Re: [patch 2.5] PCI: allow alternative methods for probing the BARs

[Linus Torvalds]

On 7 Jan 2003, Alan Cox wrote:
>
> On Tue, 2003-01-07 at 00:13, Grant Grundler wrote:
> > On Mon, Jan 06, 2003 at 03:19:09PM -0800, Linus Torvalds wrote:
> > > In particular, we can make the first phase disable DMA on the devices we 
> > > find, which means that we know they won't be generating PCI traffic during 
> > > the second phase - so now the second phase (which does the BAR sizing) can 
> > > do sizing and be safe in the knowledge that there should be no random PCI 
> > > activity ongoing at the same time.
> > 
> > Did you expect the PCI_COMMAND_MASTER disabled in the USB Controller
> > or something else in the controller turned off?
> 
> There is another problem too. Some devices ignore the master bit disable.
> VIA 8233/8235 being a fine example.

Well, I was actually thinking of really _stopping_ the USB controller and
disable DMA that way.  That's easy to do with a few trivial fixups - one
for each USB controller type (and there are only three).

Because of legacy USB handling by the SMM BIOS, USB really ends up being a
special case. There may be other special cases, of course, but the whole 
point of the fixups is exactly to handle special cases.

		Linus