SCFW: Enable PMIC external watchdog for iMX8QXP MEK

[#1]

Attachched is the reference patch to enable the PMIC external watchdog in SCFW, it is based on SCFW porting kit v1.1.2 from NXP website: https://www.nxp.com/webapp/Download?colCode=L4.14.78_1.0.0_SCFWKIT&appType=license&location=null

Please apply the patches to "imx-scfw-porting-kit-1.1.2/src/scfw_export_mx8qx_b0"

On iMX8QXP MEK board, the patches will enable the PF8100 watchdog by macro "#define ENABLE_PMIC_EXTERNAL_WDOG", and it will refresh the watchdog timer by I2C interface.

The default timeout value is 0xD for 8192ms (#define PMIC_EXTERNAL_WDOG_TIMEOUT  0xD), and SCFW will refresh it with 1000ms period (board_pmic_wdog_refresh_period_ms = 1000U).

When the iMX8 system goto low power mode, it will pull SCU_PMIC_STANDBY to notify the PMIC, then PMIC will switch to suspend mode too, during PMIC suspend mode, this watchdog timer is off too. It will restart after PMIC resume to normal mode.

Without PMIC OTP burning for WDOG, the current setting of patch will trigger hard reset after PMIC WDOG is timeout.

0001-scfw-add-board-board-tick.patch

This patch is used to added polling ticket in board.c, after SCFW running, it will call board_tick() with 10ms period. In future SCFW release, this patch is not needed to apply, it is in default code, only when SCFW porting kit version is 1.1.2 and early version, you need apply this patch.

0002-scfw-enable-pmic-external-wdog.patch

This is the reference patch to enable the PF8100 watchdog timer and refresh code. iMX8QXP MEK is used as the example.

Note:

In default SCFW, it had already used internel watchdog to make sure SCFW is always running, if SCFW is built as no debug version (M=0 D=0), all SCFW halt will cause SOC reset. And if hardware had connected the SCU_WDOG_OUT pin from iMX8QXP to PMIC's WDI pin, then during SOC reset, the PMIC will also do hard reset to make a POR reboot for the whole system.