On 5/30/25 3:48 PM, Ilpo Järvinen wrote: >>> I added the suggested prints >>> (https://paste.ofcode.org/DgmZGGgS6D36nWEzmfCqMm) on top of v6.15 with >>> the downstream PCIe pixel driver and I obtain the following. Note that >>> all added prints contain "tudor" for differentiation. >>> >>> [ 15.211179][ T1107] pci 0001:01:00.0: [144d:a5a5] type 00 class >>> 0x000000 PCIe Endpoint >>> [ 15.212248][ T1107] pci 0001:01:00.0: BAR 0 [mem >>> 0x00000000-0x000fffff 64bit] >>> [ 15.212775][ T1107] pci 0001:01:00.0: ROM [mem 0x00000000-0x0000ffff >>> pref] >>> [ 15.213195][ T1107] pci 0001:01:00.0: enabling Extended Tags >>> [ 15.213720][ T1107] pci 0001:01:00.0: PME# supported from D0 D3hot >>> D3cold >>> [ 15.214035][ T1107] pci 0001:01:00.0: 15.752 Gb/s available PCIe >>> bandwidth, limited by 8.0 GT/s PCIe x2 link at 0001:00:00.0 (capable of >>> 31.506 Gb/s with 16.0 GT/s PCIe x2 link) >>> [ 15.222286][ T1107] pci 0001:01:00.0: tudor: 1: pbus_size_mem: BAR 0 >>> [mem 0x00000000-0x000fffff 64bit] list empty? 1 >>> [ 15.222813][ T1107] pci 0001:01:00.0: tudor: 1: pbus_size_mem: ROM >>> [mem 0x00000000-0x0000ffff pref] list empty? 1 >>> [ 15.224429][ T1107] pci 0001:01:00.0: tudor: 2: pbus_size_mem: ROM >>> [mem 0x00000000-0x0000ffff pref] list empty? 0 >>> [ 15.224750][ T1107] pcieport 0001:00:00.0: bridge window [mem >>> 0x00100000-0x001fffff] to [bus 01-ff] add_size 100000 add_align 100000 >>> >>> [ 15.225393][ T1107] tudor : pci_assign_unassigned_bus_resources: >>> before __pci_bus_assign_resources -> list empty? 0 >>> [ 15.225594][ T1107] pcieport 0001:00:00.0: tudor: >>> pdev_sort_resources: bridge window [mem 0x00100000-0x001fffff] resource >>> added in head list >>> [ 15.226078][ T1107] pcieport 0001:00:00.0: bridge window [mem >>> 0x40000000-0x401fffff]: assigned >> So here it ends up assigning the resource here I think. >> >> >> That print isn't one of yours in reassign_resources_sorted() so the >> assignment must have been made in assign_requested_resources_sorted(). But >> then nothing is printed out from reassign_resources_sorted() so I suspect >> __assign_resources_sorted() has short-circuited. >> >> We know that realloc_head is not empty, so that leaves the goto out from >> if (list_empty(&local_fail_head)), which kind of makes sense, all >> entries on the head list were assigned. But the code there tries to remove >> all head list resources from realloc_head so why it doesn't get removed is >> still a mystery. assign_requested_resources_sorted() doesn't seem to >> remove anything from the head list so that resource should still be on the >> head list AFAICT so it should call that remove_from_list(realloc_head, >> dev_res->res) for it. >> >> So can you see if that theory holds water and it short-circuits without >> removing the entry from realloc_head? > I think I figured out more about the reason. It's not related to that > bridge window resource. > > pbus_size_mem() will add also that ROM resource into realloc_head > as it is considered (intentionally) optional after the optional change > (as per "tudor: 2:" line). And that resource is never assigned because right, the ROM resource is added into realloc_head here: https://web.git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/pci/setup-bus.c#n1202 Then in the failing case, and extra resource is added: [ 15.224750][ T1107] pcieport 0001:00:00.0: bridge window [mem 0x00100000-0x001fffff] to [bus 01-ff] add_size 100000 add_align 100000 The above extra print happens just in the failing case. Here's where the extra resource is added: https://web.git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/pci/setup-bus.c#n1285 It seems that in the failing case 2 resources are added into realloc_head at the pbus_size_mem() time, whereas with the patch reverted - none. Also, in the failing case a smaller resource is added into the list: pdev_sort_resources: bridge window [mem 0x00100000-0x001fffff] compared to the working case: pdev_sort_resources: bridge window [mem 0x00100000-0x002fffff] Can this make a difference? > pdev_sort_resources() didn't pick it up into the head list. The next > question is why the ROM resource isn't in the head list. > It seems the ROM resource is skipped at: https://web.git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/pci/setup-bus.c#n175 tudor: pdev_sort_resources: ROM [??? 0x00000000 flags 0x0] resource skipped due to !(r->flags) || r->parent > > While it is not necessarily related to issue, I think the bridge sizing > functions too should consider pdev_resources_assignable() so that it > won't ever add resources from such devices onto the realloc_head. This is > yet another small inconsistency within all this fitting/assignment logic. > > pbus_size_mem() seems to consider IORESOURCE_PCI_FIXED so that cannot > explain it as the ROM resource wouldn't be on the realloc_head list in > that case. > > > Just wanted to let you know early even if I don't fully understand > everything so you can hopefully avoid unnecessary debugging. Thanks! Would adding some prints in pbus_size_mem() to describe the code paths in the working and non-working case help? Cheers, ta
