Re: [PATCH] PCI/Cardbus cards hidden, needs pci=assign-busses to fix

[Greg KH <greg@kroah.com>]

On Sat, Feb 18, 2006 at 01:41:02AM -0800, Andrew Morton wrote:
> Bernhard Kaindl <bk@suse.de> wrote:
> >
> > "In some cases, especially on modern laptops with a lot of PCI and cardbus
> >  bridges, we're unable to assign correct secondary/subordinate bus numbers
> >  to all cardbus bridges due to BIOS limitations unless we are using
> >  "pci=assign-busses" boot option." -- Ivan Kokshaysky (from a patch comment)
> > 
> >  Without it, Cardbus cards inserted are never seen by PCI because the
> >  parent PCI-PCI Bridge of the Cardbus bridge will not pass and translate
> >  Type 1 PCI configuration cycles correctly and the system will fail to
> >  find and initialise the PCI devices in the system.
> > 
> >  Reference: PCI-PCI Bridges: PCI Configuration Cycles and PCI Bus Numbering:
> >  http://www.science.unitn.it/~fiorella/guidelinux/tlk/node72.html
> > 
> >  The reason for this is that:
> >   ``All PCI busses located behind a PCI-PCI bridge must reside between the
> >  secondary bus number and the subordinate bus number (inclusive).''
> > 
> >  "pci=assign-busses" makes pcibios_assign_all_busses return 1 and this
> >  turns on PCI renumbering during PCI probing.
> > 
> >  Alan suggested to use DMI to make that function cause that on problem systems:
> >
> > [ snip patch which uses a DMI table to auto-set "pci=assign-busses" ]
> >
> 
> I guess if this is the only way in which we can do this, and nobody has any
> better solutions then sure, it'll get people's machines going.  We'll be
> forever patching that table though.
> 
> But _does_ anyone have any better solutions?

This patch might not be needed at all, as per Kristen's recent comments
on the linux-pci mailing list, and her small patch that is already in
the -mm tree.

I'll let the discussion continue on that list.

thanks,

greg k-h