Bluetooth on raspberry 4 without Linux

Question

I'm working on non-Linux OS and now trying to enable bluetooth on Raspberry Pi 4.

I have some necessary drivers such as: gpio, uart (pl011 and mini-uart), mailbox and expgpio through that mailbox.

To enable bluetooth I make some steps:

• I configure GPIOs as described in Linux's dts to make UART0 connected to BT/WiFi chip;
• I set BT_ON expgpio to 1 through mailbox (it is made by default, just ensure);

I wrote some command to UART0 and nothing happened =( UART driver return success and reading command answer is always timeouted. I think I could forget some step for initialization procedure, but as I can see in Linux log there is only firmware downloading and many commands, such as read device name, can be executed prior to it. May be I forget to enable some clock source or a regulator, but I don't have any idea where start my research.

There is a part of Raspbian kernel log with additional debug info:

Jan 28 05:17:13 raspberrypi kernel: [   15.321055] Bluetooth: Core ver 2.22
Jan 28 05:17:13 raspberrypi kernel: [   15.321093] device class 'bluetooth': registering
Jan 28 05:17:13 raspberrypi kernel: [   15.321149] NET: Registered PF_BLUETOOTH protocol family
Jan 28 05:17:13 raspberrypi kernel: [   15.321158] Bluetooth: HCI device and connection manager initialized
Jan 28 05:17:13 raspberrypi kernel: [   15.321176] Bluetooth: HCI socket layer initialized
Jan 28 05:17:13 raspberrypi kernel: [   15.321189] Bluetooth: L2CAP socket layer initialized
Jan 28 05:17:13 raspberrypi kernel: [   15.321208] Bluetooth: SCO socket layer initialized
Jan 28 05:17:13 raspberrypi kernel: [   15.335356] Bluetooth: HCI UART driver ver 2.3
Jan 28 05:17:13 raspberrypi kernel: [   15.335377] Bluetooth: HCI UART protocol H4 registered at id 0
Jan 28 05:17:13 raspberrypi kernel: [   15.335387] bus: 'serial': add driver hci_uart_h5
Jan 28 05:17:13 raspberrypi kernel: [   15.335456] Bluetooth: HCI UART protocol Three-wire (H5) registered at id 2
Jan 28 05:17:13 raspberrypi kernel: [   15.335480] bus: 'platform': add driver hci_bcm
Jan 28 05:17:13 raspberrypi kernel: [   15.335641] bus: 'serial': add driver hci_uart_bcm
Jan 28 05:17:13 raspberrypi kernel: [   15.335679] Bluetooth: HCI UART protocol Broadcom registered at id 7
Jan 28 05:17:13 raspberrypi kernel: [   15.337922] Bluetooth: TTY name ttyAMA0
Jan 28 05:17:13 raspberrypi kernel: [   15.338543] Bluetooth: hci_uart_register_dev
Jan 28 05:17:13 raspberrypi kernel: [   15.338599] device: 'hci0': device_add
Jan 28 05:17:13 raspberrypi kernel: [   15.345358] device: 'rfkill1': device_add
Jan 28 05:17:13 raspberrypi kernel: [   15.345497] Bluetooth: HCI UART protocol set. Proto H4; id 0
Jan 28 05:17:13 raspberrypi kernel: [   15.345530] Bluetooth: hci_uart_open hci0 5d898f04
Jan 28 05:17:13 raspberrypi kernel: [   15.345543] Bluetooth: hci_uart_setup: START
Jan 28 05:17:13 raspberrypi kernel: [   15.345550] Bluetooth: hci_uart_setup: init speed = 0
Jan 28 05:17:13 raspberrypi kernel: [   15.345557] Bluetooth: hci_uart_setup: oper speed = 0
Jan 28 05:17:13 raspberrypi kernel: [   15.352975] Bluetooth: hci0: type 1 len 3
Jan 28 05:17:13 raspberrypi kernel: [   15.353010] Bluetooth skb:   00000000: 01 03 10 00
Jan 28 05:17:13 raspberrypi kernel: [   15.353026] Bluetooth: hci_uart_write_work written 4
Jan 28 05:17:13 raspberrypi kernel: [   15.353760] Bluetooth: hci0: type 1 len 3
Jan 28 05:17:13 raspberrypi kernel: [   15.353826] Bluetooth skb:   00000000: 01 01 10 00
....
a lot of lines
....
Jan 28 05:17:13 raspberrypi btuart[479]: bcm43xx_init
Jan 28 05:17:13 raspberrypi btuart[479]: Flash firmware /lib/firmware/brcm/BCM4345C0.hcd
Jan 28 05:17:13 raspberrypi btuart[479]: Set Controller UART speed to 3000000 bit/s
Jan 28 05:17:13 raspberrypi btuart[479]: Device setup complete
Jan 28 05:17:13 raspberrypi systemd[1]: Starting Load/Save RF Kill Switch Status...
Jan 28 05:17:13 raspberrypi systemd[1]: Started Configure Bluetooth Modems connected by UART.
Jan 28 05:17:13 raspberrypi systemd[1]: Reached target Multi-User System.
Jan 28 05:17:13 raspberrypi systemd[1]: Reached target Graphical Interface.
Jan 28 05:17:13 raspberrypi systemd[1]: Starting Update UTMP about System Runlevel Changes...
Jan 28 05:17:13 raspberrypi systemd[625]: Reached target Bluetooth.
Jan 28 05:17:13 raspberrypi systemd[1]: Started Load/Save RF Kill Switch Status.
Jan 28 05:17:13 raspberrypi systemd[1]: Created slice system-bthelper.slice.
Jan 28 05:17:13 raspberrypi systemd[1]: Starting Raspberry Pi bluetooth helper...
Jan 28 05:17:13 raspberrypi systemd[1]: systemd-update-utmp-runlevel.service: Succeeded.
Jan 28 05:17:13 raspberrypi systemd[1]: Finished Update UTMP about System Runlevel Changes.
Jan 28 05:17:13 raspberrypi bthelper[774]: Raspberry Pi BDADDR already set
Jan 28 05:17:13 raspberrypi systemd[1]: Finished Raspberry Pi bluetooth helper.
Jan 28 05:17:13 raspberrypi kernel: [   15.490868] Bluetooth: hci0: type 1 len 8
Jan 28 05:17:13 raspberrypi kernel: [   15.490909] Bluetooth skb:   00000000: 01 1c fc 05 01 02 00 01 01
Jan 28 05:17:13 raspberrypi kernel: [   15.490930] Bluetooth: hci_uart_write_work written 9

Thank you in advance

Answer 1

For H4 protocol UART with Hardware Flow Control must be used. Adding HFC support to PL011 UART driver resolves the problem.