[PATCH 3/5] Float the pci bus number on MPC8641HPCN board.

[Zhang Wei-r63237]

Hi, Wade,

That's a good question.

The ppc_md.exclude_device() function will be called before PCI config
access in indirect_read/write_config() of the file
arch/powerpc/sysdev/indirect_pci.c. If the hose->bus_offset value is 0,
the primary bus number register of the host must be hose->first_busno.
Otherwise, if the host primary bus number register is 0, the
hose->bus_offset must be the same value of hose->first_buseno.

When the pci scan bus, the bridge will be scaned twice. When the second
scan is finished, the host primary bus number register will be write to
hose->first_busno. The PCI bus(not the first PCI host) access will be
wrong in the later access. I'll check it and correct the
hose->bus_offset value in these codes.

Thanks!
Wei

> -----Original Message-----
> From: Wade Farnsworth [mailto:wfarnsworth at mvista.com] 
> Subject: Re: [PATCH 3/5] Float the pci bus number on 
> MPC8641HPCN board.
> 
> On Tue, 2007-05-22 at 11:38 +0800, Zhang Wei wrote:
> >  int mpc86xx_exclude_device(u_char bus, u_char devfn)
> >  {
> > +	struct pci_controller *hose;
> > +
> > +	hose = pci_bus_to_hose(bus);
> > +	if (unlikely(!hose))
> > +		return PCIBIOS_DEVICE_NOT_FOUND;
> > +
> > +	/* Correcting the hose->bus_offset value. */
> > +	out_be32(hose->cfg_addr, 0x80000000 | ((hose->first_busno
> > +					- hose->bus_offset) << 16));
> > +	if (unlikely(in_le32(hose->cfg_data) == 0xffffffff))
> > +		hose->bus_offset = hose->bus_offset ? 0 : 
> hose->first_busno;
> > +
> >  	return PCIBIOS_SUCCESSFUL;
> >  }
> 
> What is the purpose of this code and why put it in
> mpc86xx_exclude_device?
> 
> --Wade
> 
>