--- /dev/null
+#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);
+}
#include "devices/serial.h"
#include "devices/timer.h"
#include "devices/vga.h"
+#include "devices/rtc.h"
#include "threads/interrupt.h"
#include "threads/io.h"
#include "threads/loader.h"
else
PANIC ("unknown option `%s' (use -h for help)", name);
}
+
+ /* Initialize the random number generator based on the system
+ time. This has no effect if an "-rs" option was specified.
+
+ When running under Bochs, this is not enough by itself to
+ get a good seed value, because the pintos script sets the
+ initial time to a predictable value, not to the local time,
+ for reproducibility. To fix this, give the "-r" option to
+ the pintos script to request real-time execution. */
+ random_init (rtc_get_time ());
return argv;
}
projects / pintos-anon / commitdiff