Hi stable@vger.kernel.org,

Could you please apply:

1. Commit a7208610761ae ("Bluetooth: btmtk: Remove resetting mt7921 before downloading the fw") to v6.12.x (it's already in v6.14).

2. Commit 33634e2ab7c6 ("Bluetooth: btmtk: Remove the resetting step before downloading the fw") to v6.12.x and v6.14.x.

These fixes address an issue with some audio interfaces failing to initialise during boot on kernels 6.11+. As noted in my original analysis below, the MediaTek Bluetooth controller reset increases the device setup time from ~200ms to ~20s and can interfere with other USB devices on the bus.

Thanks, Geoffrey.

On Fri, Mar 28, 2025 at 08:44:49AM +1030, Geoffrey D. Bennett wrote:

Hi all,

Sorry, I see that an identical patch has already been applied to bluetooth-next https://lore.kernel.org/linux-bluetooth/20250315022730.11071-1-hao.qin@media...

While I'm glad the issue is being addressed, my original patch https://lore.kernel.org/linux-bluetooth/Z8ybV04CVUfVAykH@m.b4.vu/ contained useful context and tags that didn't make it into the final commit.

For getting this fix into current kernel releases 6.12/6.13/6.14, I think the patch needs the "Cc: stable@vger.kernel.org" tag that was in my original submission but missing from Hao's. Since this is causing significant issues for users on kernels 6.11+ (audio interfaces failing to work), it's important this gets backported.

Hao, is this something you can do? I think the instructions at https://www.kernel.org/doc/html/v6.14/process/stable-kernel-rules.html#optio... need to be followed, but I've not done this before.

Thanks, Geoffrey.

On Fri, Mar 28, 2025 at 07:22:06AM +1030, Geoffrey D. Bennett wrote:

...

This reverts commit ccfc8948d7e4d93cab341a99774b24586717d89a.

The MediaTek Bluetooth controller reset that was added increases the Bluetooth device setup time from ~200ms to ~20s and interferes with other devices on the bus.

Three users (with Focusrite Scarlett 2nd Gen 6i6 and 3rd Gen Solo and 4i4 audio interfaces) reported that since 6.11 (which added this commit) their audio interface fails to initialise if connected during boot. Two of the users confirmed they have an MT7922.

Errors like this are observed in dmesg for the audio interface:

usb 3-4: parse_audio_format_rates_v2v3(): unable to find clock source (clock -110) usb 3-4: uac_clock_source_is_valid(): cannot get clock validity for id 41 usb 3-4: clock source 41 is not valid, cannot use

The problem only occurs when both devices and kernel modules are present and loaded during system boot, so it can be worked around by connecting the audio interface after booting.

Fixes: ccfc8948d7e4 ("Bluetooth: btusb: mediatek: reset the controller before downloading the fw") Closes: https://github.com/geoffreybennett/linux-fcp/issues/24 Bisected-by: Benedikt Ziemons ben@rs485.network Tested-by: Benedikt Ziemons ben@rs485.network Cc: stable@vger.kernel.org Signed-off-by: Geoffrey D. Bennett g@b4.vu

---

Changelog:

v1 -> v2:

• Updated commit message with additional information.
• No change to this patch's diff.
• Dropped alternate patch that only reverted for 0x7922.
• Chris, Sean, Hao agreed to reverting the change: https://lore.kernel.org/linux-bluetooth/2025031352-octopus-quadrant-f7ca@gre...

drivers/bluetooth/btmtk.c | 10 ---------- 1 file changed, 10 deletions(-)

diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c index 68846c5bd4f7..4390fd571dbd 100644 --- a/drivers/bluetooth/btmtk.c +++ b/drivers/bluetooth/btmtk.c @@ -1330,13 +1330,6 @@ int btmtk_usb_setup(struct hci_dev *hdev) break; case 0x7922: case 0x7925:

• /* Reset the device to ensure it's in the initial state before
  

•  * downloading the firmware to ensure.
  

•  */
  

• if (!test_bit(BTMTK_FIRMWARE_LOADED, &btmtk_data->flags))
  

• 	btmtk_usb_subsys_reset(hdev, dev_id);
  

• fallthrough;
  

  case 0x7961: btmtk_fw_get_filename(fw_bin_name, sizeof(fw_bin_name), dev_id, fw_version, fw_flavor);

@@ -1345,12 +1338,9 @@ int btmtk_usb_setup(struct hci_dev *hdev) btmtk_usb_hci_wmt_sync); if (err < 0) { bt_dev_err(hdev, "Failed to set up firmware (%d)", err);

• 	clear_bit(BTMTK_FIRMWARE_LOADED, &btmtk_data->flags);
  return err;
  

  }

• set_bit(BTMTK_FIRMWARE_LOADED, &btmtk_data->flags);
  

• /* It's Device EndPoint Reset Option Register */ err = btmtk_usb_uhw_reg_write(hdev, MTK_EP_RST_OPT, MTK_EP_RST_IN_OUT_OPT);

-- 2.45.0