[time] Add RTC-based time source

Add a time source using the CMOS RTC to obtain the current time.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/include/bits/time.h

@@ -9,4 +9,6 @@
 
 FILE_LICENCE ( GPL2_OR_LATER );
 
+#include <ipxe/rtc_time.h>
+
 #endif /* _BITS_TIME_H */

src/arch/i386/include/ipxe/rtc_time.h

@@ -0,0 +1,18 @@
+#ifndef _IPXE_RTC_TIME_H
+#define _IPXE_RTC_TIME_H
+
+/** @file
+ *
+ * RTC-based time source
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#ifdef TIME_RTC
+#define TIME_PREFIX_rtc
+#else
+#define TIME_PREFIX_rtc __rtc_
+#endif
+
+#endif /* _IPXE_RTC_TIME_H */

src/arch/i386/include/rtc.h

@@ -0,0 +1,83 @@
+#ifndef _RTC_H
+#define _RTC_H
+
+/** @file
+ *
+ * CMOS Real-Time Clock (RTC)
+ *
+ * The CMOS/RTC registers are documented (with varying degrees of
+ * accuracy and consistency) at
+ *
+ *    http://www.nondot.org/sabre/os/files/MiscHW/RealtimeClockFAQ.txt
+ *    http://wiki.osdev.org/RTC
+ *    http://wiki.osdev.org/CMOS
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <pic8259.h>
+
+/** RTC IRQ */
+#define RTC_IRQ 8
+
+/** RTC interrupt vector */
+#define RTC_INT IRQ_INT ( RTC_IRQ )
+
+/** CMOS/RTC address (and NMI) register */
+#define CMOS_ADDRESS 0x70
+
+/** NMI disable bit */
+#define CMOS_DISABLE_NMI 0x80
+
+/** CMOS/RTC data register */
+#define CMOS_DATA 0x71
+
+/** RTC seconds */
+#define RTC_SEC 0x00
+
+/** RTC minutes */
+#define RTC_MIN 0x02
+
+/** RTC hours */
+#define RTC_HOUR 0x04
+
+/** RTC weekday */
+#define RTC_WDAY 0x06
+
+/** RTC day of month */
+#define RTC_MDAY 0x07
+
+/** RTC month */
+#define RTC_MON 0x08
+
+/** RTC year */
+#define RTC_YEAR 0x09
+
+/** RTC status register A */
+#define RTC_STATUS_A 0x0a
+
+/** RTC update in progress bit */
+#define RTC_STATUS_A_UPDATE_IN_PROGRESS 0x80
+
+/** RTC status register B */
+#define RTC_STATUS_B 0x0b
+
+/** RTC 24 hour format bit */
+#define RTC_STATUS_B_24_HOUR 0x02
+
+/** RTC binary mode bit */
+#define RTC_STATUS_B_BINARY 0x04
+
+/** RTC Periodic Interrupt Enabled bit */
+#define RTC_STATUS_B_PIE 0x40
+
+/** RTC status register C */
+#define RTC_STATUS_C 0x0c
+
+/** RTC status register D */
+#define RTC_STATUS_D 0x0d
+
+/** CMOS default address */
+#define CMOS_DEFAULT_ADDRESS RTC_STATUS_D
+
+#endif /* _RTC_H */

src/arch/i386/interface/pcbios/rtc_entropy.c

@@ -22,53 +22,15 @@ FILE_LICENCE ( GPL2_OR_LATER );
  *
  * RTC-based entropy source
  *
- * The CMOS/RTC registers are documented (with varying degrees of
- * accuracy and consistency) at
- *
- *    http://www.nondot.org/sabre/os/files/MiscHW/RealtimeClockFAQ.txt
- *    http://wiki.osdev.org/RTC
- *    http://wiki.osdev.org/CMOS
  */
 
 #include <stdint.h>
 #include <string.h>
 #include <biosint.h>
 #include <pic8259.h>
+#include <rtc.h>
 #include <ipxe/entropy.h>
 
-/** RTC IRQ */
-#define RTC_IRQ 8
-
-/** RTC interrupt vector */
-#define RTC_INT IRQ_INT ( RTC_IRQ )
-
-/** CMOS/RTC address (and NMI) register */
-#define CMOS_ADDRESS 0x70
-
-/** NMI disable bit */
-#define CMOS_DISABLE_NMI 0x80
-
-/** CMOS/RTC data register */
-#define CMOS_DATA 0x71
-
-/** RTC status register A */
-#define RTC_STATUS_A 0x0a
-
-/** RTC status register B */
-#define RTC_STATUS_B 0x0b
-
-/** RTC Periodic Interrupt Enabled bit */
-#define RTC_STATUS_B_PIE 0x40
-
-/** RTC status register C */
-#define RTC_STATUS_C 0x0c
-
-/** RTC status register D */
-#define RTC_STATUS_D 0x0d
-
-/** CMOS default address */
-#define CMOS_DEFAULT_ADDRESS RTC_STATUS_D
-
 /** RTC "interrupt triggered" flag */
 static uint8_t __text16 ( rtc_flag );
 #define rtc_flag __use_text16 ( rtc_flag )

src/arch/i386/interface/pcbios/rtc_time.c

@@ -0,0 +1,137 @@
+/*
+ * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * 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 2 of the
+ * License, or 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, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/** @file
+ *
+ * RTC-based time source
+ *
+ */
+
+#include <stdint.h>
+#include <time.h>
+#include <rtc.h>
+#include <ipxe/time.h>
+
+/**
+ * Read RTC register
+ *
+ * @v address		Register address
+ * @ret data		Data
+ */
+static unsigned int rtc_readb ( int address ) {
+	outb ( address, CMOS_ADDRESS );
+	return inb ( CMOS_DATA );
+}
+
+/**
+ * Check if RTC update is in progress
+ *
+ * @ret is_busy		RTC update is in progress
+ */
+static int rtc_is_busy ( void ) {
+	return ( rtc_readb ( RTC_STATUS_A ) & RTC_STATUS_A_UPDATE_IN_PROGRESS );
+}
+
+/**
+ * Read RTC BCD register
+ *
+ * @v address		Register address
+ * @ret value		Value
+ */
+static unsigned int rtc_readb_bcd ( int address ) {
+	unsigned int bcd;
+
+	bcd = rtc_readb ( address );
+	return ( bcd - ( 6 * ( bcd >> 4 ) ) );
+}
+
+/**
+ * Read RTC time
+ *
+ * @ret time		Time, in seconds
+ */
+static time_t rtc_read_time ( void ) {
+	unsigned int status_b;
+	int is_binary;
+	int is_24hour;
+	unsigned int ( * read_component ) ( int address );
+	struct tm tm;
+	int is_pm;
+	unsigned int hour;
+	time_t time;
+
+	/* Wait for any in-progress update to complete */
+	while ( rtc_is_busy() ) {}
+
+	/* Determine RTC mode */
+	status_b = rtc_readb ( RTC_STATUS_B );
+	is_binary = ( status_b & RTC_STATUS_B_BINARY );
+	is_24hour = ( status_b & RTC_STATUS_B_24_HOUR );
+	read_component = ( is_binary ? rtc_readb : rtc_readb_bcd );
+
+	/* Read time values */
+	tm.tm_sec = read_component ( RTC_SEC );
+	tm.tm_min = read_component ( RTC_MIN );
+	hour = read_component ( RTC_HOUR );
+	if ( ! is_24hour ) {
+		is_pm = ( hour >= 80 );
+		hour = ( ( ( ( hour & 0x7f ) % 80 ) % 12 ) +
+			 ( is_pm ? 12 : 0 ) );
+	}
+	tm.tm_hour = hour;
+	tm.tm_mday = read_component ( RTC_MDAY );
+	tm.tm_mon = ( read_component ( RTC_MON ) - 1 );
+	tm.tm_year = ( read_component ( RTC_YEAR ) +
+		       100 /* Assume we are in the 21st century, since
+			    * this code was written in 2012 */ );
+
+	DBGC ( RTC_STATUS_A, "RTCTIME is %04d-%02d-%02d %02d:%02d:%02d "
+	       "(%s,%d-hour)\n", ( tm.tm_year + 1900 ), ( tm.tm_mon + 1 ),
+	       tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec,
+	       ( is_binary ? "binary" : "BCD" ), ( is_24hour ? 24 : 12 ) );
+
+	/* Convert to seconds since the Epoch */
+	time = mktime ( &tm );
+
+	return time;
+}
+
+/**
+ * Get current time in seconds
+ *
+ * @ret time		Time, in seconds
+ */
+static time_t rtc_now ( void ) {
+	time_t time = 0;
+	time_t last_time;
+
+	/* Read time until we get two matching values in a row, in
+	 * case we end up reading a corrupted value in the middle of
+	 * an update.
+	 */
+	do {
+		last_time = time;
+		time = rtc_read_time();
+	} while ( time != last_time );
+
+	return time;
+}
+
+PROVIDE_TIME ( rtc, time_now, rtc_now );

src/config/defaults/pcbios.h

@@ -19,7 +19,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define SMBIOS_PCBIOS
 #define SANBOOT_PCBIOS
 #define ENTROPY_RTC
-#define TIME_NULL
+#define TIME_RTC
 
 #define	IMAGE_ELF		/* ELF image support */
 #define	IMAGE_MULTIBOOT		/* MultiBoot image support */