Add Bluetooth support for the MediaTek MT7927 (Filogic 380), a PCIe
combo WiFi 7 + BT 5.4 module. The BT subsystem uses hardware variant
0x6639 and connects via USB.

The MT7927 is shipping in motherboards and PCIe add-in cards from ASUS,
Gigabyte, Lenovo, MSI, and TP-Link since mid-2024. Without these patches,
users see "Unsupported hardware variant (00006639)" or the BT subsystem
hangs during firmware download.

The series consists of eight patches:

  [1/8] Bluetooth: btmtk: Add MT6639 (MT7927) Bluetooth support
  [2/8] Bluetooth: btmtk: fix ISO interface setup for single alt setting
  [3/8] Bluetooth: btusb: Add MT7927 ID for ASUS ROG Crosshair X870E Hero
  [4/8] Bluetooth: btusb: Add MT7927 ID for Lenovo Legion Pro 7 16ARX9
  [5/8] Bluetooth: btusb: Add MT7927 ID for Gigabyte Z790 AORUS MASTER X
  [6/8] Bluetooth: btusb: Add MT7927 ID for MSI X870E Ace Max
  [7/8] Bluetooth: btusb: Add MT7927 ID for TP-Link Archer TBE550E
  [8/8] Bluetooth: btusb: Add MT7927 ID for ASUS X870E / ProArt X870E-Creator

Three driver changes are needed for MT6639 (patch 1):

1. CHIPID workaround: On some boards the BT USB MMIO register reads
   0x0000 for dev_id. Force dev_id to 0x6639 only when the USB VID/PID
   matches a known MT6639 device, avoiding misdetection if a future
   chip also reads zero. This follows the WiFi-side pattern.

2. Firmware naming: MT6639 uses firmware version prefix "2_1" instead of
   "1_1" used by MT7925 and other variants. The firmware path is
   mediatek/mt7927/BT_RAM_CODE_MT6639_2_1_hdr.bin, using the mt7927
   directory to match the WiFi firmware convention. The filename will
   likely change to use MT7927 once MediaTek submits a dedicated
   Linux firmware binary.

3. Section filtering: The firmware binary contains 9 sections, but only
   sections with (dlmodecrctype & 0xff) == 0x01 are Bluetooth-related.
   Sending WiFi/other sections causes an irreversible BT subsystem hang.

Patch 2 fixes the ISO interface setup for devices that expose only a
single alternate setting (alt 0) on the ISO endpoint. Without this fix,
btmtk_usb_claim_iso_intf() fails with EINVAL, causing ~20 second
initialization delays on 13d3:3588 devices.

WBS (Wideband Speech) was verified on MT7927 hardware. The controller
reports LMP_TRANSPARENT, LMP_ERR_DATA_REPORTING, and mSBC codec support.
A btmon capture confirms eSCO links establish with Transparent air mode
(mSBC) and 60-byte frames. BTUSB_WIDEBAND_SPEECH is correct for this
controller family.

Tested on:
- ASUS ROG Crosshair X870E Hero (USB 0489:e13a)
- ASUS ROG STRIX X870E-E (USB 13d3:3588)
- ASUS ROG STRIX B850-E GAMING WIFI (USB 0489:e13a)
- Gigabyte Z790 AORUS MASTER X (USB 0489:e10f)
- Lenovo Legion Pro 7 16ARX9 (USB 0489:e0fa)

Changes in v5:
- Fix patch 8/8 commit message: the ~19 second delay note was misleading
  since patch 2/8 already fixes that issue. Updated to clarify the
  relationship between the two patches (suggested by Luiz Augusto von
  Dentz)

Link to v4: https://lore.kernel.org/linux-bluetooth/20260330-mt7927-bt-support-v4-0-cecc025e7062@jetm.me/ (local)

Signed-off-by: Javier Tia <redacted>
---
Javier Tia (8):
      Bluetooth: btmtk: Add MT6639 (MT7927) Bluetooth support
      Bluetooth: btmtk: fix ISO interface setup for single alt setting
      Bluetooth: btusb: Add MT7927 ID for ASUS ROG Crosshair X870E Hero
      Bluetooth: btusb: Add MT7927 ID for Lenovo Legion Pro 7 16ARX9
      Bluetooth: btusb: Add MT7927 ID for Gigabyte Z790 AORUS MASTER X
      Bluetooth: btusb: Add MT7927 ID for MSI X870E Ace Max
      Bluetooth: btusb: Add MT7927 ID for TP-Link Archer TBE550E
      Bluetooth: btusb: Add MT7927 ID for ASUS X870E / ProArt X870E-Creator

 drivers/bluetooth/btmtk.c     | 63 ++++++++++++++++++++++++++++++++++++++-----
 drivers/bluetooth/btmtk.h     |  7 +++--
 drivers/bluetooth/btmtksdio.c |  2 +-
 drivers/bluetooth/btusb.c     | 12 +++++++++
 4 files changed, 75 insertions(+), 9 deletions(-)
---
base-commit: 7f9446b23ac77f46d356b354ea8da49113e8000d
change-id: 20260305-mt7927-bt-support-6589a50c961f

Best regards,
--  
Javier Tia [off-list ref]