npcx: ensure we don't unlock watchdog too soon

We cannot unlock the watchdog timer with 3 watch dog ticks of touching
it per the datasheet. This is actually around 100ms so we should protect
against this.

BRANCH=none
BUG=b:140207603
TEST=eliminates cold reset issue.

Change-Id: Iaef59dad9f5640d64d5d430aea87bd16c2efd30d
Signed-off-by: Jett Rink <jettrink@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1790302
Reviewed-by: Scott Collyer <scollyer@chromium.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: ML Chao <mlchao@nuvoton.corp-partner.google.com>
Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Tested-by: Furquan Shaikh <furquan@chromium.org>
Commit-Queue: Furquan Shaikh <furquan@chromium.org>

4 files changed, 32 insertions, 13 deletions

diff --git a/chip/npcx/spiflashfw/npcx_monitor.c b/chip/npcx/spiflashfw/npcx_monitor.c
index a0b011476d..cc327e3440 100644
--- a/chip/npcx/spiflashfw/npcx_monitor.c
+++ b/chip/npcx/spiflashfw/npcx_monitor.c
@@ -287,9 +287,7 @@ sspi_flash_upload(int spi_offset, int spi_size)
 	}
 
 	/* Unlock & stop watchdog */
-	NPCX_WDSDM = 0x87;
-	NPCX_WDSDM = 0x61;
-	NPCX_WDSDM = 0x63;
+	watchdog_stop_and_unlock();
 
 	/* UMA Unlock */
 	CLEAR_BIT(NPCX_UMA_ECTS, NPCX_UMA_ECTS_UMA_LOCK);
diff --git a/chip/npcx/system.c b/chip/npcx/system.c
index ff18334533..e7895dc3dc 100644
--- a/chip/npcx/system.c
+++ b/chip/npcx/system.c
@@ -44,9 +44,7 @@
 void system_watchdog_reset(void)
 {
 	/* Unlock & stop watchdog registers */
-	NPCX_WDSDM = 0x87;
-	NPCX_WDSDM = 0x61;
-	NPCX_WDSDM = 0x63;
+	watchdog_stop_and_unlock();
 
 	/* Reset TWCFG */
 	NPCX_TWCFG = 0;
@@ -500,9 +498,7 @@ void __enter_hibernate(uint32_t seconds, uint32_t microseconds)
 	CLEAR_BIT(NPCX_ITCTS(ITIM_WDG_NO), NPCX_ITCTS_ITEN);
 
 	/* Unlock & stop watchdog */
-	NPCX_WDSDM = 0x87;
-	NPCX_WDSDM = 0x61;
-	NPCX_WDSDM = 0x63;
+	watchdog_stop_and_unlock();
 
 	/* Initialize watchdog */
 	NPCX_TWCFG = 0; /* Select T0IN clock as watchdog prescaler clock */
diff --git a/chip/npcx/system_chip.h b/chip/npcx/system_chip.h
index 5ca686a86f..2836a1e4f7 100644
--- a/chip/npcx/system_chip.h
+++ b/chip/npcx/system_chip.h
@@ -30,9 +30,12 @@ enum bbram_data_index {
 	BBRM_DATA_INDEX_PANIC_BKUP = 36,       /* Panic data (index 35-63)*/
 };
 
-/* Issue a watchdog reset*/
+/* Issue a watchdog reset */
 void system_watchdog_reset(void);
 
+/* Stops the watchdog timer and unlocks configuration. */
+void watchdog_stop_and_unlock(void);
+
 /*
  * Configure the specific memory addresses in the the MPU
  * (Memory Protection Unit) for Nuvoton different chip series.
diff --git a/chip/npcx/watchdog.c b/chip/npcx/watchdog.c
index 44a980326b..233c875643 100644
--- a/chip/npcx/watchdog.c
+++ b/chip/npcx/watchdog.c
@@ -58,6 +58,27 @@ static uint8_t watchdog_count(void)
 	return cnt;
 }
 
+static timestamp_t last_watchdog_touch;
+void watchdog_stop_and_unlock(void)
+{
+	/*
+	 * Ensure we have waited at least 3 watchdog ticks since touching WD
+	 * timer. 3 / (32768 / 1024) HZ = 93.75ms
+	 */
+	while (time_since32(last_watchdog_touch) < (100 * MSEC))
+		continue;
+
+	NPCX_WDSDM = 0x87;
+	NPCX_WDSDM = 0x61;
+	NPCX_WDSDM = 0x63;
+}
+
+static void touch_watchdog_count(void)
+{
+	NPCX_WDSDM = 0x5C;
+	last_watchdog_touch = get_time();
+}
+
 void __keep watchdog_check(uint32_t excep_lr, uint32_t excep_sp)
 {
 	int  wd_cnt;
@@ -75,7 +96,8 @@ void __keep watchdog_check(uint32_t excep_lr, uint32_t excep_sp)
 		 * Touch watchdog to let UART have enough time
 		 * to print panic info
 		 */
-		NPCX_WDSDM = 0x5C;
+		touch_watchdog_count();
+
 		/* Print panic info */
 		watchdog_trace(excep_lr, excep_sp);
 		cflush();
@@ -112,7 +134,7 @@ void watchdog_reload(void)
 
 #if 1 /* mark this for testing watchdog */
 	/* Touch watchdog & reset software counter */
-	NPCX_WDSDM = 0x5C;
+	touch_watchdog_count();
 #endif
 
 	/* Enable watchdog interrupt */
@@ -125,7 +147,7 @@ int watchdog_init(void)
 #if SUPPORT_WDG
 	/* Touch watchdog before init if it is already running */
 	if (IS_BIT_SET(NPCX_T0CSR, NPCX_T0CSR_WD_RUN))
-		NPCX_WDSDM = 0x5C;
+		touch_watchdog_count();
 
 	/* Keep prescaler ratio timer0 clock to 1:1024 */
 	NPCX_TWCP = 0x0A;