X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=bootcensus;a=blobdiff_plain;f=src%2Frtc.c;fp=src%2Frtc.c;h=40eca9adfe5640a16d0b3070a72f9a6a5a316352;hp=0000000000000000000000000000000000000000;hb=78e3e75fc7b5838d0261c876d00e1b8c3e0bcfe0;hpb=7b6f6de2124e28ae7da5599a7cdaf2c171c4f15e

diff --git a/src/rtc.c b/src/rtc.c
new file mode 100644
index 0000000..40eca9a
--- /dev/null
+++ b/src/rtc.c
@@ -0,0 +1,123 @@
+/*
+pcboot - bootable PC demo/game kernel
+Copyright (C) 2018-2019  John Tsiombikas <nuclear@member.fsf.org>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY, without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+#include <stdio.h>
+#include <time.h>
+#include <asmops.h>
+#include "rtc.h"
+
+/* CMOS I/O ports */
+#define PORT_CTL	0x70
+#define PORT_DATA	0x71
+
+/* CMOS RTC registers */
+#define REG_SEC			0
+#define REG_ALARM_SEC	1
+#define REG_MIN			2
+#define REG_ALARM_MIN	3
+#define REG_HOUR		4
+#define REG_ALARM_HOUR	5
+#define REG_WEEKDAY		6
+#define REG_DAY			7
+#define REG_MONTH		8
+#define REG_YEAR		9
+#define REG_STATA		10
+#define REG_STATB		11
+#define REG_STATC		12
+#define REG_STATD		13
+
+#define STATA_BUSY	(1 << 7)
+#define STATB_24HR	(1 << 1)
+#define STATB_BIN	(1 << 2)
+
+#define HOUR_PM_BIT		(1 << 7)
+
+#define BCD_TO_BIN(x)	((((x) >> 4) & 0xf) * 10 + ((x) & 0xf))
+
+static void read_rtc(struct tm *tm);
+static int read_reg(int reg);
+
+
+void init_rtc(void)
+{
+	struct tm tm;
+
+	read_rtc(&tm);
+	start_time = mktime(&tm);
+
+	printf("System real-time clock: %s", asctime(&tm));
+}
+
+
+static void read_rtc(struct tm *tm)
+{
+	int statb, pm;
+
+	/* wait for any clock updates to finish */
+	while(read_reg(REG_STATA) & STATA_BUSY);
+
+	tm->tm_sec = read_reg(REG_SEC);
+	tm->tm_min = read_reg(REG_MIN);
+	tm->tm_hour = read_reg(REG_HOUR);
+	tm->tm_mday = read_reg(REG_DAY);
+	tm->tm_mon = read_reg(REG_MONTH);
+	tm->tm_year = read_reg(REG_YEAR);
+
+	/* in 12hour mode, bit 7 means post-meridiem */
+	pm = tm->tm_hour & HOUR_PM_BIT;
+	tm->tm_hour &= ~HOUR_PM_BIT;
+
+	/* convert to binary if needed */
+	statb = read_reg(REG_STATB);
+	if(!(statb & STATB_BIN)) {
+		tm->tm_sec = BCD_TO_BIN(tm->tm_sec);
+		tm->tm_min = BCD_TO_BIN(tm->tm_min);
+		tm->tm_hour = BCD_TO_BIN(tm->tm_hour);
+		tm->tm_mday = BCD_TO_BIN(tm->tm_mday);
+		tm->tm_mon = BCD_TO_BIN(tm->tm_mon);
+		tm->tm_year = BCD_TO_BIN(tm->tm_year);
+	}
+
+	/* make the year an offset from 1900 */
+	if(tm->tm_year < 100) {
+		tm->tm_year += 100;
+	} else {
+		tm->tm_year -= 1900;
+	}
+
+	/* if tm_hour is in 12h mode, convert to 24h */
+	if(!(statb & STATB_24HR)) {
+		if(tm->tm_hour == 12) {
+			tm->tm_hour = 0;
+		}
+		if(pm) {
+			tm->tm_hour += 12;
+		}
+	}
+
+	tm->tm_mon -= 1;	/* we want months to start from 0 */
+}
+
+static int read_reg(int reg)
+{
+	unsigned char val;
+	outb(reg, PORT_CTL);
+	iodelay();
+	val = inb(PORT_DATA);
+	iodelay();
+	return val;
+}