Re: [PATCH v8 1/5] PCI: Conditionally initialize host bridge native_* members

[Kuppuswamy, Sathyanarayanan]

On 9/10/20 2:00 PM, Kuppuswamy, Sathyanarayanan wrote:
> On 9/10/20 12:49 PM, Bjorn Helgaas wrote:
> > On Fri, Jul 24, 2020 at 08:58:52PM -0700, sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx wrote:
> > > From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> > >
> > > If CONFIG_PCIEPORTBUS is not enabled in kernel then initialing
> > > struct pci_host_bridge PCIe specific native_* members to "1" is
> > > incorrect. So protect the PCIe specific member initialization
> > > with CONFIG_PCIEPORTBUS.
> >
> > s/initialing/initializing/
> will fix it in next version.
> > > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> > > ---
> > >   drivers/pci/probe.c | 4 +++-
> > >   1 file changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > > index 2f66988cea25..a94b97564ceb 100644
> > > --- a/drivers/pci/probe.c
> > > +++ b/drivers/pci/probe.c
> > > @@ -588,12 +588,14 @@ static void pci_init_host_bridge(struct pci_host_bridge *bridge)
> > >        * may implement its own AER handling and use _OSC to prevent the
> > >        * OS from interfering.
> > >        */
> > > +#ifdef CONFIG_PCIEPORTBUS
> > >       bridge->native_aer = 1;
> > >       bridge->native_pcie_hotplug = 1;
> > > -    bridge->native_shpc_hotplug = 1;
> > >       bridge->native_pme = 1;
> > >       bridge->native_ltr = 1;
> >
> > native_ltr isn't dependent on PCIEPORTBUS either, is it?  It's only
> > used for ASPM.
> Agreed. I was confused due to a comment in include/linux/pci.h
>
>   unsigned int    native_ltr:1;           /* OS may use PCIe LTR */
Currently there is no code dependency between LTR and CONFIG_PCIEPORTBUS.

But I am wondering whether its correct to move LTR code under
CONFIG_PCIEPORTBUS?. As per PCIe spec v5.0 sec 7.8.2, LTR is a optional
PCIe extended capability. So why is not moved under drivers/pci/pcie/*. What is
the criteria for code to be placed under drivers/pci/pcie/*
> > >       bridge->native_dpc = 1;
> > > +#endif
> > > +    bridge->native_shpc_hotplug = 1;
> > >       device_initialize(&bridge->dev);
> > >   }
> > > --
> > > 2.17.1

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer