我正在非linux操作系统上工作，现在正在尝试在Raspberry Pi 4上启用蓝牙。
我有一些必要的驱动程序，如:gpio, uart (pl011和mini-uart)，邮箱和expgpio通过那个邮箱。
启用蓝牙，我做了一些步骤:
- 我按照Linux的dts中的描述配置gpio以使UART0连接到BT/WiFi芯片;
- 我通过邮箱设置BT_ON expgpio为1(这是默认设置，只需确保);
我写了一些命令到UART0，什么也没发生=(UART驱动程序返回成功，读取命令回答总是超时。我想我可能忘记了初始化过程的一些步骤，但是正如我在Linux日志中看到的那样，只有固件下载和许多命令，例如读取设备名称，可以在它之前执行。可能我忘记启用一些时钟源或调节器，但我不知道从哪里开始我的研究。
有一部分Raspbian内核日志包含额外的调试信息:
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
提前谢谢你
对于H4协议必须使用带有硬件流控制的UART。将HFC支持添加到PL011 UART驱动程序可以解决这个问题。