Re: [PATCH] PCI: Use pci_is_root_bus() to check for root bus

[Bjorn Helgaas <bhelgaas@google.com>]

On Wed, Nov 06, 2013 at 04:28:48PM -0800, Yinghai Lu wrote:
> On Wed, Nov 6, 2013 at 12:46 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> 
> > Oh, I see.  The problem is when VF is on a virtual bus and the
> > corresponding PF is on a root bus.  Then we have:
> >
> >   pci_is_root_bus(VF) == false
> >   pci_upstream_bridge(VF) == pci_upstream_bridge(PF)
> >   pci_uptream_bridge(PF) == NULL
> >
> > I guess that's what your suggestion about "caching the return from
> > pci_upstream_bridge()" was about.  Like this:
> 
> Yes.
> 
> For the two patches,
> 
> Acked-by: Yinghai Lu <yinghai@kernel.org>

Thanks, I applied these two with your acks to my pci/misc branch for
v3.13.

Bjorn

> >
> > commit 21ea57bf1311f7a8d1b755d355322a1f077fccb7
> > Author: Bjorn Helgaas <bhelgaas@google.com>
> > Date:   Wed Nov 6 10:11:48 2013 -0700
> >
> >     PCI: Add pci_upstream_bridge()
> >
> >     This adds a pci_upstream_bridge() interface to find the PCI-to-PCI bridge
> >     upstream from a device.  This is typically just "dev->bus->self", but in
> >     the case of a VF on a virtual bus, we have to start from the corresponding
> >     PF.  Returns NULL if there is no upstream PCI bridge, i.e., if the device
> >     is on a root bus.
> >
> >     Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> >
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index d3a888a..835ec7b 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -480,6 +480,15 @@ static inline bool pci_is_root_bus(struct pci_bus *pbus)
> >         return !(pbus->parent);
> >  }
> >
> > +static inline struct pci_dev *pci_upstream_bridge(struct pci_dev *dev)
> > +{
> > +       dev = pci_physfn(dev);
> > +       if (pci_is_root_bus(dev->bus))
> > +               return NULL;
> > +
> > +       return dev->bus->self;
> > +}
> > +
> >  #ifdef CONFIG_PCI_MSI
> >  static inline bool pci_dev_msi_enabled(struct pci_dev *pci_dev)
> >  {
> > commit bca690ab580d5c0c4a0c7201f3c42057288add8b
> > Author: Bjorn Helgaas <bhelgaas@google.com>
> > Date:   Wed Nov 6 10:00:51 2013 -0700
> >
> >     PCI: Enable upstream bridges even for VFs on virtual buses
> >
> >     Previously we enabled the upstream PCI-to-PCI bridge only when
> >     "dev->bus->self != NULL".  In the case of a VF on a virtual bus, where
> >     "bus->self == NULL", we didn't enable the upstream bridge.
> >
> >     This fixes that by enabling the upstream bridge of the PF corresponding to
> >     the VF.
> >
> >     Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> >
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index ac40f90..d3ed931 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -1148,12 +1148,12 @@ int pci_reenable_device(struct pci_dev *dev)
> >
> >  static void pci_enable_bridge(struct pci_dev *dev)
> >  {
> > +       struct pci_dev *bridge;
> >         int retval;
> >
> > -       if (!dev)
> > -               return;
> > -
> > -       pci_enable_bridge(dev->bus->self);
> > +       bridge = pci_upstream_bridge(dev);
> > +       if (bridge)
> > +               pci_enable_bridge(bridge);
> >
> >         if (pci_is_enabled(dev)) {
> >                 if (!dev->is_busmaster)
> > @@ -1170,6 +1170,7 @@ static void pci_enable_bridge(struct pci_dev *dev)
> >
> >  static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
> >  {
> > +       struct pci_dev *bridge;
> >         int err;
> >         int i, bars = 0;
> >
> > @@ -1188,7 +1189,9 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
> >         if (atomic_inc_return(&dev->enable_cnt) > 1)
> >                 return 0;               /* already enabled */
> >
> > -       pci_enable_bridge(dev->bus->self);
> > +       bridge = pci_upstream_bridge(dev);
> > +       if (bridge)
> > +               pci_enable_bridge(bridge);
> >
> >         /* only skip sriov related */
> >         for (i = 0; i <= PCI_ROM_RESOURCE; i++)