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 c404b61386bf..09b4437b3e61 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 From f6d5b33125c4fa63c16f7f54c533338c9695d82c Mon Sep 17 00:00:00 2001 From: John Stultz Date: Tue, 29 Mar 2011 18:00:27 -0700 Subject: RTC: Fix early irqs caused by calling rtc_set_alarm too early When we register an rtc device at boot, we read the alarm value in hardware and set the rtc device's aie_timer to that value. The initial method to do this was to simply call rtc_set_alarm() with the value read from hardware. However, this may cause problems as rtc_set_alarm may enable interupts, and the RTC alarm might fire, which can cause invalid pointer dereferencing since the RTC registration is not complete. This patch solves the issue by initializing the rtc_device.aie_timer y hand via rtc_initialize_alarm(). This avoids any calls to the RTC hardware which might enable interrupts too early. CC: Thomas Gleixner CC: Alessandro Zummo Reported-by: Konrad Rzeszutek Wilk Tested-by: Konrad Rzeszutek Wilk Signed-off-by: John Stultz --- drivers/rtc/class.c | 2 +- drivers/rtc/interface.c | 26 ++++++++++++++++++++++++++ include/linux/rtc.h | 2 ++ 3 files changed, 29 insertions(+), 1 deletion(-) (limited to 'drivers/rtc/class.c') diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c index 09b4437b3e61..39013867cbd6 100644 --- a/drivers/rtc/class.c +++ b/drivers/rtc/class.c @@ -171,7 +171,7 @@ struct rtc_device *rtc_device_register(const char *name, struct device *dev, err = __rtc_read_alarm(rtc, &alrm); if (!err && !rtc_valid_tm(&alrm.time)) - rtc_set_alarm(rtc, &alrm); + rtc_initialize_alarm(rtc, &alrm); strlcpy(rtc->name, name, RTC_DEVICE_NAME_SIZE); dev_set_name(&rtc->dev, "rtc%d", id); diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c index 8ec6b069a7f5..b2fea80dfb65 100644 --- a/drivers/rtc/interface.c +++ b/drivers/rtc/interface.c @@ -375,6 +375,32 @@ int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm) } EXPORT_SYMBOL_GPL(rtc_set_alarm); +/* Called once per device from rtc_device_register */ +int rtc_initialize_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm) +{ + int err; + + err = rtc_valid_tm(&alarm->time); + if (err != 0) + return err; + + err = mutex_lock_interruptible(&rtc->ops_lock); + if (err) + return err; + + rtc->aie_timer.node.expires = rtc_tm_to_ktime(alarm->time); + rtc->aie_timer.period = ktime_set(0, 0); + if (alarm->enabled) { + rtc->aie_timer.enabled = 1; + timerqueue_add(&rtc->timerqueue, &rtc->aie_timer.node); + } + mutex_unlock(&rtc->ops_lock); + return err; +} +EXPORT_SYMBOL_GPL(rtc_initialize_alarm); + + + int rtc_alarm_irq_enable(struct rtc_device *rtc, unsigned int enabled) { int err = mutex_lock_interruptible(&rtc->ops_lock); diff --git a/include/linux/rtc.h b/include/linux/rtc.h index 2ca7e8a78060..877ece45426f 100644 --- a/include/linux/rtc.h +++ b/include/linux/rtc.h @@ -228,6 +228,8 @@ extern int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alrm); extern int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alrm); +extern int rtc_initialize_alarm(struct rtc_device *rtc, + struct rtc_wkalrm *alrm); extern void rtc_update_irq(struct rtc_device *rtc, unsigned long num, unsigned long events); -- cgit v1.2.3