3 files changed, 54 insertions, 1 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 19c03ab2bdcb..b377e9672497 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -25,9 +25,17 @@ config RTC_HCTOSYS
           the value read from a specified RTC device. This is useful to avoid
           unnecessary fsck runs at boot time, and to network better.
 
+config RTC_SYSTOHC
+        bool "Set the RTC time based on NTP synchronization"
+        default y
+        help
+          If you say yes here, the system time (wall clock) will be stored
+          in the RTC specified by RTC_HCTOSYS_DEVICE approximately every 11
+          minutes if userspace reports synchronized NTP status.
+
 config RTC_HCTOSYS_DEVICE
         string "RTC used to set the system time"
-        depends on RTC_HCTOSYS = y
+        depends on RTC_HCTOSYS = y || RTC_SYSTOHC = y
         default "rtc0"
         help
           The RTC device that will be used to (re)initialize the system
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 56297f0fd388..69d11f1d76e4 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -6,6 +6,7 @@ ccflags-$(CONFIG_RTC_DEBUG)	:= -DDEBUG
 
 obj-$(CONFIG_RTC_LIB)           += rtc-lib.o
 obj-$(CONFIG_RTC_HCTOSYS)       += hctosys.o
+obj-$(CONFIG_RTC_SYSTOHC)       += systohc.o
 obj-$(CONFIG_RTC_CLASS)         += rtc-core.o
 rtc-core-y                      := class.o interface.o
 
diff --git a/drivers/rtc/systohc.c b/drivers/rtc/systohc.c
new file mode 100644
index 000000000000..bf3e242ccc5c
--- /dev/null
+++ b/drivers/rtc/systohc.c
@@ -0,0 +1,44 @@
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ */
+#include <linux/rtc.h>
+#include <linux/time.h>
+
+/**
+ * rtc_set_ntp_time - Save NTP synchronized time to the RTC
+ * @now: Current time of day
+ *
+ * Replacement for the NTP platform function update_persistent_clock
+ * that stores time for later retrieval by rtc_hctosys.
+ *
+ * Returns 0 on successful RTC update, -ENODEV if a RTC update is not
+ * possible at all, and various other -errno for specific temporary failure
+ * cases.
+ *
+ * If temporary failure is indicated the caller should try again 'soon'
+ */
+int rtc_set_ntp_time(struct timespec now)
+{
+        struct rtc_device *rtc;
+        struct rtc_time tm;
+        int err = -ENODEV;
+
+        if (now.tv_nsec < (NSEC_PER_SEC >> 1))
+                rtc_time_to_tm(now.tv_sec, &tm);
+        else
+                rtc_time_to_tm(now.tv_sec + 1, &tm);
+
+        rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);
+        if (rtc) {
+                /* rtc_hctosys exclusively uses UTC, so we call set_time here,
+                 * not set_mmss. */
+                if (rtc->ops && (rtc->ops->set_time || rtc->ops->set_mmss))
+                        err = rtc_set_time(rtc, &tm);
+                rtc_class_close(rtc);
+        }
+
+        return err;
+}