1 files changed, 81 insertions, 0 deletions

diff --git a/arch/sh/boards/mach-dreamcast/rtc.c b/arch/sh/boards/mach-dreamcast/rtc.c
new file mode 100644
index 000000000000..a7433685798d
--- /dev/null
+++ b/arch/sh/boards/mach-dreamcast/rtc.c
@@ -0,0 +1,81 @@
+/*
+ * arch/sh/boards/dreamcast/rtc.c
+ *
+ * Dreamcast AICA RTC routines.
+ *
+ * Copyright (c) 2001, 2002 M. R. Brown <mrbrown@0xd6.org>
+ * Copyright (c) 2002 Paul Mundt <lethal@chaoticdreams.org>
+ *
+ * Released under the terms of the GNU GPL v2.0.
+ *
+ */
+
+#include <linux/time.h>
+#include <asm/rtc.h>
+#include <asm/io.h>
+
+/* The AICA RTC has an Epoch of 1/1/1950, so we must subtract 20 years (in
+   seconds) to get the standard Unix Epoch when getting the time, and add
+   20 years when setting the time. */
+#define TWENTY_YEARS ((20 * 365LU + 5) * 86400)
+
+/* The AICA RTC is represented by a 32-bit seconds counter stored in 2 16-bit
+   registers.*/
+#define AICA_RTC_SECS_H         0xa0710000
+#define AICA_RTC_SECS_L         0xa0710004
+
+/**
+ * aica_rtc_gettimeofday - Get the time from the AICA RTC
+ * @ts: pointer to resulting timespec
+ *
+ * Grabs the current RTC seconds counter and adjusts it to the Unix Epoch.
+ */
+static void aica_rtc_gettimeofday(struct timespec *ts)
+{
+        unsigned long val1, val2;
+
+        do {
+                val1 = ((ctrl_inl(AICA_RTC_SECS_H) & 0xffff) << 16) |
+                        (ctrl_inl(AICA_RTC_SECS_L) & 0xffff);
+
+                val2 = ((ctrl_inl(AICA_RTC_SECS_H) & 0xffff) << 16) |
+                        (ctrl_inl(AICA_RTC_SECS_L) & 0xffff);
+        } while (val1 != val2);
+
+        ts->tv_sec = val1 - TWENTY_YEARS;
+
+        /* Can't get nanoseconds with just a seconds counter. */
+        ts->tv_nsec = 0;
+}
+
+/**
+ * aica_rtc_settimeofday - Set the AICA RTC to the current time
+ * @secs: contains the time_t to set
+ *
+ * Adjusts the given @tv to the AICA Epoch and sets the RTC seconds counter.
+ */
+static int aica_rtc_settimeofday(const time_t secs)
+{
+        unsigned long val1, val2;
+        unsigned long adj = secs + TWENTY_YEARS;
+
+        do {
+                ctrl_outl((adj & 0xffff0000) >> 16, AICA_RTC_SECS_H);
+                ctrl_outl((adj & 0xffff), AICA_RTC_SECS_L);
+
+                val1 = ((ctrl_inl(AICA_RTC_SECS_H) & 0xffff) << 16) |
+                        (ctrl_inl(AICA_RTC_SECS_L) & 0xffff);
+
+                val2 = ((ctrl_inl(AICA_RTC_SECS_H) & 0xffff) << 16) |
+                        (ctrl_inl(AICA_RTC_SECS_L) & 0xffff);
+        } while (val1 != val2);
+
+        return 0;
+}
+
+void aica_time_init(void)
+{
+        rtc_sh_get_time = aica_rtc_gettimeofday;
+        rtc_sh_set_time = aica_rtc_settimeofday;
+}
+