On Wed, Mar 20, 2024 at 6:31 AM Christian König <ckoenig.leichtzumerken@xxxxxxxxx> wrote: > Can you provide the full output of lspci -vvvv. As far as I can see that doesn't looks so invalid to me. I've added the relevant pci probing debug output without assign-busses and the lspci -vvvv for a boot with all devices visible. https://gist.github.com/kkartaltepe/2f01f33c7e7af33cf0d28678e91f50fb > Well that is just a very very old workaround for a buggy BIOS on 20 year old laptops. The last reference I could find for hardware which actually needed it is this: > > commit 8c4b2cf9af9b4ecc29d4f0ec4ecc8e94dc4432d7 > Author: Bernhard Kaindl <bk@xxxxxxx> > Date: Sat Feb 18 01:36:55 2006 -0800 > > [PATCH] PCI: PCI/Cardbus cards hidden, needs pci=assign-busses to fix > > > So as far as I know nobody had to use that in ages and I wouldn't expect that this option actually works correctly on any modern hardware. > > Especially not anything PCIe based since it messes up the ACPI to PCIe device mappings. That amdgpu doesn't work is just the tip of the iceberg here. > > The bus assignment code in the PCI subsystem is made to support hotplug, not completely re-number the root hubs from scratch. That is just a hack somebody came up with two decades ago to get some Cardbus slots in laptops working. > > I'm not sure yet what's going wrong with the Thunderbold controller, but completely re-assigning bus numbers is certainly the wrong approach. I was referring to the work outlined in https://ostconf.com/system/attachments/files/000/001/698/original/Sergei_Miroshnichenko_linux_piter_2019_presentation.pdf?1570136708 for nvme enclosures. Which maybe referncing more the movable BARs than the renumbering that occurs with assign-busses, but also on power with device trees which may behave differently as it mentions assign-busses to get this same renumbering of buses. This makes me think at least modern non-x86 devices expect to behave this way, which may not be relevant to ACPI/x86 systems but at least this shared pci code should be solid. > I'm not sure yet what's going wrong with the Thunderbold controller, but completely re-assigning bus numbers is certainly the wrong approach. I agree, it is just what is currently available in the kernel. A less disruptive approach seems needed. --Kurt Kartaltepe
