6 files changed, 68 insertions, 6 deletions

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index ce4cb772dc78..bc844a857e05 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -667,7 +667,7 @@ int update_persistent_clock(struct timespec now)
         struct rtc_time tm;
 
         if (!ppc_md.set_rtc_time)
-                return 0;
+                return -ENODEV;
 
         to_tm(now.tv_sec + 1 + timezone_offset, &tm);
         tm.tm_year -= 1900;
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;
+}
diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index 9531845c419f..11d05f9fe8b6 100644
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -138,6 +138,7 @@ extern void rtc_device_unregister(struct rtc_device *rtc);
 extern int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm);
 extern int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm);
 extern int rtc_set_mmss(struct rtc_device *rtc, unsigned long secs);
+extern int rtc_set_ntp_time(struct timespec now);
 int __rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm);
 extern int rtc_read_alarm(struct rtc_device *rtc,
                         struct rtc_wkalrm *alrm);
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 24174b4d669b..313b161504b7 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -15,6 +15,7 @@
 #include <linux/time.h>
 #include <linux/mm.h>
 #include <linux/module.h>
+#include <linux/rtc.h>
 
 #include "tick-internal.h"
 
@@ -483,8 +484,7 @@ out:
         return leap;
 }
 
-#ifdef CONFIG_GENERIC_CMOS_UPDATE
-
+#if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
 static void sync_cmos_clock(struct work_struct *work);
 
 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
@@ -510,14 +510,22 @@ static void sync_cmos_clock(struct work_struct *work)
         }
 
         getnstimeofday(&now);
-        if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
+        if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2) {
+                fail = -ENODEV;
+#ifdef CONFIG_GENERIC_CMOS_UPDATE
                 fail = update_persistent_clock(now);
+#endif
+#ifdef CONFIG_RTC_SYSTOHC
+                if (fail == -ENODEV)
+                        fail = rtc_set_ntp_time(now);
+#endif
+        }
 
         next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
         if (next.tv_nsec <= 0)
                 next.tv_nsec += NSEC_PER_SEC;
 
-        if (!fail)
+        if (!fail || fail == -ENODEV)
                 next.tv_sec = 659;
         else
                 next.tv_sec = 0;