linux-kernel - Re: [PATCH] Add quirk to set AHCI mode on ICH boards

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Message-ID: <20071109070230.73eb7be5@laptopd505.fenrus.org>
Date:	Fri, 9 Nov 2007 07:02:30 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Jeff Garzik <jeff@...zik.org>
Cc:	Mark Lord <liml@....ca>, Riki Oktarianto <rkoktarianto@...il.com>,
	linux-kernel@...r.kernel.org, Greg Kroah-Hartman <gregkh@...e.de>,
	linux-ide@...r.kernel.org
Subject: Re: [PATCH] Add quirk to set AHCI mode on ICH boards

On Thu, 8 Nov 2007 23:57:48 -0500
Jeff Garzik <jeff@...zik.org> wrote:

> On Thu, Nov 08, 2007 at 11:44:22PM -0500, Mark Lord wrote:
> > Jeff Garzik wrote:
> > >On Thu, Nov 08, 2007 at 10:29:37PM -0500, Mark Lord wrote:
> > >>And I might even privately patch my own kernels to map the ACHI
> > >>BAR in the cases where the BIOS didn't...
> > >
> > >The inability to do this in the general case is the main reason why
> > >AHCI was not unconditionally enabled, even in IDE mode, when it was
> > >originally added...  :/
> > ..
> > 
> > Yeah, that one's always puzzled me.
> > It's just software,  so why don't we do it?  In the PCI layer, that
> > is?
> 
> Ah, but it's not just software:  when trying to find bus address
> space for the BAR, we don't know if we are stomping on magic hardware
> resources the BIOS has conveniently failed to tell us about.
> 
> So while in all likelihood you will have no problem finding a
> suitable bus address to use, as a generalized rule it is a far more
> difficult proposition.
> 

another thing to test before doing this everywhere is suspend/resume.
This would use the hardware in a way the bios doesn't expect, and sadly
that kind of thing tends to royally b0rk the suspend/resume code often
(but of course not always).


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