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path: root/drivers/rtc/rtc-mc146818-lib.c
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Diffstat (limited to 'drivers/rtc/rtc-mc146818-lib.c')
-rw-r--r--drivers/rtc/rtc-mc146818-lib.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
index 972a5b9a629d..f83c13818af3 100644
--- a/drivers/rtc/rtc-mc146818-lib.c
+++ b/drivers/rtc/rtc-mc146818-lib.c
@@ -21,6 +21,13 @@ unsigned int mc146818_get_time(struct rtc_time *time)
again:
spin_lock_irqsave(&rtc_lock, flags);
+ /* Ensure that the RTC is accessible. Bit 0-6 must be 0! */
+ if (WARN_ON_ONCE((CMOS_READ(RTC_VALID) & 0x7f) != 0)) {
+ spin_unlock_irqrestore(&rtc_lock, flags);
+ memset(time, 0xff, sizeof(*time));
+ return 0;
+ }
+
/*
* Check whether there is an update in progress during which the
* readout is unspecified. The maximum update time is ~2ms. Poll