NTP: Add a CONFIG_RTC_SYSTOHC configuration

The purpose of this option is to allow ARM/etc systems that rely on the
class RTC subsystem to have the same kind of automatic NTP based
synchronization that we have on PC platforms. Today ARM does not
implement update_persistent_clock and makes extensive use of the class
RTC system.

When enabled CONFIG_RTC_SYSTOHC will provide a generic
rtc_update_persistent_clock that stores the current time in the RTC and
is intended complement the existing CONFIG_RTC_HCTOSYS option that loads
the RTC at boot.

Like with RTC_HCTOSYS the platform's update_persistent_clock is used
first, if it works. Platforms with mixed class RTC and non-RTC drivers
need to return ENODEV when class RTC should be used. Such an update for
PPC is included in this patch.

Long term, implementations of update_persistent_clock should migrate to
proper class RTC drivers and use CONFIG_RTC_SYSTOHC instead.

Tested on ARM kirkwood and PPC405

Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index ce4cb772dc7833f502e8521fe57ed6eb646c46d5..bc844a857e0597c227d61d87cfc9d4d4ff62c196 100644 (file)
--- 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 19c03ab2bdcb3f2d585c7b38948b5de3bff113c1..b377e9672497b35e550cfefc8fef7edfd2b5eb7c 100644 (file)
--- 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 56297f0fd3884fde9d85cd305cd4b16b439053d2..69d11f1d76e401ad88f0914ccccaba263ce4a7df 100644 (file)
--- 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 (file)
index 0000000..bf3e242
--- /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 9531845c419f8329000b8927a341057bb2a64e6d..11d05f9fe8b6485b43ecaa00395f36919fc13e33 100644 (file)
--- 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 24174b4d669b1280c632d4ed0126dc2f1bb297ef..313b161504b7fab416558193367991aeb06477c6 100644 (file)
--- 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;