Re: Enabling AHCI on ICH7 without BIOS support

["Török Edwin" <edwintorok@gmail.com>]

Tejun Heo <htejun <at> gmail.com> writes:

> ISHIKAWA Mutsumi wrote:
> >  Do you know Edvin's patch?
> > 
> > http://www.bughost.org/pipermail/power/2007-June/000538.html
> > 
> >  I've tested it and works fine on my note
> > (Sony VAIO type S VGN-SZ92PS, ICH7-M)

Thanks for testing.

> 
> Yeah, I've seen it but I'm not sure whether it would worth the risk.
> For one, there are BIOSen which won't assign IO memory region to ABAR at
> all.  There also is a patch to reallocate IO memory regions and make
> room for ABAR but that can break things.
> 

It works fine on 2.6.22 (except that you loose the CD-ROM, and I found no way to
reliably reactivate it), however since 2.6.23-rc it breaks.
I get misrouted IRQs: IRQ 12 (keyboard) is being fired instead of IRQ 18 (ahci),
the kernel disables IRQ 18 because of spurious IRQs, and then IRQ 0 gets fired
instead of IRQ 18. It is an edge-triggered interrupt, and I get the feeling  the
interrupt status isn't cleared after handling it, since I continously get
messages about misrouted IRQs even if the system idle.
It works with irqpoll, but I don't have to tell you how slow that is.

When I'll be back from holiday I will try to compare lspci -xxx outputs, and
then maybe try a git-bisect.

Bottom line is that force-enabling AHCI like this can stop working at any time
with a new kernel version.
If there is a document describing _exactly_ what steps I need to follow to
properly enable the device, I'd be happy to read it, but I guess such
documentation is only available to BIOS developers.

--Edwin