rtc: suspend()/resume() restores system clock
RTC class suspend/resume support, re-initializing the system clock on resume
from the clock used to initialize it at boot time.
- The reinit-on-resume is hooked to the existing RTC_HCTOSYS config
option, on the grounds that a clock good enough for init must also
be good enough for re-init.
- Inlining a version of the code used by ARM, to save and restore the
delta between a selected RTC and the current system wall-clock time.
- Removes calls to that ARM code from AT91, OMAP1, and S3C RTCs. This
means that systems using those RTCs across suspend/resume will likely
want to change their kernel configs to enable RTC_HCTOSYS.
If HCTOSYS isn't using a second RTC (with battery?), this changes the
system's initial date from Jan 1970 to the epoch this hardware uses:
1998 for AT91, 2000 for OMAP1 (assuming no split power mode), etc.
This goes on top of the patch series removing "struct class_device" usage
from the RTC framework. That's all needed for class suspend()/resume().
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-By: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index d58d74c..587d251 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -32,6 +32,78 @@
kfree(rtc);
}
+#if defined(CONFIG_PM) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
+
+/*
+ * On suspend(), measure the delta between one RTC and the
+ * system's wall clock; restore it on resume().
+ */
+
+static struct timespec delta;
+static time_t oldtime;
+
+static int rtc_suspend(struct device *dev, pm_message_t mesg)
+{
+ struct rtc_device *rtc = to_rtc_device(dev);
+ struct rtc_time tm;
+
+ if (strncmp(rtc->dev.bus_id,
+ CONFIG_RTC_HCTOSYS_DEVICE,
+ BUS_ID_SIZE) != 0)
+ return 0;
+
+ rtc_read_time(rtc, &tm);
+ rtc_tm_to_time(&tm, &oldtime);
+
+ /* RTC precision is 1 second; adjust delta for avg 1/2 sec err */
+ set_normalized_timespec(&delta,
+ xtime.tv_sec - oldtime,
+ xtime.tv_nsec - (NSEC_PER_SEC >> 1));
+
+ return 0;
+}
+
+static int rtc_resume(struct device *dev)
+{
+ struct rtc_device *rtc = to_rtc_device(dev);
+ struct rtc_time tm;
+ time_t newtime;
+ struct timespec time;
+
+ if (strncmp(rtc->dev.bus_id,
+ CONFIG_RTC_HCTOSYS_DEVICE,
+ BUS_ID_SIZE) != 0)
+ return 0;
+
+ rtc_read_time(rtc, &tm);
+ if (rtc_valid_tm(&tm) != 0) {
+ pr_debug("%s: bogus resume time\n", rtc->dev.bus_id);
+ return 0;
+ }
+ rtc_tm_to_time(&tm, &newtime);
+ if (newtime <= oldtime) {
+ if (newtime < oldtime)
+ pr_debug("%s: time travel!\n", rtc->dev.bus_id);
+ return 0;
+ }
+
+ /* restore wall clock using delta against this RTC;
+ * adjust again for avg 1/2 second RTC sampling error
+ */
+ set_normalized_timespec(&time,
+ newtime + delta.tv_sec,
+ (NSEC_PER_SEC >> 1) + delta.tv_nsec);
+ do_settimeofday(&time);
+
+ return 0;
+}
+
+#else
+#define rtc_suspend NULL
+#define rtc_resume NULL
+#endif
+
+
/**
* rtc_device_register - register w/ RTC class
* @dev: the device to register
@@ -143,6 +215,8 @@
printk(KERN_ERR "%s: couldn't create class\n", __FILE__);
return PTR_ERR(rtc_class);
}
+ rtc_class->suspend = rtc_suspend;
+ rtc_class->resume = rtc_resume;
rtc_dev_init();
rtc_sysfs_init(rtc_class);
return 0;