From f44f7f96a20af16f6f12e1c995576d6becf5f57b Mon Sep 17 00:00:00 2001 From: John Stultz Date: Mon, 21 Feb 2011 22:58:51 -0800 Subject: RTC: Initialize kernel state from RTC Mark Brown pointed out a corner case: that RTC alarms should be allowed to be persistent across reboots if the hardware supported it. The rework of the generic layer to virtualize the RTC alarm virtualized much of the alarm handling, and removed the code used to read the alarm time from the hardware. Mark noted if we want the alarm to be persistent across reboots, we need to re-read the alarm value into the virtualized generic layer at boot up, so that the generic layer properly exposes that value. This patch restores much of the earlier removed rtc_read_alarm code and wires it in so that we set the kernel's alarm value to what we find in the hardware at boot time. NOTE: Not all hardware supports persistent RTC alarm state across system reset. rtc-cmos for example will keep the alarm time, but disables the AIE mode irq. Applications should not expect the RTC alarm to be valid after a system reset. We will preserve what we can, to represent the hardware state at boot, but its not guarenteed. Further, in the future, with multiplexed RTC alarms, the soonest alarm to fire may not be the one set via the /dev/rt ioctls. So an application may set the alarm with RTC_ALM_SET, but after a reset find that RTC_ALM_READ returns an earlier time. Again, we preserve what we can, but applications should not expect the RTC alarm state to persist across a system reset. Big thanks to Mark for pointing out the issue! Thanks also to Marcelo for helping think through the solution. CC: Mark Brown CC: Marcelo Roberto Jimenez CC: Thomas Gleixner CC: Alessandro Zummo CC: rtc-linux@googlegroups.com Reported-by: Mark Brown Signed-off-by: John Stultz --- drivers/rtc/class.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'drivers/rtc/class.c') diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c index c404b61386b..09b4437b3e6 100644 --- a/drivers/rtc/class.c +++ b/drivers/rtc/class.c @@ -117,6 +117,7 @@ struct rtc_device *rtc_device_register(const char *name, struct device *dev, struct module *owner) { struct rtc_device *rtc; + struct rtc_wkalrm alrm; int id, err; if (idr_pre_get(&rtc_idr, GFP_KERNEL) == 0) { @@ -166,6 +167,12 @@ struct rtc_device *rtc_device_register(const char *name, struct device *dev, rtc->pie_timer.function = rtc_pie_update_irq; rtc->pie_enabled = 0; + /* Check to see if there is an ALARM already set in hw */ + err = __rtc_read_alarm(rtc, &alrm); + + if (!err && !rtc_valid_tm(&alrm.time)) + rtc_set_alarm(rtc, &alrm); + strlcpy(rtc->name, name, RTC_DEVICE_NAME_SIZE); dev_set_name(&rtc->dev, "rtc%d", id); -- cgit v1.2.3