[Bug 220990] New: hci_uart_bcm: BCM43341 on Intel Atom (serdev) fails init (MTU 0:0, DOWN RAW)

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=220990

            Bug ID: 220990
           Summary: hci_uart_bcm: BCM43341 on Intel Atom (serdev) fails
                    init (MTU 0:0, DOWN RAW)
           Product: Drivers
           Version: 2.5
          Hardware: Intel
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: Bluetooth
          Assignee: linux-bluetooth@vger.kernel.org
          Reporter: bugzilla@emircanerkul.com
        Regression: No

Created attachment 309211
  --> https://bugzilla.kernel.org/attachment.cgi?id=309211&action=edit
fix for llm models

I applied solution in https://bugzilla.kernel.org/show_bug.cgi?id=100461

But now it do not detect my devices.

❯ bluetoothctl              
hci0 new_settings: powered bondable ssp br/edr le secure-conn 
Agent registered
[CHG] Controller CD:74:2E:6E:CD:FA Pairable: yes
[bluetoothctl]> power on
Changing power on succeeded
[bluetoothctl]> discover on
Invalid command in menu main: discover

Use "help" for a list of available commands in a menu.
Use "menu <submenu>" if you want to enter any submenu.
Use "back" if you want to return to menu main.
[bluetoothctl]> he
[bluetoothctl]> scan on
SetDiscoveryFilter success
hci0 type 7 discovering on
Discovery started
[CHG] Controller CD:74:2E:6E:CD:FA Discovering: yes
hci0 type 7 discovering off
hci0 type 7 discovering on
hci0 type 7 discovering off
hci0 type 7 discovering on
hci0 type 7 discovering off

--- ISSUE SOVED WITH 100461 ---

1. Hardware Description
Device: Intel StickPC (Atom x5-Z8300 "Cherry Trail" / "Bay Trail" platform)
Bluetooth/WiFi Chip: Broadcom BCM43341B0 (Combo Chip)
ACPI ID: BCM2E95
Interface: Intel HS-UART connected via serdev (serial0-0)
Connection: UART (not USB)


2. System Information
OS: Debian 13 (Trixie)
Kernel: 6.12.63+deb13-amd64 (Upstream 6.12 series)
BlueZ Version: 5.82
Firmware: BCM43341B0.hcd (Size: 41,333 bytes).
Verified identical to working Windows 10 driver firmware.


3. Issue Description
The Bluetooth controller is detected, and the hci_uart_bcm driver successfully
loads the specific firmware patch (build 0176). However, immediately after
firmware loading, the device remains in a DOWN RAW state with MTU 0:0.
Attempting to bring the device up fails with "Operation not supported". The
device never registers with the BlueZ management layer (btmgmt info is empty).
It appears the HCI_QUIRK_RAW_DEVICE flag (set by hci_serdev.c during setup) is
never cleared, or the bcm_setup function completes but the driver fails to
transition the device to a fully operational state.


4. Steps to Reproduce
Boot minimal Debian 13 with Kernel 6.12 on Intel Atom Z8300 device with
BCM43341.
Ensure correct firmware BCM43341B0.hcd is in /lib/firmware/brcm/.
Check hciconfig -a.


5. Logs & Output
hciconfig -a
hci0:   Type: Primary  Bus: UART
        BD Address: 43:34:1B:00:1F:AC  ACL MTU: 0:0  SCO MTU: 0:0
        DOWN RAW 
        RX bytes:2220 acl:0 sco:0 events:238 errors:0
        TX bytes:41654 acl:0 sco:0 commands:238 errors:0
        Features: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
        Packet type: DM1 DH1 HV1 
        Link policy: 
        Link mode: PERIPHERAL ACCEPT
(Note: Address is the default Broadcom address, indicating configuration didn't
finish)
dmesg (Filtered)
[   10.438792] hci_uart_bcm serial0-0: supply vbat not found, using dummy
regulator
[   10.438896] hci_uart_bcm serial0-0: supply vddio not found, using dummy
regulator
...
[   10.888224] Bluetooth: hci0: BCM: chip id 82
[   10.902831] Bluetooth: hci0: BCM43341B0
[   10.902851] Bluetooth: hci0: BCM43341B0 (002.001.014) build 0000
[   10.929324] Bluetooth: hci0: BCM43341B0 'brcm/BCM43341B0.hcd' Patch
...
[   11.551231] Bluetooth: hci0: BCM43341B0 37.4 MHz Class 1 WLBGA iTR
[   11.551245] Bluetooth: hci0: BCM43341B0 (002.001.014) build 0176
[   11.552167] Bluetooth: hci0: BCM: Using default device address
(43:34:1b:00:1f:ac)
(Note: Firmware loads successfully - build number changes from 0000 to 0176.
But then it stops.)
btmgmt info
Index list with 0 items
Attempting to bring up
# hciconfig hci0 up
Can't init device hci0: Operation not supported (95)


6. What Was Tried (Workarounds)
Windows Firmware: Replaced Linux firmware with verified working Windows 10
driver (BCM43341B0_002.001.014.0122.0176.hcd). Result: Identical behavior.
Firmware load OK, Init fail.
Kernel Parameters: Added intel_idle.max_cstate=1 to prevent BayTrail deep sleep
issues. Result: No change.
btattach: Attempted manual btattach but failed because serdev framework claims
the UART (serial0-0) and does not expose a /dev/ttyS* node to userspace even
after unbinding the driver.


7. Suspected Root Cause
Regression in drivers/bluetooth/hci_bcm.c or hci_serdev.c on Kernel 6.12
regarding the handling of HCI_QUIRK_RAW_DEVICE for ACPI-enumerated BCM devices.
The setup phase (firmware load) works, but the transition to operational mode
is missing.

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