RE: [PATCH] Add quirk to set AHCI mode on ICH boards

Allen Martin
2007-11-10T18:42:32Z

> Alan Cox wrote:
> > On Thu, 8 Nov 2007 22:46:22 -0500
> > Jeff Garzik <jeff@garzik.org> 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... :/
> >
> > We've done it all the time for various devices without
> problems (eg S3
> > video cards). I'd like to see it go in - although perhaps
> attached to
> > a force_ahci boot param initially
>
> By forcing AHCI, your PATA devices will be inaccessible, in a
> common configuration. It also means shuffling users from one
> driver to another, which induces breakage.
>
> I was speaking wishfully. Real life intrudes, alas.
>

At least for NVIDIA controllers, loading the AHCI driver when the BIOS
is set to IDE mode is not recommended by NVIDIA. Any AHCI workarounds
in the BIOS are likely to be disabled when set to IDE mode. In practice
we don't expect to see a lot of users running an AHCI controller in IDE
mode unless they have explicitly disabled AHCI from the BIOS or the
system builder has some specific reason for shipping IDE mode by default
(like support for some legacy DOS or Win9x tools)

-Allen
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