[Bug 220986] New: MediaTek MT7925 Bluetooth adapter (USB 13d3:3596) fails to initialize - reports as unsupported hardware variant 0x7902

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=220986

            Bug ID: 220986
           Summary: MediaTek MT7925 Bluetooth adapter (USB 13d3:3596)
                    fails to initialize - reports as unsupported hardware
                    variant 0x7902
           Product: Drivers
           Version: 2.5
          Hardware: Other
                OS: Linux
            Status: NEW
          Severity: blocking
          Priority: P3
         Component: Bluetooth
          Assignee: linux-bluetooth@vger.kernel.org
          Reporter: aamolodc@gmail.com
        Regression: No

The MediaTek MT7925 WiFi/Bluetooth combo card with USB ID 13d3:3596 fails to
initialize Bluetooth functionality. The chip reports hardware variant 0x7902
instead of the expected 0x7925, causing the btmtk driver to request
non-existent firmware (mt7902/BT_RAM_CODE_MT7902_1_1_hdr.bin).

When attempting to use MT7925 firmware via symlink, the chip fails with
HCI_Reset timeout (Opcode 0x0c03 failed: -110).

WiFi functionality works (slowly) via the mt7925 driver, but Bluetooth is
completely non-functional.

STEPS TO REPRODUCE:
1. Boot Linux with MediaTek MT7925 (USB 13d3:3596) present
2. Observe Bluetooth fails to initialize
3. Check dmesg for firmware load failure or HCI timeout

ACTUAL RESULT:
- Without firmware symlink: "Direct firmware load for
mediatek/mt7902/BT_RAM_CODE_MT7902_1_1_hdr.bin failed with error -2"
- With MT7925 firmware symlinked as MT7902: "Opcode 0x0c03 failed: -110"
(HCI_Reset timeout)
- No Bluetooth controller available

EXPECTED RESULT:
Bluetooth adapter should initialize and be usable

SYSTEM INFORMATION:

Kernel: 6.18.5-200.fc43.x86_64
Distro: Fedora 43 (Workstation Edition)

USB Device:
  Bus 001 Device 003: ID 13d3:3596 IMC Networks Wireless_Device
  Manufacturer: MediaTek Inc.
  Product: Wireless_Device

Loaded modules:
  btusb, btmtk, bluetooth

DMESG OUTPUT:

[    5.657894] usbcore: registered new interface driver btusb
[    5.669557] bluetooth hci0: Direct firmware load for
mediatek/mt7902/BT_RAM_CODE_MT7902_1_1_hdr.bin failed with error -2
[    5.669561] Bluetooth: hci0: Failed to load firmware file (-2)
[    5.669563] Bluetooth: hci0: Failed to set up firmware (-2)
[    5.669565] Bluetooth: hci0: HCI Enhanced Setup Synchronous Connection
command is advertised, but not supported.

After symlinking MT7925 firmware as MT7902 and reloading btusb:
[  304.624964] Bluetooth: hci0: Opcode 0x0c03 failed: -110

ANALYSIS:
The btmtk driver reads hardware variant 0x7902 from the chip and constructs
firmware path accordingly. However:
1. No MT7902 Bluetooth firmware exists in linux-firmware
2. MT7925 firmware is not compatible with the 0x7902 variant (causes HCI
timeout)
3. The 0x7902 variant may need specific firmware or driver modifications

ADDITIONAL NOTES:
- This device works correctly on Windows
- WiFi portion of the combo card works (via mt7925 WiFi driver)
- Multiple users report similar issues with MT7925 variants on various laptops
- Related: Launchpad bug #2078878

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