ath11k: QCN9074: low HE-MCS index

[Tanguy Serrat]

Hi everyone,

In my quest to get 2x QCN9074 paired and achieving high throughput
data transfers, I am now facing issues with the AP configuration.

Specifically, I cannot get more than HE-MCS 5 (AP and client 50cm
apart) although SNR and RSSI are always very strong and supposedly in
specs (SNR > 40db or RSSI < -48db).

iw wlp6s0 link
Connected to 00:15:61:27:cd:dc (on wlp6s0)
SSID: Space
freq: 5745
RX: 1073584482 bytes (708567 packets)
TX: 355824214 bytes (256143 packets)
signal: -40 dBm
rx bitrate: 1729.3 MBit/s 160MHz HE-MCS 4 HE-NSS 4 HE-GI 0 HE-DCM 0
tx bitrate: 1729.3 MBit/s 160MHz HE-MCS 4 HE-NSS 4 HE-GI 0 HE-DCM 0

In this case iperf3 shows ~950Mbits/s transfer speed. I am hoping to
get at least twice as much.

It seems to me that either mac80211, ath11k or hostapd are not
advertising the available capabilities correctly. I have tried setting
hostapd he_basic_mcs_set=65530 or others but did not help.

I have added ieee80211_regdom=FR option to cfg80211 module on the AP
side. Channel selection is done with ACS survey. I also tried other
channels/frequencies without success eg. 5500Mhz.

iw reg get
global
country FR: 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 - 71000 @ 2160), (N/A, 40), (N/A)

phy#0 (self-managed)
country US: DFS-FCC
(2402 - 2472 @ 40), (6, 30), (N/A)
(5170 - 5250 @ 80), (N/A, 30), (N/A), AUTO-BW
(5250 - 5330 @ 80), (N/A, 24), (0 ms), DFS, AUTO-BW
(5490 - 5730 @ 160), (N/A, 24), (0 ms), DFS, AUTO-BW
(5735 - 5895 @ 160), (N/A, 30), (N/A), AUTO-BW
(5945 - 7125 @ 160), (N/A, 27), (N/A), NO-OUTDOOR, AUTO-BW

Current setup is:
- Intel x86
- Ubuntu 22.04
- Kernel built from ath 6.4.0-rc6-wt-ath+ (commit:
c60d15f389ef9832a8da410e438d81b10327751f)
with commit reverted from the bug ticket I opened
(https://bugzilla.kernel.org/show_bug.cgi?id=217536).
- 1x QCN9074 as AP, 1x as managed client 50cm apart
- Both AP and Client are running with the latest 2.7.0 FW.

I have started from this ticket
(https://bugzilla.kernel.org/show_bug.cgi?id=217286) hostapd config
file, and adapted, please find attached.

Anyone seeing what could be my issue / how I could debug further ?

Thank you !
Tanguy
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