BUG: spinlock bad magic on CPU#1, irq/39-firewire/245 (v6.18-rc4, ppc64)

Greetings!

Getting this on my PowerMac G5 11,2 at boot on kernel 6.18-rc4:

[...]
firewire_ohci 0001:03:0e.0: added OHCI v1.0 device as card 0, 8 IR + 8 
IT contexts, quirks 0x0
BUG: spinlock bad magic on CPU#1, irq/39-firewire/245
  lock: 0xc00000001f672618, .magic: 00000000, .owner: 
irq/39-firewire/245, .owner_cpu: 1
CPU: 1 UID: 0 PID: 245 Comm: irq/39-firewire Tainted: G 
N  6.18.0-rc4-PMacG5 #1 PREEMPTLAZY
Tainted: [N]=TEST
Hardware name: PowerMac11,2 PPC970MP 0x440101 PowerMac
Call Trace:
[c000000005dafb20] [c000000000bc054c] __dump_stack+0x30/0x54 (unreliable)
[c000000005dafb50] [c000000000bc04e4] dump_stack_lvl+0x98/0xd0
[c000000005dafb90] [c0000000000f22a8] spin_dump+0x88/0xb4
[c000000005dafc10] [c0000000000f1d4c] do_raw_spin_unlock+0xdc/0x164
[c000000005dafc50] [c000000000bf65d0] _raw_spin_unlock+0x18/0x68
[c000000005dafc70] [c0003d0013ce1d5c] 
fw_core_handle_bus_reset+0xa98/0xb64 [firewire_core]
[c000000005dafdc0] [c0003d0013d19aec] 
handle_selfid_complete_event+0x610/0x764 [firewire_ohci]
[c000000005dafe80] [c000000000106050] irq_thread_fn+0x40/0x9c
[c000000005dafec0] [c000000000105ecc] irq_thread+0x1c0/0x298
[c000000005daff60] [c0000000000b5e54] kthread+0x250/0x280
[c000000005daffe0] [c00000000000bd30] start_kernel_thread+0x14/0x18

This is reproducible and happens every time at boot.

The firewire controller in question is the G5s' onboard one:

  # lspci -s 0001:03:0e.0 -vv
0001:03:0e.0 FireWire (IEEE 1394): Apple Inc. Shasta Firewire (prog-if 
10 [OHCI])
	Subsystem: Apple Inc. Device 5811
	Device tree node: 
/sys/firmware/devicetree/base/ht@0,f2000000/pci@9/firewire@e
	Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- 
<TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 248 (3000ns min, 6000ns max), Cache Line Size: 64 bytes
	Interrupt: pin A routed to IRQ 39
	Region 0: Memory at fa400000 (32-bit, non-prefetchable) [size=4K]
	Capabilities: [44] Power Management version 2
		Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA PME(D0+,D1+,D2+,D3hot+,D3cold-)
		Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME+
	Kernel driver in use: firewire_ohci
	Kernel modules: firewire_ohci


Kernel .config attached. Full dmesg available at request.

Regards,
Erhard