Messages in this thread | | | From | Nicholas Johnson <> | Subject | Re: [[RFC PATCH v1] 1/1] PCI: Add pci=nobbn to ignore ACPI _BBN method to override host bridge bus window | Date | Fri, 17 Jan 2020 15:00:11 +0000 |
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On Thu, Jan 16, 2020 at 11:13:13PM +0100, Thomas Gleixner wrote: > Nicholas, > > Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au> writes: > > > Add pci=nobbn kernel parameter. > > > > Override the host bridge bus resource to [bus 00-ff] when specified. > > Fine, but you completely fail to explain why this is useful and why > someone would utilize this command line parameter. There are motherboards with single PCIe root complex which give significantly less than [bus 00-ff] via CRS. I own one with [bus 00-7f] and have seen some with significantly less.
A user who wants to use more busses than the motherboard advertises will want to use this kernel parameter, for instance if they have a lot of PCIe switches or Thunderbolt 3 devices.
This is similar to how we have pci=nocrs to override motherboards with issues. The bus resource is not overridden by pci=nocrs, even though it will usually come from the same method. However, I believe it would be unwise to change pci=nocrs to include bus resource, as detailed in my original RFC.
> > Thanks, > > tglx
Thanks, Nicholas
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