zephyr stm32f4 startup freezes at startup in PRINT_BOOT_BANNER() #stm32 #uart #boot

[StefJar]

After pulling latest commit(7c290b0), the startup hangs when printing chars to the UART.

Call stack trace:

uart_stm32_poll_out() at uart_stm32.c:59 0x8007dd2	
_impl_uart_poll_out() at uart.h:257 0x8006024	
uart_poll_out() at uart.h:17 0x8006024	
console_out() at uart_console.c:110 0x8006024	
char_out() at printk.c:265 0x8002a72	
_vprintk() at printk.c:103 0x8002e2e	
vprintk() at printk.c:290 0x8002e54	
printk() at printk.c:340 0x8002e6e	
bg_thread_main() at init.c:215 0x8008252	
_thread_entry() at thread_entry.c:29 0x80025c0	
_Cstart() at init.c:485 0x80082b8	
__config_i2c_stm32_1() at 0x8009780	

hang at uart_stm32.c in

static unsigned char uart_stm32_poll_out(struct device *dev,
					unsigned char c)
{
	USART_TypeDef *UartInstance = UART_STRUCT(dev);

	/* Wait for TXE flag to be raised */
>>>	while (!LL_USART_IsActiveFlag_TXE(UartInstance))
		;

	LL_USART_ClearFlag_TC(UartInstance);

this function is called from init.c:

static void bg_thread_main(void *unused1, void *unused2, void *unused3)
{
...
PRINT_BOOT_BANNER();
...

I am using the a slightly different version of the

with following dts changes:

	chosen {
		zephyr,console = &usart1;
		zephyr,sram = &sram0;
		zephyr,flash = &flash0;
	};
	
	soc {
		pinctrl: pin-controller@40020000 {
			usart1_pins_d: usart1_3 {
				rx_tx {
					rx = <STM32_PIN_PA10 (STM32_PINMUX_ALT_FUNC_7 | STM32_PUPDR_NO_PULL)>;
					tx = <STM32_PIN_PA15 (STM32_PINMUX_ALT_FUNC_7 | STM32_PUSHPULL_PULLUP)>;
				};
			};
...

&usart1 {
	current-speed = <115200>;
	pinctrl-0 = <&usart1_pins_d>;
	pinctrl-names = "default";
	status = "ok";
};

[erwango]

@StefJar

What was your previous sha1?
What board are you using?
Do you mean that banner does not print correctly in eg hello_world?

[StefJar]

@sha1 sorry I don't know the exactly one. Guess the last form Friday(09-11-2018).
@board: a custom board. It's comparable to the nucleo_f412zg BUT I redirected the console form uart3 to uart1. these uart1 has a different pin use. That's why I added the usart1_pins_d node to the pin control
@PRINT_BOOT_BANNER(): this prints the boot message of zephyr os like version & hash

[StefJar]

Maybe commit : 6d1a31b
or bd73879 breaks the power up sequence

To make it clear. The PRINT_BOOT_BANNER function is called at the starting of the main thread/kernel. It loops now infinite in the uart_stm32_poll_out function

[erwango]

ok, I think I got the issue.
Looks like a clock configuration issue in dts.
In dts/arm/st/f4/stm32f4.dtsi, can you try the following change:

 		usart1: serial@40011000 {
 			compatible = "st,stm32-usart", "st,stm32-uart";
 			reg = <0x40011000 0x400>;
-			clocks = <&rcc STM32_CLOCK_BUS_APB2 0x00004000>;
+			clocks = <&rcc STM32_CLOCK_BUS_APB2 0x00000010>;
 			interrupts = <37 0>;
 			status = "disabled";
 			label = "UART_1";
 		};

[StefJar]

I can confirm that the clock change to
clocks = <&rcc STM32_CLOCK_BUS_APB2 0x00000010>;
solves that issue

[avisconti]

Verified the proposed fix also on ArgonKey board.
Thx!