Mon 14 Oct 23:06:38 CEST 2024

kernel/rtc.c

@@ -0,0 +1,196 @@
+/*
+Copyright (C) 2015-2019 The University of Notre Dame
+This software is distributed under the GNU General Public License.
+See the file LICENSE for details.
+*/
+
+/*
+Driver for the Motorola MC 146818A Real Time Clock
+Recommended reading: page 11-15 of the RTC data sheet
+*/
+
+#include "kernel/types.h"
+#include "ioports.h"
+#include "rtc.h"
+#include "console.h"
+#include "string.h"
+#include "interrupt.h"
+
+#define RTC_BASE 0x80
+
+#define RTC_SECONDS        (RTC_BASE+0)
+#define RTC_SECONDS_ALARM  (RTC_BASE+1)
+#define RTC_MINUTES        (RTC_BASE+2)
+#define RTC_MINUTES_ALARM  (RTC_BASE+3)
+#define RTC_HOURS          (RTC_BASE+4)
+#define RTC_HOURS_ALARM    (RTC_BASE+5)
+#define RTC_DAY_OF_WEEK    (RTC_BASE+6)
+#define RTC_DAY_OF_MONTH   (RTC_BASE+7)
+#define RTC_MONTH          (RTC_BASE+8)
+#define RTC_YEAR           (RTC_BASE+9)
+
+#define RTC_REGISTER_A	   (RTC_BASE+10)
+#define RTC_REGISTER_B     (RTC_BASE+11)
+#define RTC_REGISTER_C     (RTC_BASE+12)
+#define RTC_REGISTER_D     (RTC_BASE+13)
+
+#define RTC_ADDRESS_PORT 0x70
+#define RTC_DATA_PORT 0x71
+
+/* Register A bits */
+
+#define RTC_A_UIP (1<<7)
+#define RTC_A_DV2 (1<<6)
+#define RTC_A_DV1 (1<<5)
+#define RTC_A_DV0 (1<<4)
+#define RTC_A_RS3 (1<<3)
+#define RTC_A_RS2 (1<<2)
+#define RTC_A_RS1 (1<<1)
+#define RTC_A_RS0 (1<<0)
+
+/* Register B bits */
+
+#define RTC_B_SET  (1<<7)	/* if set, may write new time */
+#define RTC_B_PIE  (1<<6)	/* periodic interrupt enabled */
+#define RTC_B_AIE  (1<<5)	/* alarm interrupt enabled */
+#define RTC_B_UIE  (1<<4)	/* update interrupt enabled */
+#define RTC_B_SQWE (1<<3)	/* square wave enabled */
+#define RTC_B_DM   (1<<2)	/* data mode: 1=binary 0=decimal */
+#define RTC_B_2412 (1<<1)	/* 1=24 hour mode 0=12 hour mode */
+#define RTC_B_DSE  (1<<0)	/* daylight savings enable */
+
+/* Register C bits */
+/* Note that reading C is necessary to acknowledge an interrupt */
+
+#define RTC_C_IRQF (1<<7)	/* 1=any interrupt pending */
+#define RTC_C_PF   (1<<6)	/* periodic interrupt pending */
+#define RTC_C_AF   (1<<5)	/* alarm interrupt pending */
+#define RTC_C_UF   (1<<4)	/* update interrupt pending */
+
+#define SECS_PER_MIN  60
+#define SECS_PER_HOUR 3600
+#define SECS_PER_DAY  SECS_PER_HOUR * 24
+#define DAYS_PER_WEEK 7
+#define SECS_PER_WEEK SECS_PER_DAY * DAYS_PER_WEEK
+#define SECS_PER_YEAR SECS_PER_WEEK * 52
+
+#define LEAP_YEAR(Y) ( (Y>0) && !(Y%4) && ( (Y%100) || !(Y%400) ) )
+
+uint32_t boottime;
+
+static const uint8_t monthDays[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+
+static uint8_t rtc_bcd_to_binary(uint8_t bcd)
+{
+	return (bcd & 0x0f) + (bcd >> 4) * 10;
+}
+
+static uint8_t rtc_read_port(uint16_t address)
+{
+	outb_slow(address, RTC_ADDRESS_PORT);
+	return inb_slow(RTC_DATA_PORT);
+}
+
+static void rtc_write_port(uint8_t value, uint16_t address)
+{
+	outb_slow(address, RTC_ADDRESS_PORT);
+	outb_slow(value, RTC_DATA_PORT);
+}
+
+static struct rtc_time cached_time;
+
+static void rtc_fetch_time()
+{
+	struct rtc_time t;
+
+	int addpm = 0;
+
+	do {
+		t.second = rtc_read_port(RTC_SECONDS);
+		t.minute = rtc_read_port(RTC_MINUTES);
+		t.hour = rtc_read_port(RTC_HOURS);
+		t.day = rtc_read_port(RTC_DAY_OF_MONTH);
+		t.month = rtc_read_port(RTC_MONTH);
+		t.year = rtc_read_port(RTC_YEAR);
+	} while(t.second != rtc_read_port(RTC_SECONDS));
+
+	if(t.hour & 0x80) {
+		addpm = 1;
+		t.hour &= 0x7f;
+	} else {
+		addpm = 0;
+	}
+
+	t.second = rtc_bcd_to_binary(t.second);
+	t.minute = rtc_bcd_to_binary(t.minute);
+	t.hour = rtc_bcd_to_binary(t.hour);
+	if(addpm)
+		t.hour += 12;
+	t.day = rtc_bcd_to_binary(t.day);
+	t.month = rtc_bcd_to_binary(t.month);
+	t.year = rtc_bcd_to_binary(t.year);
+
+	if(t.year >= 70) {
+		t.year += 1900;
+	} else {
+		t.year += 2000;
+	}
+
+	cached_time = t;
+}
+
+static void rtc_interrupt_handler(int intr, int code)
+{
+	rtc_fetch_time();
+	rtc_read_port(RTC_REGISTER_C);
+}
+
+void rtc_init()
+{
+	uint8_t status;
+
+	status = rtc_read_port(RTC_REGISTER_B);
+	status |= RTC_B_UIE;
+	rtc_write_port(status, RTC_REGISTER_B);
+
+	interrupt_register(40, rtc_interrupt_handler);
+	interrupt_enable(40);
+
+	rtc_fetch_time();
+	struct rtc_time t = {0};
+	rtc_read(&t);
+	boottime = rtc_time_to_timestamp(&t);
+
+	printf("rtc: ready\n");
+}
+
+void rtc_read(struct rtc_time *tout)
+{
+	memcpy(tout, &cached_time, sizeof(cached_time));
+}
+
+uint32_t rtc_time_to_timestamp(struct rtc_time *t)
+{
+	int i;
+	uint32_t seconds;
+
+	seconds = (t->year - 1970) * (SECS_PER_DAY * 365);
+	for(i = 1970; i < t->year; i++) {
+		if(LEAP_YEAR(i)) {
+			seconds += SECS_PER_DAY;
+		}
+	}
+
+	for(i = 1; i < t->month; i++) {
+		if((i == 2) && LEAP_YEAR(t->year)) {
+			seconds += SECS_PER_DAY * 29;
+		} else {
+			seconds += SECS_PER_DAY * monthDays[i - 1];
+		}
+	}
+	seconds += (t->day - 1) * SECS_PER_DAY;
+	seconds += t->hour * SECS_PER_HOUR;
+	seconds += t->minute * SECS_PER_MIN;
+	seconds += t->second;
+	return seconds;
+}