[Skiboot] [PATCH 16/33] pci: When restoring bus numbers after a reset, also restore device cache

[Benjamin Herrenschmidt]

On Wed, 2016-07-06 at 17:24 +1000, Michael Neuling wrote:
> On Sat, 2016-06-25 at 08:47 +1000, Benjamin Herrenschmidt wrote:
> > PCIe devices cache the bus number on the first config write, make
> > sure
> > we restore them when at the same time
> 
> Is this a fix that needs to go into some stable builds?

Yes probably, not a huge issue though.

> > Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> > 
> > ---
> >  core/pci.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/core/pci.c b/core/pci.c
> > index 9b65a49..7ba5169 100644
> > --- a/core/pci.c
> > +++ b/core/pci.c
> > @@ -1605,8 +1605,14 @@ static int __pci_restore_bridge_buses(struct
> > phb *phb,
> >  				      struct pci_device *pd,
> >  				      void *data __unused)
> >  {
> > -	if (!pd->is_bridge)
> > +	if (!pd->is_bridge) {
> > +		uint32_t vdid;
> > +
> > +		/* Make all devices below a bridge "re-capture"
> > the bdfn */
> > +		if (pci_cfg_read32(phb, pd->bdfn, 0, &vdid) == 0)
> > +			pci_cfg_write32(phb, pd->bdfn, 0, vdid);
> 
> Do we have a lock held here to ensure there is no race?

No no need. The register is read only, the write does nothing other
than making the device capture it's own bus ID from the packet.

> >  		return 0;
> > +	}
> >  
> >  	pci_cfg_write8(phb, pd->bdfn, PCI_CFG_PRIMARY_BUS,
> >  		       pd->primary_bus);