[Bug 2138754] Re: [ath12k wcn7850] 5 GHz Wi-Fi broken in kernel 6.17+ due to broken frequency range filtering

Hello Saikiran, or anyone else affected,

Accepted linux-firmware into questing-proposed. The package will build
now and be available at https://launchpad.net/ubuntu/+source/linux-
firmware/20250901.git993ff19b-0ubuntu1.8 in a few hours, and then in the
-proposed repository.

Please help us by testing this new package. See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed. Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
questing to verification-done-questing. If it does not fix the bug for
you, please add a comment stating that, and change the tag to
verification-failed-questing. In either case, without details of your
testing we will not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: linux-firmware (Ubuntu)
Status: New => Fix Released

** Changed in: linux-firmware (Ubuntu Questing)
Status: In Progress => Fix Committed

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https://bugs.launchpad.net/bugs/2138754

Title:
[ath12k wcn7850] 5 GHz Wi-Fi broken in kernel 6.17+ due to broken
frequency range filtering

Status in linux package in Ubuntu:
Invalid
Status in linux-firmware package in Ubuntu:
Fix Released
Status in linux source package in Questing:
Invalid
Status in linux-firmware source package in Questing:
Fix Committed

Bug description:
[ Impact ]

5 GHz Wi-Fi networks are completely undetectable on Qualcomm WCN7850
(ath12k) starting with kernel 6.17, breaking wireless connectivity for
Snapdragon X Elite laptops.

Affected Hardware:
- Device: Lenovo Yoga Slim 7x (Snapdragon X Elite)
- Wi-Fi chipset: Qualcomm WCN7850 (ath12k_pci, hw2.0)
- Firmware: WLAN.HMT.1.1.c5-00302

Kernel Versions:
- Working: 6.16.0-21-qcom-x1e (5 GHz detected and functional)
- Broken: 6.17.x, 6.18.0-9-qcom-x1e (no 5 GHz BSS detected)
- Tested fix on: 6.19-rc5 (fully functional with patches)

Ubuntu Version:
Ubuntu 25.10

Symptoms:
- No 5 GHz networks appear in available network list
- `iw dev <interface> scan` shows only 2.4 GHz channels (1-13)
- 2.4 GHz networks work normally
- Regulatory domain correctly set (IN)
- No firmware loading errors
- Issue persists across multiple access points (ISP router on channel 36, Samsung hotspot)

[ Fix ]

Update ath12k/WCN7850/hw2.0/board-2.bin firmware.

[ Test Case ]

- 5 GHz Wi-Fi fully functional on current Questing kernel
- Both 2.4 GHz and 5 GHz networks detected and connectable
- Multiple access points tested successfully
- No firmware errors in dmesg

[ Where Problems Could Occur ]

Opaque firmware that - when loaded - can cause the usual kernel
problems (hang, freeze, stall, crash, ...)

[ Additional Information ]

Root Cause:
Broken frequency range filtering logic introduced between kernel 6.16 and 6.17. The regression involves changes to ath12k firmware statistics handling and regulatory domain synchronization that cause firmware protocol errors (-71, EPROTO) during 5 GHz scan preparation.

Investigation Details:
Initial suspicion was ASPM-related (commit e9cf6413e6a80), but symbol analysis confirmed this commit was not present in affected kernels. Subsequent analysis identified firmware statistics handling changes (commits bd6ec81 and 2977567) that altered state management and triggered the regression.

Fix:
A series of patches has been developed and tested on kernel 6.19-rc5:

Primary fix (critical):
- Patch 06: Remove broken frequency range filtering logic

Complete patch series attached:
- 9eb6d6bb9eb01e9767b8ad70bf503c1631d64c71 (Remove broken frequency range filtering) -- Primary fix
- 5946e4c0763755535f7f9f89761828b68a8019d1 (Improvements & cleanup)
- 26a6a6263f6c8919ade47f18814335e52384d474 (Improvements & cleanup)
- dae0671ab05a3a30cbba5e8b1f41e45a80c3900f (Improvements & cleanup)
- 9126482be6353f03a2844f60be1a569bc14a6738 (Improvements & cleanup)

Testing Results:
- 5 GHz Wi-Fi fully functional on kernel 6.19-rc5 with patch series applied
- Both 2.4 GHz and 5 GHz networks detected and connectable
- Multiple access points tested successfully
- No firmware errors in dmesg

Complete Technical Analysis:
Full investigation details, logs, and patch series available at:
https://bugs.launchpad.net/ubuntu-concept/+bug/2138308

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