diff options
Diffstat (limited to 'drivers/rtc/rtc-mc146818-lib.c')
| -rw-r--r-- | drivers/rtc/rtc-mc146818-lib.c | 34 |
1 files changed, 30 insertions, 4 deletions
diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c index ccd974b8a75a..d8e67a01220e 100644 --- a/drivers/rtc/rtc-mc146818-lib.c +++ b/drivers/rtc/rtc-mc146818-lib.c @@ -8,10 +8,36 @@ #include <linux/acpi.h> #endif +/* + * If the UIP (Update-in-progress) bit of the RTC is set for more then + * 10ms, the RTC is apparently broken or not present. + */ +bool mc146818_does_rtc_work(void) +{ + int i; + unsigned char val; + unsigned long flags; + + for (i = 0; i < 10; i++) { + spin_lock_irqsave(&rtc_lock, flags); + val = CMOS_READ(RTC_FREQ_SELECT); + spin_unlock_irqrestore(&rtc_lock, flags); + + if ((val & RTC_UIP) == 0) + return true; + + mdelay(1); + } + + return false; +} +EXPORT_SYMBOL_GPL(mc146818_does_rtc_work); + unsigned int mc146818_get_time(struct rtc_time *time) { unsigned char ctrl; unsigned long flags; + unsigned int iter_count = 0; unsigned char century = 0; bool retry; @@ -20,13 +46,13 @@ unsigned int mc146818_get_time(struct rtc_time *time) #endif again: - spin_lock_irqsave(&rtc_lock, flags); - /* Ensure that the RTC is accessible. Bit 6 must be 0! */ - if (WARN_ON_ONCE((CMOS_READ(RTC_VALID) & 0x40) != 0)) { - spin_unlock_irqrestore(&rtc_lock, flags); + if (iter_count > 10) { memset(time, 0, sizeof(*time)); return -EIO; } + iter_count++; + + spin_lock_irqsave(&rtc_lock, flags); /* * Check whether there is an update in progress during which the |