Bluetooth Audio Stuttering During WiFi Activity on RTL8852CE

Bluetooth Audio Stuttering During WiFi Activity on RTL8852CE

UPDATE: I’ve found that kernel 6.11.4 works perfectly while 6.12.9 has the audio stuttering issue. Detailed analysis and findings in this comment.

System Information

  • OS: Fedora Linux 41 (Workstation Edition)
  • Kernel: 6.12.8-200.fc41.x86_64
  • Hardware:
    • Lenovo IdeaPad Slim 5 14AHP9 (Model: 83DB)
    • BIOS: LENOVO NGCN26WW (05/27/2024)
  • CPU: AMD Ryzen 7 8845HS w/ Radeon 780M Graphics
  • Memory: 28 GiB (12.2% used)
  • Audio Stack:
    • PipeWire v1.2.7 (active)
    • ALSA v: k6.12.8-200.fc41.x86_64

Network Hardware

  • WiFi/BT Controller: Realtek RTL8852CE PCIe 802.11ax
    • Driver: rtw89_8852ce (kernel version)
    • Bus ID: 02:00.0
  • Bluetooth:
    • Realtek Bluetooth Radio
    • Driver: btusb v0.8
    • Bus ID: 1-5:3
    • Bluetooth version: 5.3
    • LMP version: 12

Audio Device

  • Device: AirPods Pro (AA:55:24:08:F8:F2)
    • Audio Profiles: A2DP (Sink), HFP
    • Class: 0x00240418
    • Supported UUIDs: Audio Sink, A/V Remote Control, Handsfree

Connection Details

  • WiFi: 5GHz band (5500 MHz), VHT-MCS 9 80MHz, Signal -55 dBm
  • Operating Environment: GNOME 47.2 on Wayland

Issue Description

When using Bluetooth audio while WiFi is active:

  • Audio stutters during network activity (both upload and download)
  • Problem occurs with both AAC and SBC codecs
  • Stuttering is intermittent, typically after initial 1-2 seconds of network activity
  • Issue disappears when WiFi is disabled
  • WiFi events show RSSI drops to -110 dBm during stutters
  • Problem affects AirPods Pro (AAC codec) and has been observed with other Bluetooth audio devices (SBC codec)

To Reproduce

  1. Connect Bluetooth audio device
  2. Start audio playback (e.g., Spotify, YouTube)
  3. Initiate network activity (e.g., start a download or speed test)
  4. Audio will stutter/skip during network activity

Diagnostic Logs

During stuttering events:

> journalctl -f
Jan 12 15:52:46 fedora wpa_supplicant[1270]: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-56 noise=9999 txrate=468000

> sudo iw event
wlp2s0 (phy #4): CQM event: RSSI (-110 dBm) went above threshold

Debug Information

journalctl during module reload shows:

kernel: rtw89_8852ce 0000:02:00.0: [RX_DCK] S1 RXDCK timeout

Attempted Solutions

  1. Modified Bluetooth connection parameters:
MinConnectionInterval=7
MaxConnectionInterval=9
SlaveLatency=0
ConnectionSupervisionTimeout=400
  1. Modified WiFi/Bluetooth coexistence settings:
options rtw89_pci disable_ps_mode=1
options rtw89_core coex_bt_rssi_th=70
  1. Disabled power saving features

None of these solutions fully resolved the issue.


Additional Notes

  • No stuttering occurs when using ethernet with WiFi disabled
  • Issue persists across different Bluetooth codecs
  • Both WiFi and Bluetooth are part of the same RTL8852CE chip
  • Device presents Bluetooth through internal USB interface despite being integrated
  • GTK uses TKIP while PTK uses CCMP, possibly indicating a suboptimal router configuration

Environment Details

$ lspci -nnk | grep -A3 Network
02:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8852CE PCIe 802.11ax Wireless Network Controller [10ec:c852] (rev 01)
        Subsystem: Lenovo Device [17aa:5852]
        Kernel driver in use: rtw89_8852ce
        Kernel modules: rtw89_8852ce

Questions

  1. Are there known issues with RTL8852CE WiFi/Bluetooth coexistence?
  2. Are there firmware updates available that might address this?
  3. Could this be related to the RX_DCK timeout issues observed in the logs?
  4. Are there additional debugging steps or logs that would be helpful?

Please let me know if you need any additional information or would like me to run specific tests.

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Regarding number 2, have a look at fwupdmgr. If there are firmware updates for any of the detected kit, it should inform you, download them and install them.

Thanks for the suggestion! I ran fwupdmgr, but no firmware updates were available for my devices—everything is up-to-date.

I’ve got the same issues too a tee with a B650I AX mobo (which uses the same RTL8852CE controller) using the KDE 41 edition. For me, it’s occurred when booting into a live manjaro environment too but not for mint. Regarding Q3, I didn’t get anything out of the ordinary when running journalctl --follow.
let me know if you find the issue

Also few days ago there was this post:

with two other people who are having simlar issues with the same controller. Too me it sounds like its a common issue with the drivers for this hardware

UPDATE: Kernel Version Correlation Found

After further testing, I’ve identified a clear correlation between kernel versions and the Bluetooth audio stuttering:

  • Kernel 6.11.4-301.fc41.x86_64: :white_check_mark: Works perfectly, no audio stuttering
  • Kernel 6.12.9-200.fc41.x86_64: :x: Audio stutters during WiFi activity

Reproduction Steps:

  1. Fresh Fedora installation (comes with 6.11.4) - Bluetooth audio works perfectly
  2. After sudo dnf update and reboot (updates to 6.12.9) - Bluetooth audio starts stuttering

Key Differences Found Between Kernels (via diff analysis):

  1. WiFi Firmware Changes:

    • 6.11.4: Uses rtw8852c_fw.bin (version 0.27.56.14)
    • 6.12.9: Uses rtw8852c_fw-1.bin (version 0.27.97.0)
  2. Bluetooth Module Changes:

    • Different srcversion identifiers:
      • 6.11.4: B845E3D337E984D458032D7
      • 6.12.9: 8DD395661BE4304F8520852
  3. Additional Firmware Elements in 6.12.9 (not present in 6.11.4):

    • BB version: 00 28 00 00
    • Radio A version: 00 63 00 00
    • NCTL version: 00 11 00 00
    • TXPWR version: 00 69 01 00
    • PWR_TRK version: 00 26 00 00

Both kernels use the same Bluetooth firmware (rtl8852cu_fw_v2.bin), but the module build and handling appear to be different. The additional firmware elements and power tracking in 6.12.9 might be related to the interference issues.

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