diff options
Diffstat (limited to 'drivers/rtc/rtc-mc146818-lib.c')
| -rw-r--r-- | drivers/rtc/rtc-mc146818-lib.c | 7 |
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 |