linux-kernel - Re: [PATCH] x86: use explicit timing delay for pit accesses in kernel and pcspkr driver

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Message-ID: <47BA0188.6000808@keyaccess.nl>
Date:	Mon, 18 Feb 2008 23:07:04 +0100
From:	Rene Herman <rene.herman@...access.nl>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	"David P. Reed" <dpreed@...d.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Dmitry Torokhov <dtor_core@...ritech.net>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: use explicit timing delay for pit accesses in kernel
 and pcspkr driver

On 18-02-08 23:01, H. Peter Anvin wrote:

> Rene Herman wrote:
>>
>> Yes, but generally not any P5+ system is going to need the PIT delay 
>> in the first place meaning it just doesn't matter. There were the VIA 
>> issues with the PIC but unless I missed it not with the PIT.
>>
> 
> Uhm, I'm not sure I believe that's safe.
> 
> The PIT is particularly pissy in this case -- the semantics of the PIT 
> are ill-defined if there hasn't been a PIT clock between two adjacent 
> accesses, so I fully expect that there are chipsets out there which will 
> do very bad things in this case.

Okay. Now that they're isolated, do you have a suggestion for {in,out}b_pit? 
You say a PIT clock, so do you think we can bounce of the PIT iself in this 
case after all?

Rene.
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