High CPU usage from NetworkManager with QCNCM865 (WCN7850)

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Hi, I'm experiencing a reproducible issue with the ath12k driver when 
using a QCNCM865 Wi-Fi card based on the WCN7850 chipset.

After boot, everything works normally, NetworkManager shows 0-3% CPU 
usage. However, if I toggle Wi-Fi off and on (using rfkill block/unblock 
wlan), NetworkManager begins consuming 100% of a CPU core and stays at 
full usage indefinitely, until Wi-Fi is turned off again. This is fully 
reproducible on my system.

There are no relevant logs in `journalctl -u NetworkManager`, and the 
memory usage remains low. Only one thread in NetworkManager is affected. 
Disabling Wi-Fi immediately returns CPU usage to 0%.

Here is my system info:

- Wi-Fi card: QCNCM865 (WCN7850)
- Distro: Arch Linux
- Kernel: linux 6.16 latest commit from torvald's tree : 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7d4e49a77d9930c69751b9192448fda6ff9100f1
- Firmware version: 
WLAN.HMT.1.1.c5-00284.1-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3 (I also tried 
the old firmware, same issue)

Relevant dmesg output:

[    5.705423] ath12k_pci 0000:c0:00.0: BAR 0 [mem 0xb0600000-0xb07fffff 
64bit]: assigned
[    5.705440] ath12k_pci 0000:c0:00.0: enabling device (0000 -> 0002)
[    5.705877] ath12k_pci 0000:c0:00.0: MSI vectors: 16
[    5.705887] ath12k_pci 0000:c0:00.0: Hardware name: wcn7850 hw2.0
[    6.230762] ath12k_pci 0000:c0:00.0: chip_id 0x2 chip_family 0x4 
board_id 0xff soc_id 0x40170200
[    6.230774] ath12k_pci 0000:c0:00.0: fw_version 0x1108811c 
fw_build_timestamp 2025-05-17 00:21 fw_build_id 
QC_IMAGE_VERSION_STRING=WLAN.HMT.1.1.c5-00284.1-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3 

[    6.231110] ath12k_pci 0000:c0:00.0: failed to get ACPI BDF EXT: 0
[   14.038268] ath12k_pci 0000:c0:00.0: Failed to set the requested 
Country regulatory setting
[   14.038525] ath12k_pci 0000:c0:00.0: Failed to set the requested 
Country regulatory setting
[  194.622322] ath12k_pci 0000:c0:00.0: failed to enqueue rx buf: -28
[ 1400.638540] ath12k_pci 0000:c0:00.0: failed to enqueue rx buf: -28

<info>  [1748767795.5349] policy: set 'REDACTED' (wlan0) as default for 
IPv4 routing and DNS
<info>  [1748767801.5408] device (wlan0): state change: ip-config -> 
ip-check (reason 'none', managed-type: 'full')
<info>  [1748767801.5420] device (wlan0): state change: ip-check -> 
secondaries (reason 'none', managed-type: 'full')
<info>  [1748767801.5421] device (wlan0): state change: secondaries -> 
activated (reason 'none', managed-type: 'full')
<info>  [1748767801.5423] manager: NetworkManager state is now 
CONNECTED_SITE
<info>  [1748767801.5424] device (wlan0): Activation: successful, device 
activated.
<info>  [1748767804.6745] manager: NetworkManager state is now 
CONNECTED_GLOBAL
<info>  [1748767804.6842] dhcp6 (wlan0): activation: beginning 
transaction (timeout in 45 seconds)
<info>  [1748767804.6846] policy: set 'REDACTED' (wlan0) as default for 
IPv6 routing and DNS
<info>  [1748767804.6940] dhcp6 (wlan0): state changed new lease

event: disconnect-info, reason: 3
event: state, old: connected, new: disconnected
event: state, old: disconnected, new: autoconnect_quick
event: state, old: autoconnect_quick, new: autoconnect_full
Received error during CMD_TRIGGER_SCAN: Network is down (100)
event: state, old: disconnected, new: autoconnect_quick
event: connect-info, ssid: REDACTED, bss: RE:DA:CT:ED, signal: -22, 
load: 5/255
event: state, old: autoconnect_quick, new: connecting (auto)
event: state, old: connecting (auto), new: connected


Additional notes:

- The issue only occurs after toggling Wi-Fi; it does not happen 
immediately after boot.
- Disabling Wi-Fi instantly stops the CPU usage spike.
- No errors are visible in NetworkManager logs, but it clearly enters a 
tight loop after Wi-Fi state changes.
- I suspect this might be a bug in ath12k or its interaction with iwd or 
NetworkManager, possibly related to buffer handling or background scanning.

Please let me know if there's anything I can do to help debug this, I 
can provide more logs, test patches, or try different firmware versions 
if needed.

Thanks