Bluetooth tty instance not showing up in /dev/tty*

KDehm · ‎2021-11-15

Hi,

I'm using a Wifi/BT module with CYW4343W chip on a custom board with STM32MP157.

When booting the system, the driver is loaded correctly and dmesg log shows

[    1.089865] 4000e000.serial: ttySTM1 at MMIO 0x4000e000 (irq = 24, base_baud = 6250000) is a stm32-usart
[    1.105124] stm32-usart 4000e000.serial: interrupt mode used for rx (no dma)
[    1.112211] stm32-usart 4000e000.serial: interrupt mode used for tx (no dma)

which indicates, that the BT UART is allocated to ttySTM1. Bluetooth is working correctly as well.

Anyway, in the userspace I can't see the ttySTM1 instance under /dev/tty*

But driver is loaded and device is shown as serial0-0:

board:~# ls -l /sys/bus/serial/devices/serial0-0/
total 0
drwxr-xr-x 3 root root    0 Nov 15 10:46 bluetooth
lrwxrwxrwx 1 root root    0 Nov 15 11:00 driver -> ../../../../../../bus/serial/drivers/hci_uart_bcm
-r--r--r-- 1 root root 4096 Nov 15 11:00 modalias
lrwxrwxrwx 1 root root    0 Nov 15 11:00 of_node -> ../../../../../../firmware/devicetree/base/soc/serial@4000e000/bluetooth
drwxr-xr-x 2 root root    0 Nov 15 11:00 power
lrwxrwxrwx 1 root root    0 Nov 15 10:46 subsystem -> ../../../../../../bus/serial
-rw-r--r-- 1 root root 4096 Nov 15 10:46 uevent

The goal is to change the baudrate of the UART connection. The appropriate tools (btattach, patchram etc.) require the correct device path.

Can anyone help?

Thanks in advance,

Kai

KDehm · ‎2021-11-15

Addendum:

Here is the output of /proc/tty/

:~# cat /proc/tty/driver/stm32-usart
serinfo:1.0 driver revision:
0: uart:stm32-usart mmio:0x40010000 irq:25 tx:19716 rx:983 RTS|CTS|DTR|DSR|CD
1: uart:stm32-usart mmio:0x4000E000 irq:24 tx:32688 rx:2621 RTS|CTS|DTR|DSR|CD

ttySTM1 (0x4000e000) is listed here as well.