1 files changed, 69 insertions, 0 deletions

diff --git a/drivers/rtc/hctosys.c b/drivers/rtc/hctosys.c
new file mode 100644
index 000000000000..d02fe9a0001f
--- /dev/null
+++ b/drivers/rtc/hctosys.c
@@ -0,0 +1,69 @@
+/*
+ * RTC subsystem, initialize system time on startup
+ *
+ * Copyright (C) 2005 Tower Technologies
+ * Author: Alessandro Zummo <a.zummo@towertech.it>
+ *
+ * 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>
+
+/* IMPORTANT: the RTC only stores whole seconds. It is arbitrary
+ * whether it stores the most close value or the value with partial
+ * seconds truncated. However, it is important that we use it to store
+ * the truncated value. This is because otherwise it is necessary,
+ * in an rtc sync function, to read both xtime.tv_sec and
+ * xtime.tv_nsec. On some processors (i.e. ARM), an atomic read
+ * of >32bits is not possible. So storing the most close value would
+ * slow down the sync API. So here we have the truncated value and
+ * the best guess is to add 0.5s.
+ */
+
+static int __init rtc_hctosys(void)
+{
+        int err;
+        struct rtc_time tm;
+        struct class_device *class_dev = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);
+
+        if (class_dev == NULL) {
+                printk("%s: unable to open rtc device (%s)\n",
+                        __FILE__, CONFIG_RTC_HCTOSYS_DEVICE);
+                return -ENODEV;
+        }
+
+        err = rtc_read_time(class_dev, &tm);
+        if (err == 0) {
+                err = rtc_valid_tm(&tm);
+                if (err == 0) {
+                        struct timespec tv;
+
+                        tv.tv_nsec = NSEC_PER_SEC >> 1;
+
+                        rtc_tm_to_time(&tm, &tv.tv_sec);
+
+                        do_settimeofday(&tv);
+
+                        dev_info(class_dev->dev,
+                                "setting the system clock to "
+                                "%d-%02d-%02d %02d:%02d:%02d (%u)\n",
+                                tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
+                                tm.tm_hour, tm.tm_min, tm.tm_sec,
+                                (unsigned int) tv.tv_sec);
+                }
+                else
+                        dev_err(class_dev->dev,
+                                "hctosys: invalid date/time\n");
+        }
+        else
+                dev_err(class_dev->dev,
+                        "hctosys: unable to read the hardware clock\n");
+
+        rtc_class_close(class_dev);
+
+        return 0;
+}
+
+late_initcall(rtc_hctosys);