Re: [git patches] libata updates for 3.3

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

On Mon, 16 Jan 2012 11:47:12 -0800
Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Mon, Jan 16, 2012 at 11:42 AM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> >
> > There are two sets of problems with that
> >
> > The first is that quite a few machines crap themselves if you do this
> > because nobody has ever tested things like the IRQ routing or the
> > firmware on suspend/resume when they find the hardwared controller has
> > gone for a walk.
> 
> I think this could trivially be solved at least on these kinds of
> Apple machines by just making it a config option, and just not doing
> it if it doesn't work. Some kernel command line to say "ahci=force" or
> whatever.

There are patches for this from way back including a white list of
devices that were tested

Just ping Matthew about

http://www.codon.org.uk/~mjg59/tmp/ahci_quirk_cleanup.diff

> That doesn't solve the "user never even realized" problem, but at
> least it gives the user the possibility of solving the "crap firmware
> doesn't even allow this".

For the "memory found over 4GB" case it may even be worth printing a
warning.

> > Putting it back on suspend might help in some cases but then you get to
> > pick your way through the documentation minefield, deal with device
> > changes while in non AHCI mode, figure out how to set up registers the
> > BIOS didn't etc.
> 
> Yeah, no, that would just be horrible. I doubt it happens in practice,
> though.  I bet the normal PCI/AHCI resume will just do the right
> thing. But I haven't tried..

Some BIOSes go off and try and re-unlock the drive with the bios password
etc. They get most unhappy when the controller isn't in the mode they
expected. Matthew used a white list for some he tested which didn't have
problems. Most netbooks seem ok with it.

Alan