hello AlexCo,
please download Cboot Sources T186 via https://developer.nvidia.com/embedded/linux-tegra.
you should check below for the PMIC reset reasons.
for example,
$L4T_Sources/r32.6.1/Linux_for_Tegra/source/public/cboot/bootloader/partner/t18x/common/lib/linuxboot/t186/linuxboot_helper.c
char *pmic_reset_reason_table[] = {
"NIL_OR_MORE_THAN_1_BIT",
"SHDN", /* B0 */
"WDOG",
"HDRST",
"TOVLD",
"MBSLD",
"MBO",
"MBU",
"RSTIN", /* B7 */
};