linux-kernel - 6 Ghz frequencies always listed as disabled in newer kernels with Mediatek MT7921K (RZ608)

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Message-ID: <18be5ba2-6dc4-4766-9944-59cb46c8dfaf@devture.com>
Date: Mon, 10 Feb 2025 16:56:17 +0200
From: Slavi Pantaleev <slavi@...ture.com>
To: Felix Fietkau <nbd@....name>, Lorenzo Bianconi <lorenzo@...nel.org>,
 Ryder Lee <ryder.lee@...iatek.com>, Kalle Valo <kvalo@...nel.org>,
 Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Ming Yen Hsieh <mingyen.hsieh@...iatek.com>, Deren Wu
 <deren.wu@...iatek.com>, linux-wireless@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org
Subject: 6 Ghz frequencies always listed as disabled in newer kernels with
 Mediatek MT7921K (RZ608)

Hello!

This is in regard to Bugzilla Bug 218731 - Tri-band AMD RZ608 (MediaTek 
MT7921K) has 6GHz band disabled in kernel 6.7+ despite working in <=6.6

URL: https://bugzilla.kernel.org/show_bug.cgi?id=218731

I'm in Bulgaria and `iw reg get` reports this:

```
global
country BG: DFS-ETSI
         (2400 - 2483 @ 40), (N/A, 20), (N/A)
         (5150 - 5250 @ 80), (N/A, 23), (N/A), NO-OUTDOOR, AUTO-BW
         (5250 - 5350 @ 80), (N/A, 20), (0 ms), NO-OUTDOOR, DFS, AUTO-BW
         (5470 - 5725 @ 160), (N/A, 26), (0 ms), DFS
         (5725 - 5875 @ 80), (N/A, 13), (N/A)
         (5945 - 6425 @ 160), (N/A, 23), (N/A), NO-OUTDOOR
         (57000 - 66000 @ 2160), (N/A, 40), (N/A)
```

For testing purposes, I've also tried switching to another regulatory 
domain (`US`, `DE`, `SE`, `NL`) via `iw reg set ..`.

Regardless of the regulatory domain, `iw list | grep -A 15 Frequencies` 
always reports the 6 Ghz frequencies as disabled on newer kernels.

As the original bug reporter has discovered, the regression begins to 
appear in kernel 6.7.0 while it isn't present in 6.6.30.
I've done a bisection and the results are like this:

1. [bad] mainline (954a209f431c06b62718a49b403bd4c549f0d6fb)
2. [good] v6.6.30
3. [bad] v6.7.12
4. [good] v6.6
5. [bad] edd8e84ae9514e93368f56c3715b11af52df6c3b
6. [bad] 89ed67ef126c4160349c1b96fdb775ea6170ac90
7. [good] b827ac419721a106ae2fccaa40576b0594edad92
8. [bad] d1a02ed66fe62aa2edd77bd54e270ebc33bd12ff
9. [good] 3abbd0699b678fc48e0100704338cff9180fe4bb
10. [good] 5a423552e0d9bb882f22cb0bf85f520ca2692706
11. [bad] 56a7bb12c78ffa1b02e154b1d779ed2a1555fa3c
12. [good] a3c2dd96487f1dd734c9443a3472c8dafa689813
13. [bad] 089482a06b74a40d45773b1871182e8f04be026b
14. [good] fce9c967820a72f600abbf061d7077861685a14d
15. [good] c948b5da6bbec742b433138e3e3f9537a85af2e5
16. [good] 9585316a2aaf773a67846bdc8bbdd4df1e9622fa
17. [good] 51ba0e3a15eb1643116a93674e230e11b9499592
18. [bad] 09382d8f8641bc12fffc41a93eb9b37be0e653c0
19. [good] 4fc8df50fd41c2762d893211487be0ecb24c6a05

09382d8f8641bc12fffc41a93eb9b37be0e653c0 is reported as the first bad 
commit.

URL: 
https://kernel.googlesource.com/pub/scm/linux/kernel/git/stable/linux/+/09382d8f8641bc12fffc41a93eb9b37be0e653c0

Regards