MediaTek MT7902 Bluetooth DKMS Driver & Power Fix (0489:e156)

Production-ready out-of-tree DKMS kernel driver, power management fix, and diagnostic suite for the MediaTek MT7902 (Filogic 310) Bluetooth controller (Foxconn 0489:e156). Verified on Arch Linux and Omarchy Linux (Kernels 6.x / 7.x).

Authors: simonez & Arci
Version: 1.0.2
License: GNU GPL-2.0

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1. Hardware Architecture & Problem Resolution

The Hardware Context

Modern motherboards and laptops bundle Wi-Fi and Bluetooth onto a single M.2 Key-E card (such as the MediaTek MT7902 combo):

• Wi-Fi 6E: Routed via PCIe (14c3:7902) and supported in-tree via mt7921e.
• Bluetooth 5.3: Routed through the internal USB 2.0 bus with Foxconn OEM ID 0489:e156.

Why Stock Kernels Fail

1. Missing Upstream ID: While AzureWave variants (13d3:3579) are merged upstream in Linux v7.1+, the Foxconn device ID 0489:e156 is missing from in-tree drivers/bluetooth/btusb.c.
2. Generic Binding Limitations: Binding via new_id assigns driver_info = 0. Without the BTUSB_MEDIATEK vendor quirk, the controller fails MCU RAM firmware initialization (BT_RAM_CODE_MT7902_*.bin) and times out with error -110.
3. USB Autosuspend Audio Dropout: Under default aggressive USB autosuspend (power/control = auto), waking the controller interrupts high-bitrate audio streaming (Sony LDAC 990 kbps / 48 kHz), causing stuttering and disconnects.

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2. Key Components & Driver Features

• Patched btusb Driver: Registers USB_DEVICE(0x0489, 0xe156) with BTUSB_MEDIATEK | BTUSB_WIDEBAND_SPEECH | BTUSB_VALID_LE_STATES.
• Automated DKMS Integration: Automatically rebuilds the module on every kernel update (pacman -Syu) into /lib/modules/$(uname -r)/updates/dkms/.
• Permanent Power Stabilization: Deploys udev and modprobe rules to permanently maintain power/control = on (enable_autosuspend=0).
• Hardware Diagnostic Suite (bt-debug): Real-time CLI tool for hardware inspection, DKMS validation, and live audio stream monitoring.

Upstream Kernel Patch Diff

--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -645,6 +645,8 @@ static const struct usb_device_id quirks_table[] = {
 						     BTUSB_WIDEBAND_SPEECH },
 	{ USB_DEVICE(0x0489, 0xe158), .driver_info = BTUSB_MEDIATEK |
 						     BTUSB_WIDEBAND_SPEECH },
+	{ USB_DEVICE(0x0489, 0xe156), .driver_info = BTUSB_MEDIATEK |
+						     BTUSB_WIDEBAND_SPEECH },

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3. Installation & Removal

Automated Installation

git clone https://github.com/simonezpx3/btusb-mt7902-dkms.git
cd btusb-mt7902-dkms
chmod +x install.sh
sudo ./install.sh

The script automatically verifies prerequisites (dkms, linux-headers), builds and registers the module, deploys power stabilization rules (/etc/udev/rules.d/99-bluetooth-mt7902-power.rules, /etc/modprobe.d/btusb.conf), and installs bt-debug.

Removal

cd btusb-mt7902-dkms
sudo ./uninstall.sh

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4. Verification & Diagnostics (bt-debug)

Run the bundled diagnostic utility to verify hardware status, DKMS module binding, and active audio codec:

bt-debug            # Hardware overview, DKMS state, and connected devices
bt-debug --monitor  # Live audio packet stream telemetry

Example Diagnostic Output

===================================================================
    MediaTek MT7902 Bluetooth (Foxconn 0489:e156) Diagnostic     
===================================================================
[1] HARDWARE & USB BUS:    ● 0x0489:0xe156 (Power: on, Autosuspend: DISABLED)
[2] DRIVER & DKMS:         ● Installed (v1.0) via /lib/modules/updates/dkms/
[3] CONTROLLER & DEVICES:  ● Powered ON | AN01 Connected [Battery: 100%]
[4] AUDIO & PIPEWIRE:      ● Sink: AN01 | Codec: LDAC (float32le 2ch 48000Hz)
===================================================================