BAR resizing broken in 6.18 (PPC only?)

[Manivannan Sadhasivam]

+ Ilpo

On Thu, Oct 16, 2025 at 12:08:46PM +0900, Simon Richter wrote:
> Hi,
> 
> since switching to 6.18rc1, I get
> 
> xe 0030:03:00.0: enabling device (0140 -> 0142)
> xe 0030:03:00.0: [drm] unbounded parent pci bridge, device won't support any
> PM support.
> xe 0030:03:00.0: [drm] Attempting to resize bar from 256MiB -> 16384MiB
> xe 0030:03:00.0: BAR 0 [mem 0x620c000000000-0x620c000ffffff 64bit]:
> releasing
> xe 0030:03:00.0: BAR 2 [mem 0x6200000000000-0x620000fffffff 64bit pref]:
> releasing
> pci 0030:02:01.0: bridge window [mem 0x6200000000000-0x620001fffffff 64bit
> pref]: releasing
> pci 0030:01:00.0: bridge window [mem 0x6200000000000-0x6203fbff0ffff 64bit
> pref]: releasing
> pci 0030:00:00.0: bridge window [mem 0x6200000000000-0x6203fbff0ffff 64bit
> pref]: was not released (still contains assigned resources)
> pci 0030:02:01.0: disabling bridge window [io  0x0000-0xffffffffffffffff
> disabled] to [bus 03] (unused)
> pci 0030:02:02.0: disabling bridge window [io  0x0000-0xffffffffffffffff
> disabled] to [bus 04] (unused)
> pci 0030:02:02.0: disabling bridge window [mem 0x00000000-0xffffffffffffffff
> 64bit pref disabled] to [bus 04] (unused)
> pci 0030:01:00.0: disabling bridge window [io  0x0000-0xffffffffffffffff
> disabled] to [bus 02-04] (unused)
> pci 0030:00:00.0: Assigned bridge window [mem
> 0x6200000000000-0x6203fbff0ffff 64bit pref] to [bus 01-04] cannot fit
> 0x4000000000 required for 0030:01:00.0 bridging to [bus 02-04]
> pci 0030:01:00.0: bridge window [mem size 0x3fc0000000 64bit pref] to [bus
> 02-04] requires relaxed alignment rules
> pci 0030:00:00.0: disabling bridge window [io  0x0000-0xffffffffffffffff
> disabled] to [bus 01-04] (unused)
> pci 0030:01:00.0: bridge window [mem size 0x3fc0000000 64bit pref]: can't
> assign; no space
> pci 0030:01:00.0: bridge window [mem size 0x3fc0000000 64bit pref]: failed
> to assign
> pci 0030:01:00.0: bridge window [mem size 0x3fc0000000 64bit pref]: can't
> assign; no space
> pci 0030:01:00.0: bridge window [mem size 0x3fc0000000 64bit pref]: failed
> to assign
> pci 0030:02:01.0: bridge window [mem size 0x400000000 64bit pref]: can't
> assign; no space
> pci 0030:02:01.0: bridge window [mem size 0x400000000 64bit pref]: failed to
> assign
> pci 0030:02:01.0: bridge window [mem size 0x400000000 64bit pref]: can't
> assign; no space
> pci 0030:02:01.0: bridge window [mem size 0x400000000 64bit pref]: failed to
> assign
> xe 0030:03:00.0: BAR 2 [mem size 0x400000000 64bit pref]: can't assign; no
> space
> xe 0030:03:00.0: BAR 2 [mem size 0x400000000 64bit pref]: failed to assign
> xe 0030:03:00.0: BAR 0 [mem 0x620c000000000-0x620c000ffffff 64bit]: assigned
> xe 0030:03:00.0: BAR 0 [mem 0x620c000000000-0x620c000ffffff 64bit]:
> releasing
> xe 0030:03:00.0: BAR 2 [mem size 0x400000000 64bit pref]: can't assign; no
> space
> xe 0030:03:00.0: BAR 2 [mem size 0x400000000 64bit pref]: failed to assign
> xe 0030:03:00.0: BAR 0 [mem 0x620c000000000-0x620c000ffffff 64bit]: assigned
> pci 0030:00:00.0: PCI bridge to [bus 01-04]
> pci 0030:00:00.0:   bridge window [mem 0x620c000000000-0x620c07fefffff]
> pci 0030:00:00.0:   bridge window [mem 0x6200000000000-0x6203fbff0ffff 64bit
> pref]
> pci 0030:01:00.0: bridge window [mem 0x6200000000000-0x6203fbff0ffff 64bit
> pref]: can't claim; address conflict with 0030:01:00.0 [mem
> 0x6200020000000-0x62000207fffff 64bit pref]
> pci 0030:01:00.0: PCI bridge to [bus 02-04]
> pci 0030:01:00.0:   bridge window [mem 0x620c000000000-0x620c07fefffff]
> pci 0030:02:01.0: bridge window [mem 0x6200000000000-0x620001fffffff 64bit
> pref]: can't claim; no compatible bridge window
> pci 0030:02:01.0: PCI bridge to [bus 03]
> pci 0030:02:01.0:   bridge window [mem 0x620c000000000-0x620c0013fffff]
> xe 0030:03:00.0: [drm] Failed to resize BAR2 to 16384M (-ENOSPC). Consider
> enabling 'Resizable BAR' support in your BIOS
> xe 0030:03:00.0: BAR 2 [mem size 0x10000000 64bit pref]: can't assign; no
> space
> xe 0030:03:00.0: BAR 2 [mem size 0x10000000 64bit pref]: failed to assign
> xe 0030:03:00.0: BAR 2 [mem size 0x10000000 64bit pref]: can't assign; no
> space
> xe 0030:03:00.0: BAR 2 [mem size 0x10000000 64bit pref]: failed to assign
> xe 0030:03:00.0: [drm] Found battlemage (device ID e20b) discrete display
> version 14.01 stepping B0
> xe 0030:03:00.0: [drm] *ERROR* pci resource is not valid
> 
> There's also a bug report[1] on the freedesktop GitLab, but this may be a
> more generic problem.
> 
> I'm unsure what other "assigned resources" would be below the root that are
> not covered by the bridge window of equal size on the upstream port of the
> GPU -- also it would be really cool if it reverted to the old state on
> failure instead of creating an invalid configuration.
> 
> Also, why do we change the BAR assignment while mem decoding is active?
> 

This could be due to the recently merged patch that changes the way we read
bridge resources. We saw a similar bug report with Qcom platforms as well [1].a43ac325c7cb

Could you please try reverting the below mentioned commit and see if that fixes
the issue?

a43ac325c7cb ("PCI: Set up bridge resources earlier")

- Mani

[1] https://lore.kernel.org/lkml/017ff8df-511c-4da8-b3cf-edf2cb7f1a67@packett.cool

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