[PATCH] rtc: disallow update interrupts when time is invalid

[Alexandre Belloni <alexandre.belloni@bootlin.com>]

Never enable update interrupts when the time set on the rtc is invalid.
In that case, also avoid enabling the emulation because it will fail for
the same reason.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
---
 drivers/rtc/interface.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index f8b7c004d6ec..bd8034b7bc93 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -545,7 +545,7 @@ EXPORT_SYMBOL_GPL(rtc_alarm_irq_enable);
 
 int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
 {
-	int err;
+	int rc = 0, err;
 
 	err = mutex_lock_interruptible(&rtc->ops_lock);
 	if (err)
@@ -570,7 +570,9 @@ int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
 		struct rtc_time tm;
 		ktime_t now, onesec;
 
-		__rtc_read_time(rtc, &tm);
+		rc = __rtc_read_time(rtc, &tm);
+		if (rc)
+			goto out;
 		onesec = ktime_set(1, 0);
 		now = rtc_tm_to_ktime(tm);
 		rtc->uie_rtctimer.node.expires = ktime_add(now, onesec);
@@ -582,6 +584,16 @@ int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
 
 out:
 	mutex_unlock(&rtc->ops_lock);
+
+	/*
+	 * __rtc_read_time() failed, this probably means that the RTC time has
+	 * never been set or less probably there is a transient error on the
+	 * bus. In any case, avoid enabling emulation has this will fail when
+	 * reading the time too.
+	 */
+	if (rc)
+		return rc;
+
 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
 	/*
 	 * Enable emulation if the driver returned -EINVAL to signal that it has
-- 
2.21.0