Applied patch set 6 by Ben, derived from Anthony's megapatch, and minor

[pintos-anon] / src / devices / rtc.c

diff --git a/src/devices/rtc.c b/src/devices/rtc.c
new file mode 100644 (file)
index 0000000..d99eb46
--- /dev/null
+++ b/src/devices/rtc.c
@@ -0,0 +1,112 @@
+#include "devices/rtc.h"
+#include <stdio.h>
+#include "threads/io.h"
+
+/* This code is an interface to the MC146818A-compatible real
+   time clock found on PC motherboards.  See [MC146818A] for
+   hardware details. */
+
+/* I/O register addresses. */
+#define CMOS_REG_SET   0x70    /* Selects CMOS register exposed by REG_IO. */
+#define CMOS_REG_IO    0x71    /* Contains the selected data byte. */
+
+/* Indexes of CMOS registers with real-time clock functions.
+   Note that all of these registers are in BCD format,
+   so that 0x59 means 59, not 89. */
+#define RTC_REG_SEC    0       /* Second: 0x00...0x59. */
+#define RTC_REG_MIN    2       /* Minute: 0x00...0x59. */
+#define RTC_REG_HOUR   4       /* Hour: 0x00...0x23. */
+#define RTC_REG_MDAY   7       /* Day of the month: 0x01...0x31. */
+#define RTC_REG_MON    8       /* Month: 0x01...0x12. */
+#define RTC_REG_YEAR   9       /* Year: 0x00...0x99. */
+
+/* Indexes of CMOS control registers. */
+#define RTC_REG_A      0x0a    /* Register A: update-in-progress. */
+#define RTC_REG_B      0x0b    /* Register B: 24/12 hour time, irq enables. */
+#define RTC_REG_C      0x0c    /* Register C: pending interrupts. */
+#define RTC_REG_D      0x0d    /* Register D: valid time? */
+
+/* Register A. */
+#define RTCSA_UIP      0x80    /* Set while time update in progress. */
+
+/* Register B. */
+#define        RTCSB_SET       0x80    /* Disables update to let time be set. */
+#define RTCSB_DM       0x04    /* 0 = BCD time format, 1 = binary format. */
+#define RTCSB_24HR     0x02    /* 0 = 12-hour format, 1 = 24-hour format. */
+
+static int bcd_to_bin (uint8_t);
+static uint8_t cmos_read (uint8_t index);
+
+/* Returns number of seconds since Unix epoch of January 1,
+   1970. */
+time_t
+rtc_get_time (void)
+{
+  static const int days_per_month[12] =
+    {
+      31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
+    };
+  int sec, min, hour, mday, mon, year;
+  time_t time;
+  int i;
+
+  /* Get time components.
+
+     We repeatedly read the time until it is stable from one read
+     to another, in case we start our initial read in the middle
+     of an update.  This strategy is not recommended by the
+     MC146818A datasheet, but it is simpler than any of their
+     suggestions and, furthermore, it is also used by Linux.
+
+     The MC146818A can be configured for BCD or binary format,
+     but for historical reasons everyone always uses BCD format
+     except on obscure non-PC platforms, so we don't bother
+     trying to detect the format in use. */
+  do
+    {
+      sec = bcd_to_bin (cmos_read (RTC_REG_SEC));
+      min = bcd_to_bin (cmos_read (RTC_REG_MIN));
+      hour = bcd_to_bin (cmos_read (RTC_REG_HOUR));
+      mday = bcd_to_bin (cmos_read (RTC_REG_MDAY));
+      mon = bcd_to_bin (cmos_read (RTC_REG_MON));
+      year = bcd_to_bin (cmos_read (RTC_REG_YEAR));
+    }
+  while (sec != bcd_to_bin (cmos_read (RTC_REG_SEC)));
+
+  /* Translate years-since-1900 into years-since-1970.
+     If it's before the epoch, assume that it has passed 2000.
+     This will break at 2070, but that's long after our 31-bit
+     time_t breaks in 2038. */
+  if (year < 70)
+    year += 100;
+  year -= 70;
+
+  /* Break down all components into seconds. */
+  time = (year * 365 + (year - 1) / 4) * 24 * 60 * 60;
+  for (i = 1; i <= mon; i++)
+    time += days_per_month[i - 1] * 24 * 60 * 60;
+  if (mon > 2 && year % 4 == 0)
+    time += 24 * 60 * 60;
+  time += (mday - 1) * 24 * 60 * 60;
+  time += hour * 60 * 60;
+  time += min * 60;
+  time += sec;
+
+  return time;
+}
+
+/* Returns the integer value of the given BCD byte. */
+static int
+bcd_to_bin (uint8_t x)
+{
+  return (x & 0x0f) + ((x >> 4) * 10);
+}
+
+/* Reads a byte from the CMOS register with the given INDEX and
+   returns the byte read. */
+static uint8_t
+cmos_read (uint8_t index)
+{
+  outb (CMOS_REG_SET, index);
+  return inb (CMOS_REG_IO);
+}