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

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Message-ID: <47BA09FE.50507@zytor.com>
Date:	Mon, 18 Feb 2008 14:43:10 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Rene Herman <rene.herman@...access.nl>
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

Rene Herman wrote:
>>
>> 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?

No, I don't think so.

	-hpa
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