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[Backport v3.7-branch] drivers: watchdog: npcx: fix T0 timer reload procedure #89983

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Merged
merged 1 commit into from
Jun 18, 2025
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[Backport v3.7-branch] drivers: watchdog: npcx: fix T0 timer reload procedure #89983

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17 changes: 15 additions & 2 deletions drivers/watchdog/wdt_npcx.c
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Original file line number Diff line number Diff line change
Expand Up @@ -61,7 +61,8 @@ LOG_MODULE_REGISTER(wdt_npcx, CONFIG_WDT_LOG_LEVEL);
#define NPCX_WDT_MIN_WND_TIME 100UL

/* Timeout for reloading and restarting Timer 0. (Unit:ms) */
#define NPCX_T0CSR_RST_TIMEOUT 2
#define NPCX_T0CSR_RST_CLEAR_TIMEOUT 2
#define NPCX_T0CSR_RST_SET_TIMEOUT 1

/* Timeout for stopping watchdog. (Unit:ms) */
#define NPCX_WATCHDOG_STOP_TIMEOUT 1
Expand Down Expand Up @@ -100,10 +101,22 @@ static inline int wdt_t0out_reload(const struct device *dev)
/* Reload and restart T0 timer */
inst->T0CSR = (inst->T0CSR & ~BIT(NPCX_T0CSR_WDRST_STS)) |
BIT(NPCX_T0CSR_RST);
/*
* Wait for the T0CSR_RST bit to change from 0 to 1. This transition is expected to occur
* over multiple LFCLK cycles. If a timeout occurs, we can assume that the bit has changed
* from 0 -> 1 -> 0, but the polling thread missed it because it was preempted by
* higher-priority threads. In this case, we can simply return.
*/
st = k_uptime_get();
while (!IS_BIT_SET(inst->T0CSR, NPCX_T0CSR_RST)) {
if (k_uptime_get() - st > NPCX_T0CSR_RST_SET_TIMEOUT) {
return 0;
}
}
/* Wait for timer is loaded and restart */
st = k_uptime_get();
while (IS_BIT_SET(inst->T0CSR, NPCX_T0CSR_RST)) {
if (k_uptime_get() - st > NPCX_T0CSR_RST_TIMEOUT) {
if (k_uptime_get() - st > NPCX_T0CSR_RST_CLEAR_TIMEOUT) {
/* RST bit is still set? */
if (IS_BIT_SET(inst->T0CSR, NPCX_T0CSR_RST)) {
LOG_ERR("Timeout: reload T0 timer!");
Expand Down
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