RE: [REGRESSION] rtw89_8852ae: HT/VHT/HE not negotiated, stuck at 54 Mbps since kernel 6.18

[Ping-Ke Shih <pkshih@realtek.com>]

Chris Wituchowski <flashrift@gmail.com> wrote:
> *resend as plaintext - sent originally as html, sorry!*
> 
> Hi,
> 
> I'm reporting a regression in the rtw89_8852ae driver. After upgrading from
> kernel 6.14.x (Fedora 42 GA) to 6.18.x (Fedora 43), my RTL8852AE WiFi adapter
> no longer negotiates HT, VHT, or HE with the access point. The connection falls
> back to legacy 802.11a at 54 Mbps on 5 GHz, delivering only ~20 Mbps real-world
> throughput on a gigabit link.
> 
> == Hardware ==
> 
>   Adapter: Realtek RTL8852AE 802.11ax PCIe (WiFi 6, 2x2 MIMO)
>   PCI ID:  10ec:8852 (subsystem: 17aa:4852, Lenovo)
>   System:  Lenovo laptop
> 
> == Software ==
> 
>   Broken:   6.18.13-200.fc43.x86_64 (also 6.18.10, 6.18.12 — all broken)
>   Last OK:  6.14.x (Fedora 42 GA kernel — WiFi worked at full 802.11ax speeds)
>   Driver:   rtw89_8852ae (in-tree)
>   Firmware: rtw8852a_fw.bin (v0.13.36.2 / 52acc807)
>   Distro:   Fedora 43
> 
> == Symptoms ==
> 
> The adapter connects to a 5 GHz AP (channel 157) but fails to negotiate
> HT/VHT/HE, falling back to legacy 20 MHz / 54 Mbps:
> 
>   $ iw dev wlp3s0 link
>   Connected to 52:bb:9f:a2:d8:4a (on wlp3s0)
>       SSID: Innernette
>       freq: 5785.0
>       signal: -29 dBm
>       rx bitrate: 54.0 MBit/s
>       tx bitrate: 54.0 MBit/s
> 
>   $ iw dev wlp3s0 info
>       channel 157 (5785 MHz), width: 20 MHz (no HT), center1: 5785 MHz
> 
> Debugfs confirms the driver is not reporting any HT/VHT/HE capabilities
> for the station:
> 
>   /sys/kernel/debug/ieee80211/phy*/netdev:wlp3s0/stations/<bssid>/ht:
>       "ht not supported"
> 
>   /sys/kernel/debug/ieee80211/phy*/netdev:wlp3s0/stations/<bssid>/vht:
>       "VHT not supported"
> 
>   /sys/kernel/debug/ieee80211/phy*/netdev:wlp3s0/stations/<bssid>/he:
>       "HE not supported"
> 
> == AP Capabilities (confirmed via iw scan) ==
> 
> The AP fully supports HT, VHT, and HE:
> 
>   - HT: HT20/HT40, MCS 0-15 (2 spatial streams)
>   - VHT: up to 80 MHz, MCS 0-9 for 2 SS
>   - HE (WiFi 6): full 802.11ax support
>   - Max advertised rate: 1170 Mbps
> 
> The AP's "HT protection" field shows "non-HT mixed mode", confirming it
> sees the client as a non-HT legacy station.
> 
> == What I've Ruled Out ==
> 
>   1. Signal strength: Excellent (-27 to -48 dBm across tests)
>   2. WPA3 vs WPA2: Same result with both (key-mgmt sae and psk)
>   3. wpa_supplicant vs iwd: Same result with both backends
>   4. Firmware: Already on latest version (v0.13.36.2)
>   5. Driver reload: Full unload/reload of rtw89 module stack — no change
>   6. Power save: Disabled (disable_ps_mode module parameter)
>   7. wl module conflict: Blacklisted via /etc/modprobe.d/blacklist-wl.conf
>   8. Regulatory: US domain active, DFS-FCC, correct for channel 157
>   9. Regression within 6.18.x: Changelogs for 6.18.10→6.18.13 contain
>      ZERO rtw89/mac80211/cfg80211 changes. Bug exists across all 6.18.x.
> 
> == Likely Cause ==
> 
> Between kernel 6.14 and 6.18, the rtw89 driver received hundreds of commits
> for WiFi 7 MLO (Multi-Link Operation) support, including:
> 
>   - mac80211 per-link STA refactoring (HT/VHT/HE caps moved to per-link
>     link_sta structures)

That should be compatible with WiFi 6 and earlier. 

>   - 54+ chanctx commits in rtw89 ("chan: manage active interfaces",
>     "tweak setting of channel and TX power for MLO", etc.)

This driver is to support WiFi 6/7 chips. The WiFi 6 chips should work
as before these patches. 

>   - "disable EHT protocol by chip capabilities"

EHT is used WiFi 7 chips, so no worries about this.

> 
> The RTL8852AE is a gen1 WiFi 6 chip. The MLO work was developed and tested
> primarily on gen2 WiFi 7 chips (RTL8922A/E). It appears the gen1 code path
> through the new per-link framework is not correctly populating HT/VHT/HE
> capabilities during association.
> 
> == Steps to Reproduce ==
> 
>   1. System with RTL8852AE (10ec:8852) running kernel 6.18.x

I tried two kernel 6.18.1 and 6.19.3 with same firmware 0.13.36.2 (52acc807)
that both work with HE rates.

I did connection by 'iw connect' command instead, because my AP is non-secure. 

>   2. Connect to any 5 GHz 802.11ax access point
>   3. Observe: iw dev <if> info shows "width: 20 MHz (no HT)"

This is the output in my side:

        channel 36 (5180 MHz), width: 80 MHz, center1: 5210 MHz

>   4. Observe: iw dev <if> link shows 54.0 MBit/s bitrate

This is the output in my office (the rate isn't good, but still HE rate)

        rx bitrate: 600.4 MBit/s 80MHz HE-MCS 11 HE-NSS 1 HE-GI 0 HE-DCM 0
        tx bitrate: 183.7 MBit/s 80MHz HE-MCS 2 HE-NSS 2 HE-GI 2 HE-DCM 0

>   5. Observe: debugfs ht/vht/he files all report "not supported"

This is the output in stations/<bssid>/ directory:

$ sudo cat *capa | grep supported
EHT not supported
HE supported
ht supported
VHT supported

> 
> == Expected Result ==
> 
> Connection should negotiate HT/VHT/HE (80 MHz, WiFi 6) as it did on
> kernel 6.14.x, providing 800+ Mbps link rates.
> 

I don't have a Fedora on hand, and I tested above by Ubuntu + updated pre-built
kernel [1]. Please try if Ubuntu with 6.18.1 or 6.19.3 kernel can work in your side.

[1] https://kernel.ubuntu.com/mainline/v6.19.3/