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

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: [email protected]
          Reporter: [email protected]
        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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Bastien Nocera ([email protected]) changed:

What |Removed |Added
----------------------------------------------------------------------------

             Status|NEW                         |RESOLVED
                 CC|                            |[email protected]
         Resolution|---                         |DUPLICATE

--- Comment #1 from Bastien Nocera ([email protected]) ---

*** This bug has been marked as a duplicate of bug 220682 ***

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Alex ([email protected]) changed:

What |Removed |Added
----------------------------------------------------------------------------

             Status|RESOLVED                    |REOPENED
         Resolution|DUPLICATE                   |---

--- Comment #2 from Alex ([email protected]) ---
I respectfully request this bug be reopened as it represents a different issue than bug #220682.

## Key Difference

**Bug #220682 (USB ID 0489:e111):**
- Bluetooth worked initially after boot
- Stopped working after GNOME login (timing-sensitive)
- Fixed by libmtp/libgphoto2 blacklist updates

**This bug #220986 (USB ID 13d3:3596):**
- Bluetooth NEVER initializes, even at boot
- Fails before GNOME login occurs
- NOT fixed by libmtp/libgphoto2 updates

## Testing Completed (2026-01-21)

I have installed the corrected package updates:
- libmtp-1.1.22-2.fc43.x86_64 (includes 13d3:3596 blacklist)
- libgphoto2-2.5.33-1.fc43.x86_64 (includes 13d3:3596 blacklist)

Performed full cold boot procedure:
1. Complete shutdown (not reboot)
2. Unplugged power for 30+ seconds
3. Booted directly to Linux (no Windows boot first)

## Current Status

Bluetooth still fails with identical error:

```
[   19.247336] Bluetooth: hci0: Opcode 0x0c03 failed: -110
```

System details:
- USB device detected: Bus 001 Device 003: ID 13d3:3596 IMC Networks Wireless_Device
- btusb driver binds correctly to interfaces 0 and 1
- hci0 device created in /sys/class/bluetooth/
- Firmware exists: /lib/firmware/mediatek/mt7925/BT_RAM_CODE_MT7925_1_1_hdr.bin
- HCI_Reset command times out (error -110 = ETIMEDOUT)
- Chip does not respond to any HCI commands
- No firmware loading attempted (fails before that stage)

## Root Cause Analysis

The libmtp/libgphoto2 fix resolved the USB ID conflict, but a **second, independent issue remains**: the btusb driver cannot communicate with the MT7925 chip at the hardware level. The chip does not respond to HCI_Reset or any other HCI commands.

This is a kernel driver initialization bug, not a userspace library conflict.

## Evidence This Is Different

1. **Timing:** Bug #220682 worked until login; this bug fails immediately at boot
2. **No gvfs interaction:** Bluetooth fails before any GNOME services start
3. **Package updates don't help:** libmtp/libgphoto2 blacklists are installed but issue persists
4. **Cold boot doesn't help:** Full power cycle completed, issue remains
5. **Hardware works:** Device functions correctly in Windows 11

## Request

Please reopen this bug as a separate kernel driver issue. The USB ID conflict fix (bug #220682) is necessary but not sufficient to resolve this bug.

System: Fedora 43, Kernel 6.18.5-200.fc43.x86_64
Hardware: MediaTek MT7925 (USB ID 13d3:3596, AzureWave 6040 subsystem)

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--- Comment #3 from Alex ([email protected]) ---
additional context:

## What I've Tested (2026-01-21)

**1. Applied the USB ID blacklist fixes:**
- Installed libmtp-1.1.22-2.fc43.x86_64 (includes 13d3:3596 blacklist)
- Installed libgphoto2-2.5.33-1.fc43.x86_64 (includes 13d3:3596 blacklist)

**2. Performed full cold boot:**
- Shut down completely (not reboot)
- Unplugged power cable for 30+ seconds to clear hardware state
- Booted directly to Linux (did not boot Windows first)

**3. Verified Windows functionality:**
- Rebooted to Windows 11
- Bluetooth works perfectly (can pair devices, transfer files, etc.)
- This confirms the hardware itself is not defective

**4. Returned to Linux:**
- Bluetooth still fails with the same error

## Current Behavior in Linux

Bluetooth fails immediately at boot, before any desktop environment loads:

```
[   19.247336] Bluetooth: hci0: Opcode 0x0c03 failed: -110
```

Technical details:
- USB device is detected: Bus 001 Device 003: ID 13d3:3596 IMC Networks Wireless_Device
- btusb driver binds to the device correctly
- hci0 device is created in /sys/class/bluetooth/
- Firmware file exists:
/lib/firmware/mediatek/mt7925/BT_RAM_CODE_MT7925_1_1_hdr.bin
- **Problem:** HCI_Reset command times out (error -110 = ETIMEDOUT)
- The chip does not respond to any HCI commands from the Linux driver
- Firmware loading is never attempted because the driver fails before that stage

## Why This Is Different From Bug #220682

**Bug #220682 (USB ID 0489:e111):**
- Bluetooth worked after boot
- Failed only after user logged into GNOME desktop
- Caused by libmtp/libgphoto2 probing the device during desktop startup
- **Fixed** by blacklisting the USB ID in libmtp/libgphoto2

**This bug #220986 (USB ID 13d3:3596):**
- Bluetooth never works, not even for a moment
- Fails at boot time, before any desktop environment starts
- Fails even with libmtp/libgphoto2 blacklists applied
- **Not fixed** by the package updates

## Root Cause

There are TWO separate issues affecting USB ID 13d3:3596:

1. **USB ID conflict** (shared with bug #220682) - RESOLVED by package updates
2. **Kernel driver initialization failure** (unique to this bug) - UNRESOLVED

The btusb driver cannot communicate with the MT7925 chip at the hardware level. Since the same hardware works perfectly in Windows, this indicates the Linux driver is missing vendor-specific initialization code or using an incorrect initialization sequence for this particular chip variant.

## Why Hardware Defect Is Ruled Out

- Device works perfectly in Windows 11 (Bluetooth pairs, connects, transfers data)
- WiFi portion of the same combo card works in Linux (mt7925 driver)
- USB device is detected and enumerated correctly in Linux
- This is a software/driver issue, not hardware

## Request

Please reopen this bug as a kernel driver issue. The libmtp/libgphoto2 fixes from bug #220682 are necessary but not sufficient to make this device work.

**System Information:**
- OS: Fedora Linux 43 (Workstation Edition)
- Kernel: 6.18.5-200.fc43.x86_64
- Hardware: MediaTek MT7925 Bluetooth/WiFi combo (Filogic 310)
- USB ID: 13d3:3596 (IMC Networks)
- Subsystem: AzureWave 6040
- Motherboard: ASUS TUF GAMING B650M-E WIFI

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Alex ([email protected]) changed:

What |Removed |Added
----------------------------------------------------------------------------

     Kernel Version|                            |6.18.5-200.fc43.x86_64

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Alex ([email protected]) changed:

What |Removed |Added
----------------------------------------------------------------------------

            Summary|MediaTek MT7925 Bluetooth   |MediaTek MT7902 Bluetooth
                   |adapter (USB 13d3:3596)     |adapter (USB 13d3:3596) -
                   |fails to initialize -       |missing kernel support for
                   |reports as unsupported      |hardware variant 0x7902
                   |hardware variant 0x7902     |

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--- Comment #4 from Alex ([email protected]) --- UPDATE 2026-01-21: Root cause identified, kernel fix still needed

CORRECTION: This chip is MT7902, not MT7925.
Evidence:
- PCIe ID: 14c3:7902 ("MT7902 802.11ax PCIe Wireless Network Adapter")
- Hardware variant reports: 0x7902
- Firmware build: 20220107141051

KERNEL CHANGES REQUIRED:

1. drivers/bluetooth/btusb.c - Add USB ID:
{ USB_DEVICE(0x13d3, 0x3596), .driver_info = BTUSB_MEDIATEK |
BTUSB_WIDEBAND_SPEECH }

2. drivers/bluetooth/btmtk.c - Add hardware variant 0x7902 to switch statement:
case 0x7902:
(alongside existing 0x7922, 0x7925, 0x7961)

3. linux-firmware - Include MT7902 Bluetooth firmware (BT_RAM_CODE_MT7902_1_1_hdr.bin)

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