stm32mp1 reading the reset status watchdog driver

[Ara.1]

Hi

In my application we need to read the last rest status, whether its a POR or WDOG

      ret = ioctl(wdog, WDIOC_GETBOOTSTATUS, &status);

looks like this support is not available in

drivers/watchdog/stm32_iwdg.c

can anyone tell me how add a patch in stm32mp1 board ?

[Ara.1]

any one faced this scenario ?

[Kevin HUBER · Accepted solution]

Hi @Ara.1​ 

Since your need seems to know if the last reset occurs because of POR of WDOG, something else seems more adapted to you.

I advise you to take a look in the sources of the TF-A at the function: "print_reset_reason"

This function is available in the file "plat/st/stm32mp1/bl2_plat_setup.c" and displays the reason of the reset by reading the register RCC_MP_RSTSCLRR

static void print_reset_reason(void)
{
	uint32_t rstsr = mmio_read_32(stm32mp_rcc_base() + RCC_MP_RSTSCLRR);
 
	if (rstsr == 0U) {
		WARN("Reset reason unknown\n");
		return;
	}
 
	INFO("Reset reason (0x%x):\n", rstsr);
	if ((rstsr & RCC_MP_RSTSCLRR_PADRSTF) == 0U) {
		if ((rstsr & RCC_MP_RSTSCLRR_STDBYRSTF) != 0U) {
			INFO("System exits from STANDBY\n");
			return;
		}

This register is accessible from application, so you can read its value.

To make a test on your board, you can try to read the register by using devmem. Details to install and use it are on the wiki: https://wiki.st.com/stm32mpu/wiki/How_to_read_or_write_peripheral_registers#Installing_Devmem_on_your_target_board

The address to read is the one read in "print_reset_reason",

stm32mp_rcc_base() + RCC_MP_RSTSCLRR

on my board STM32MP157F-DK2 with the developer package, the address is:

#define RCC_BASE			U(0x50000000)

+

#define RCC_MP_RSTSCLRR			U(0x408)

So the final address is 0x5000408

Once you use devmem, you get the value like this:

 

Then you interpret this value by using the reference manual that details all the possible values: https://www.st.com/resource/en/reference_manual/rm0436-stm32mp157-advanced-armbased-32bit-mpus-stmicroelectronics.pdf#page=996

Hope it help you,

Regards,

Kevin

[Olivier GALLIEN]

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