Re: [PATCH] pci: Added flag to pci_host_bridge to hint not to use acpi

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Apr 07, 2016 at 02:12:16PM -0600, Jon Derrick wrote:
> Hi Bjorn,
> 
> First, thanks for the review
> 
> > The spec (PCI Firmware spec 3.0, sec 4.5) says _OSC is a child of an
> > ACPI device and applies to that device.  In your case, I think there
> > is no ACPI PNP0A0x device for the VMD host bridge, and hence there is
> > no _OSC method for it.  There's no ACPI handle for the VMD bridge, so
> > I think pcie_port_acpi_setup() returns -EINVAL, which causes
> > get_port_device_capability() to give up and decide that the port
> > can't support *any* PCIe services.
> > 
> > I think that's the real problem: the fact that there's no ACPI device
> > corresponding to the bridge should not be an error.  It should just
> > mean the platform doesn't have an opportunity to limit what services
> > the kernel can manage.  I think pcie_port_acpi_setup() should return 0
> > in all cases.  Can you try that and see if it fixes the problem?
> > 
> 
> I believe what you are suggesting is:
> 
> 
>         handle = acpi_find_root_bridge_handle(port);
>         if (!handle)
> -               return -EINVAL;
> +               return 0;
> 
>         root = acpi_pci_find_root(handle);
>         if (!root)
> -               return -ENODEV;
> +               return 0;

Yes, that's what I think we should do.

Bjorn