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: <20071215230036.GF2434@elf.ucw.cz>
Date:	Sun, 16 Dec 2007 00:00:36 +0100
From:	Pavel Machek <pavel@....cz>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"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>,
	Rene Herman <rene.herman@...access.nl>
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 14:15:03, Ingo Molnar wrote:
> 
> * David P. Reed <dpreed@...d.com> wrote:
> 
> > Replace use of outb to "unused" diagnostic port 0x80 for time delay 
> > with udelay based time delay on x86_64 architecture machines.  Fix for 
> > bugs 9511 and 6307 in bugzilla, plus bugs reported in 
> > bugzilla.redhat.com.
> >
> > Derived from suggestion (that didn't compile) by Pavel Machek, and 
> > tested, also based on measurements of typical timings of out's 
> > collated by Rene Herman from many in the community.
> >
> > This patch fixes a number of bugs known to cause problems on HP
> > Pavilion dv9000z and dv6000z laptops - in the form of solid freezes
> > when hwclock is used to show or set the time.  Also, it potentially
> > improves bus utilization on SMP machines, by using a waiting process
> > that doesn't tie up the ISA/LPC bus for 1 or 2 microseconds.
> >
> > i386 family fixes (completely parallel) were not included, considering 
> > that such machines might involve more risk of problems on legacy 
> > machines.
> 
> wow, cool fix! (I remember that there were other systems as well that 
> are affected by port 0x80 muckery - i thought we had removed port 0x80 
> accesses long ago.)
> 
> how about the simpler fix below, as a first-level approach? We can then 
> remove the _p in/out sequences after this.
> 
> this is also something for v2.6.24 merging.

As much as I like this patch, I do not think it is suitable for
.24. Too risky, I'd say.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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