linux-kernel - Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override.

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Message-ID: <4766E2B5.8080001@zytor.com>
Date:	Mon, 17 Dec 2007 12:57:25 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Rene Herman <rene.herman@...il.com>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>, Ingo Molnar <mingo@...e.hu>,
	"David P. Reed" <dpreed@...d.com>, Paul Rolland <rol@...917.net>,
	Pavel Machek <pavel@....cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	rol@...be.net
Subject: Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override.

Rene Herman wrote:
> On 17-12-07 17:12, Alan Cox wrote:
> 
>> I don't think we should be offering udelay based delays at this point.
>> There are a lot of drivers to fix first. This is just one trivial example
> 
> I agree. This thread's too full of people calling this outb method a 
> dumb hack. It's a well-known legacy PC thing and while in practice the 
> udelay might be a functional replacement for a majority of cases (save 
> the races you are finding) a delay proportional to the bus speed makes 
> great sense certainly when talking to hardware that itself runs 
> proportinal to the bus speed for example.
> 
> So, really, how about just sticking in this minimal version for now? 
> Only switches the port to 0xed based on DMI and is all that is needed to 
> fix the actual problem. This should be minimal and no-risk enough that 
> it could also go to .24 if people want it to. It'll fix a few HP laptops 
> (I'll try and get/verify the dv6000z DMI strings as well).
> 

I think retaining the command-line option available is a good thing, 
though.  If nothing else, it is something very quick we can ask other 
people to try if they seem to have similar problems.

Other than that, this alternate-port patch is a low-impact patch not 
affecting hardware not on the blacklist, which makes it appropriate for 
2.6.24 IMO.

	-hpa
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