Re: clarification: PCI device not getting enumerated

[Ratheesh Kannoth]

On 2026-03-18 at 09:30:58, Ratheesh Kannoth (rkannoth@xxxxxxxxxxx) wrote:
> On 2026-03-18 at 02:36:40, Bjorn Helgaas (helgaas@xxxxxxxxxx) wrote:
> > > Hi,
> > >
> > > Below commit breaks PCI enumeration of a marvell PCI endpoint (177d:a0e2).
> > > I am not familiar with PCI code, could you please help in debugging/fixing this ?
> > >
> > > Before the commit, the kernel set PCI_REASSIGN_ALL_BUS. So pcibios_assign_all_busses() was true,
> > > and in pci_scan_bridge_extend() the kernel took the “reassign” path and used EA
> > > (and pci_ea_fixed_busnrs()) to assign bus numbers.
> > >
> > > commit 7246a4520b4bf1494d7d030166a11b5226f6d508
> > > Author: Vidya Sagar <vidyas@xxxxxxxxxx>
> > > Date:   Wed May 8 23:11:38 2024 +0530
> > >
> > >     PCI: Use preserve_config in place of pci_flags
> > >
> > >     Use preserve_config in place of checking for PCI_PROBE_ONLY flag to enable
> > >     support for "linux,pci-probe-only" on a per host bridge basis.
> > >
> > >     This also obviates the use of adding PCI_REASSIGN_ALL_BUS flag if
> > >     !PCI_PROBE_ONLY, as pci_assign_unassigned_root_bus_resources() takes care
> > >     of reassigning the resources that are not already claimed.
> >
> > This commit appeared in v6.11.  Apparently on v6.6, 0002:1b:00.0 is
> > detected, and in the v6.12 dmesg below, we don't enumerate it.
> >
> > It looks like 7246a4520b4b can still be reverted cleanly from
> > v7.0-rc1.  Can you collect the complete dmesg logs from v7.0-rc1
> > (where I assume we won't see 0002:1b:00.0) and from v7.0-rc1 with
> > 7246a4520b4b reverted (where I assume we *will* see it) and output of
> > "sudo lspci -vv"?  Use the same kernel config and DT for both, of
> > course.
> Please find dmesg, lspci -vv and device tree output for v7.0-rc1 and v7.0-rc1 with patch reverted
> at bottom of this email. Used same kernel config and DT for both.
Sorry to bother.

Could you please advise on the preferred approach to address this issue? Alternatively, if further
testing or additional data would be helpful, I would be happy to carry that out and share the results.

Thanks a ton for your time !