linux-kernel - Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc.

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Message-ID: <20071214210532.GA28793@elf.ucw.cz>
Date:	Fri, 14 Dec 2007 22:05:32 +0100
From:	Pavel Machek <pavel@....cz>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Rene Herman <rene.herman@...il.com>, Ingo Molnar <mingo@...e.hu>,
	"David P. Reed" <dpreed@...d.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80
	on some AMD64x2 laptops, etc.

On Fri 2007-12-14 18:36:26, Alan Cox wrote:
> > > i dont think this should matter: old systems that truly _need_ the ISA 
> > > delay will be slow enough to not trip up. (nor are they really affected 
> > > by these early delays - the delays were more for crappy ISA devices that 
> > > get initialized later down, when the delay loop is already calibrated)
> > 
> > 8253 (DMAC) and 8254 (PIT) have been reported in earlier versions of the 
> > thread. By Alan, I believe.
> 
> They've been seen to be problems up to PII era machines. I'm not aware of
> any newer than that with this problem. We also don't need to touch the
> DMAC that early anyway that I can see - just the PIT.
> 
> In fact if we have a fast processor we have a TSC and APIC so we don't
> need the PIT ?

It is still good to be able to disable APIC/TSC. Neither are
particulary reliable time sources.

-- 
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