Re: [PATCH] PCI: Make pcie_find_root_port() work for PCIe root ports as well

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Tue, Jun 30, 2020 at 05:01:07PM -0500, Bjorn Helgaas wrote:
> On Mon, Jun 22, 2020 at 07:12:48PM +0300, Mika Westerberg wrote:
> > Commit 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and
> > pci_find_pcie_root_port()") unified the root port finding functionality
> > into a single function but missed the fact that the passed in device may
> > already be a root port. This causes the kernel to block power management
> > of PCIe hierarchies in recent systems because ->bridge_d3 started to
> > return false for such ports after the commit in question.
> > 
> > Fixes: 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and pci_find_pcie_root_port()")
> > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> > Cc: stable@vger.kernel.org
> > ---
> >  include/linux/pci.h | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index c79d83304e52..c17c24f5eeed 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -2169,8 +2169,13 @@ static inline int pci_pcie_type(const struct pci_dev *dev)
> >   */
> >  static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
> >  {
> > -	struct pci_dev *bridge = pci_upstream_bridge(dev);
> > +	struct pci_dev *bridge;
> >  
> > +	/* If dev is already root port */
> > +	if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
> > +		return dev;
> > +
> > +	bridge = pci_upstream_bridge(dev);
> >  	while (bridge) {
> >  		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
> >  			return bridge;
> 
> I applied the patch below, which is slightly simplified but I think
> still equivalent, to for-linus for v5.8.  Let me know if it's not.

Thanks I just tested and it also works fine.

> I dropped the stable tag because 6ae72bfa656e was merged for v5.8-rc1,
> and I assume v5.7 works correctly so it doesn't need any change.

Right, makes sense.