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-rw-r--r--drivers/rtc/rtc-cmos.c14
-rw-r--r--drivers/rtc/rtc-dev.c9
-rw-r--r--drivers/rtc/rtc-sysfs.c19
3 files changed, 35 insertions, 7 deletions
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index ab455ddb16c..ff7539a4dbe 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)) {
diff --git a/drivers/rtc/rtc-dev.c b/drivers/rtc/rtc-dev.c
index 025c60a17a4..90dfa0df747 100644
--- a/drivers/rtc/rtc-dev.c
+++ b/drivers/rtc/rtc-dev.c
@@ -246,6 +246,15 @@ static int rtc_dev_ioctl(struct inode *inode, struct file *file,
/* if the driver does not provide the ioctl interface
* or if that particular ioctl was not implemented
* (-ENOIOCTLCMD), we will try to emulate here.
+ *
+ * Drivers *SHOULD NOT* provide ioctl implementations
+ * for these requests. Instead, provide methods to
+ * support the following code, so that the RTC's main
+ * features are accessible without using ioctls.
+ *
+ * RTC and alarm times will be in UTC, by preference,
+ * but dual-booting with MS-Windows implies RTCs must
+ * use the local wall clock time.
*/
switch (cmd) {
diff --git a/drivers/rtc/rtc-sysfs.c b/drivers/rtc/rtc-sysfs.c
index 2ae0e8304d3..4d27ccc4fc0 100644
--- a/drivers/rtc/rtc-sysfs.c
+++ b/drivers/rtc/rtc-sysfs.c
@@ -17,6 +17,13 @@
/* device attributes */
+/*
+ * NOTE: RTC times displayed in sysfs use the RTC's timezone. That's
+ * ideally UTC. However, PCs that also boot to MS-Windows normally use
+ * the local time and change to match daylight savings time. That affects
+ * attributes including date, time, since_epoch, and wakealarm.
+ */
+
static ssize_t
rtc_sysfs_show_name(struct device *dev, struct device_attribute *attr,
char *buf)
@@ -113,13 +120,13 @@ rtc_sysfs_show_wakealarm(struct device *dev, struct device_attribute *attr,
unsigned long alarm;
struct rtc_wkalrm alm;
- /* Don't show disabled alarms; but the RTC could leave the
- * alarm enabled after it's already triggered. Alarms are
- * conceptually one-shot, even though some common hardware
- * (PCs) doesn't actually work that way.
+ /* Don't show disabled alarms. For uniformity, RTC alarms are
+ * conceptually one-shot, even though some common RTCs (on PCs)
+ * don't actually work that way.
*
- * REVISIT maybe we should require RTC implementations to
- * disable the RTC alarm after it triggers, for uniformity.
+ * NOTE: RTC implementations where the alarm doesn't match an
+ * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
+ * alarms after they trigger, to ensure one-shot semantics.
*/
retval = rtc_read_alarm(to_rtc_device(dev), &alm);
if (retval == 0 && alm.enabled) {