NPCM Watchdog

The NPCM watchdog driver can report reset-cause information on nuvoton,npcm750-wdt and nuvoton,npcm845-wdt systems.

Userspace can read the latched reset cause through WDIOC_GETBOOTSTATUS. When CONFIG_WATCHDOG_SYSFS is enabled, the same value is also visible through /sys/class/watchdog/watchdogN/bootstatus.

The mapping is fixed in the driver. It exposes the SoC reset indications through the generic watchdog bootstatus flags and is not configurable from Device Tree.

Reset-cause mapping

Platform

Reset indication

Bootstatus flag

Reported meaning

NPCM750 and NPCM845

PORST

WDIOF_OVERHEAT

power-on reset

NPCM750 and NPCM845

CORST

WDIOF_FANFAULT

core reset

NPCM750 and NPCM845

SWR1RST

WDIOF_EXTERN1

software reset source 1

NPCM750 and NPCM845

SWR2RST

WDIOF_EXTERN2

software reset source 2

NPCM750 and NPCM845

SWR3RST

WDIOF_POWERUNDER

software reset source 3

NPCM750

SWR4RST

WDIOF_POWEROVER

software reset source 4

NPCM845

TIP reset (INTCR2[25])

WDIOF_POWEROVER

TIP reset

WDIOF_CARDRESET is reported only for the watchdog instance whose own reset-status bit is latched. On systems with three watchdog instances, this maps WD0RST, WD1RST, and WD2RST to watchdog0, watchdog1, and watchdog2 respectively.

The driver may report WDIOF_CARDRESET together with one or more of the reset-cause flags listed above.

On NPCM750, the driver samples RESSR. When reset bits are still latched, it clears them and stores the sampled value in SCRPAD2 so later watchdog probes can report the same boot-time state.

On NPCM845, the driver samples INTCR2. When reset bits are still latched, it clears them and stores the sampled value in SCRPAD10 so later watchdog probes can report the same boot-time state.

The WPCM450 watchdog continues to operate without this reset-indication mapping.