linux-kernel - Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops

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Message-ID: <475CBDD7.5050602@keyaccess.nl>
Date:	Mon, 10 Dec 2007 05:17:27 +0100
From:	Rene Herman <rene.herman@...access.nl>
To:	Pavel Machek <pavel@....cz>
CC:	Andi Kleen <andi@...stfloor.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	"David P. Reed" <dpreed@...d.com>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64
 with MCP51 laptops

On 09-12-07 22:25, Pavel Machek wrote:

> On Sun 2007-12-09 17:59:08, Andi Kleen wrote:

>> Yes, i guess switching to udelay at least on newer systems would
>> be a good idea.  I'm not quite sure about systems without TSC though.
> 
> Something like this? (Warning, will not probably even compile on
> x86-64, I do not have 64-bit compiler near me).

>  static inline void native_io_delay(void)
>  {
> -	asm volatile("outb %%al,$0x80" : : : "memory");
> +	udelay(8);
>  }

Alan, did you double-check that 8 us? I tried to but I seem to not have 
trustworthy documentation.

Rene.
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