This change adds support for WDIOC_GETTIMELEFT so userspace
programs can get the number of seconds before system reset by
the watchdog timer via ioctl.
Signed-off-by: Pohsun Su <pohsuns@xxxxxxxxxx>
---
drivers/clocksource/timer-tegra186.c | 41 ++++++++++++++++++++++++++++
1 file changed, 41 insertions(+)
diff --git a/drivers/clocksource/timer-tegra186.c b/drivers/clocksource/timer-tegra186.c
index 304537dadf2c..685c6689a2da 100644
--- a/drivers/clocksource/timer-tegra186.c
+++ b/drivers/clocksource/timer-tegra186.c
@@ -29,6 +29,7 @@
#define TMRSR 0x004
#define TMRSR_INTR_CLR BIT(30)
+#define TMRSR_PCV GENMASK(28, 0)
#define TMRCSSR 0x008
#define TMRCSSR_SRC_USEC (0 << 0)
@@ -45,6 +46,9 @@
#define WDTCR_TIMER_SOURCE_MASK 0xf
#define WDTCR_TIMER_SOURCE(x) ((x) & 0xf)
+#define WDTSR 0x004
+#define WDTSR_CURRENT_EXPIRATION_COUNT GENMASK(14, 12)
+
#define WDTCMDR 0x008
#define WDTCMDR_DISABLE_COUNTER BIT(1)
#define WDTCMDR_START_COUNTER BIT(0)
@@ -234,12 +238,49 @@ static int tegra186_wdt_set_timeout(struct watchdog_device *wdd,
return 0;
}
+static unsigned int tegra186_wdt_get_timeleft(struct watchdog_device *wdd)
+{
+ struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);
+ u32 timeleft;
+ u32 expiration;
+
+ if (!watchdog_active(&wdt->base)) {
+ /* return zero if the watchdog timer is not activated. */
+ return 0;
+ }
+
+ /*
+ * System power-on reset occurs on the fifth expiration of the watchdog timer and so
+ * when the watchdog timer is configured, the actual value programmed into the counter
+ * is 1/5 of the timeout value. Once the counter reaches 0, expiration count will be
+ * increased by 1 and the down counter restarts.
+ * Hence to get the time left before system reset we must combine 2 parts:
+ * 1. value of the current down counter
+ * 2. (number of counter expirations remaining) * (timeout/5)
+ */
+
+ /* Get the current number of counter expirations. Should be a value between 0 and 4. */
+ expiration = FIELD_GET(WDTSR_CURRENT_EXPIRATION_COUNT, readl_relaxed(wdt->regs + WDTSR));
+
+ /* Convert the current counter value to seconds, rounding up to the nearest second. */
+ timeleft = FIELD_GET(TMRSR_PCV, readl_relaxed(wdt->tmr->regs + TMRSR));
+ timeleft = (timeleft + USEC_PER_SEC / 2) / USEC_PER_SEC;
+
+ /*
+ * Calculate the time remaining by adding the time for the counter value
+ * to the time of the counter expirations that remain.
+ */
+ timeleft += wdt->base.timeout * (4 - expiration) / 5;
+ return timeleft;
+}
+
static const struct watchdog_ops tegra186_wdt_ops = {
.owner = THIS_MODULE,
.start = tegra186_wdt_start,
.stop = tegra186_wdt_stop,
.ping = tegra186_wdt_ping,
.set_timeout = tegra186_wdt_set_timeout,
+ .get_timeleft = tegra186_wdt_get_timeleft,
};
static struct tegra186_wdt *tegra186_wdt_create(struct tegra186_timer *tegra,
--
2.17.1
