastien Nocera <hadess@...ess.net>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Vojtech Pavlik <vojtech@...e.cz>,
	Robert Hancock <hancockrwd@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>, pjones@...hat.com
Subject: Re: [PATCH] Disable i8042 checks on Intel Apple Macs

On Tue, May 04, 2010 at 06:06:41PM +0100, Bastien Nocera wrote:
> On Mon, 2010-01-25 at 14:15 -0800, 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?
> 
> Doesn't seem to make any difference. It still hangs after saying:
> PNP: No PS/2 controller found. Probing ports directly.
> 
> The patch looks like:
>          udelay(50);
> +        if (str == 0xff)
> +             continue;
>          data = i8042_read_data();
> 
> Not sure that's what you meant above.
> 
> Pressing the power button doesn't make it carry on for me, as it used
> to. Let me know if there's anything more you want me to try.
> 

> In the meantime, I'll try to get my original patch into my distribution
> so I don't get bitten by half-booted kernels in the near future.
> 

Mind resending the original patch? Apparently current situation causes
issues and I guess DMI is not the wost way of taking care of it.

-- 
Dmitry
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