From 8a0bdfd7a05f5bb0486fbe7146a2cf775957e95e Mon Sep 17 00:00:00 2001 From: David Brownell Date: Wed, 6 Feb 2008 01:38:45 -0800 Subject: rtc-cmos alarm acts as oneshot Start making the rtc-cmos alarm act more like a oneshot alarm by disabling that alarm after its IRQ fires. (ACPI hooks are also needed.) The Linux RTC framework has previously been a bit vague in this area, but any other behavior is problematic and not very portable. RTCs with full YYYY-MM-DD HH:MM[:SS] alarms won't have a problem here. Only ones with partial match criteria, with the most visible example being the PC RTC, get confused. (Because the criteria will match repeatedly.) Update comments relating to that oneshot behavior and timezone handling. (Timezones are another issue that's mostly visible with rtc-cmos. That's because PCs often dual-boot MS-Windows, which likes its RTC to match local wall-clock time instead of UTC.) Signed-off-by: David Brownell Cc: Alessandro Zummo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/rtc/rtc-cmos.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'drivers/rtc/rtc-cmos.c') diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c index ab455ddb16cf..ff7539a4dbea 100644 --- a/drivers/rtc/rtc-cmos.c +++ b/drivers/rtc/rtc-cmos.c @@ -472,10 +472,22 @@ static struct cmos_rtc cmos_rtc; static irqreturn_t cmos_interrupt(int irq, void *p) { u8 irqstat; + u8 rtc_control; spin_lock(&rtc_lock); irqstat = CMOS_READ(RTC_INTR_FLAGS); - irqstat &= (CMOS_READ(RTC_CONTROL) & RTC_IRQMASK) | RTC_IRQF; + rtc_control = CMOS_READ(RTC_CONTROL); + irqstat &= (rtc_control & RTC_IRQMASK) | RTC_IRQF; + + /* All Linux RTC alarms should be treated as if they were oneshot. + * Similar code may be needed in system wakeup paths, in case the + * alarm woke the system. + */ + if (irqstat & RTC_AIE) { + rtc_control &= ~RTC_AIE; + CMOS_WRITE(rtc_control, RTC_CONTROL); + CMOS_READ(RTC_INTR_FLAGS); + } spin_unlock(&rtc_lock); if (is_intr(irqstat)) { -- cgit v1.2.3