AT91: add RTT and GPBR based RTC

Signed-off-by: Reinhard Meyer <u-boot@emk-elektronik.de>

arch/arm/include/asm/arch-at91/at91_gpbr.h

+/*
+ * Copyright (C) 2010
+ * Reinhard Meyer, reinhard.meyer@emk-elektronik.de
+ *
+ * General Purpose Backup Registers
+ * Based on AT91SAM9XE datasheet
+ *
+ * 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
+ * (at your option) any later version.
+ */
+
+#ifndef AT91_GPBR_H
+#define AT91_GPBR_H
+
+/*
+ * The Atmel AT91SAM9 series has a small resource of 4 nonvolatile
+ * 32 Bit registers (buffered by the Vbu power).
+ *
+ * Please consider carefully before using this resource for tasks
+ * that do not really need nonvolatile registers. Maybe you can
+ * store information in EEPROM or FLASH instead.
+ *
+ * However, if you use a GPBR please document its use here and
+ * reference the define in your code!
+ *
+ * known typical uses of the GPBRs:
+ * GPBR[0]: offset for RTT timekeeping (u-boot, kernel)
+ * GPBR[1]: unused
+ * GPBR[2]: unused
+ * GPBR[3]: bootcount (u-boot)
+ */
+#define AT91_GPBR_INDEX_TIMEOFF 0
+#define AT91_GPBR_INDEX_BOOTCOUNT 3
+
+#ifndef __ASSEMBLY__
+
+typedef struct at91_gpbr {
+	u32 reg[4];
+} at91_gpbr_t;
+
+#endif /* __ASSEMBLY__ */
+
+#endif

arch/arm/include/asm/arch-at91/at91_rtt.h

+/*
+ * Copyright (C) 2010
+ * Reinhard Meyer, reinhard.meyer@emk-elektronik.de
+ *
+ * Real-time Timer
+ * Based on AT91SAM9XE datasheet
+ *
+ * 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
+ * (at your option) any later version.
+ */
+
+#ifndef AT91_RTT_H
+#define AT91_RTT_H
+
+#ifndef __ASSEMBLY__
+
+typedef struct at91_rtt {
+	u32	mr;	/* Mode Register   RW 0x00008000 */
+	u32	ar;	/* Alarm Register  RW 0xFFFFFFFF */
+	u32	vr;	/* Value Register  RO 0x00000000 */
+	u32	sr;	/* Status Register RO 0x00000000 */
+} at91_rtt_t;
+
+#endif /* __ASSEMBLY__ */
+
+#define AT91_RTT_MR_RTPRES	0x0000ffff
+#define AT91_RTT_MR_ALMIEN	0x00010000
+#define AT91_RTT_RTTINCIEN	0x00020000
+#define AT91_RTT_RTTRST	0x00040000
+
+#define AT91_RTT_SR_ALMS	0x00000001
+#define AT91_RTT_SR_RTTINC	0x00000002
+
+#endif

drivers/rtc/Makefile

@@ -27,6 +27,7 @@ include $(TOPDIR)/config.mk
 
 LIB	= $(obj)librtc.a
 
+COBJS-$(CONFIG_RTC_AT91SAM9_RTT) += at91sam9_rtt.o
 COBJS-$(CONFIG_RTC_BFIN) += bfin_rtc.o
 COBJS-y += date.o
 COBJS-$(CONFIG_RTC_DS12887) += ds12887.o

drivers/rtc/at91sam9_rtt.c

+/*
+ * (C) Copyright 2010
+ * Reinhard Meyer, reinhard.meyer@emk-elektronik.de
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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 (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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+/*
+ * Date & Time support for the internal Real-time Timer
+ * of AT91SAM9260 and compatibles.
+ * Compatible with the LinuX rtc driver workaround:
+ * The RTT cannot be written to, but only reset.
+ * The actual time is the sum of RTT and one of
+ * the four GPBR registers.
+ *
+ * The at91sam9260 has 4 GPBR (0-3).
+ * For their typical use see at91_gpbr.h !
+ *
+ * make sure u-boot and kernel use the same GPBR !
+ */
+
+#include <common.h>
+#include <command.h>
+#include <rtc.h>
+#include <asm/errno.h>
+#include <asm/arch/hardware.h>
+#include <asm/arch/io.h>
+#include <asm/arch/at91_rtt.h>
+#include <asm/arch/at91_gpbr.h>
+
+#if defined(CONFIG_CMD_DATE)
+
+int rtc_get (struct rtc_time *tmp)
+{
+	at91_rtt_t *rtt = (at91_rtt_t *) AT91_RTT_BASE;
+	at91_gpbr_t *gpbr = (at91_gpbr_t *) AT91_GPR_BASE;
+	ulong tim;
+	ulong tim2;
+	ulong off;
+
+	do {
+		tim = readl(&rtt->vr);
+		tim2 = readl(&rtt->vr);
+	} while (tim!=tim2);
+	off = readl(&gpbr->reg[AT91_GPBR_INDEX_TIMEOFF]);
+	/* off==0 means time is invalid, but we ignore that */
+	to_tm (tim+off, tmp);
+	return 0;
+}
+
+int rtc_set (struct rtc_time *tmp)
+{
+	at91_rtt_t *rtt = (at91_rtt_t *) AT91_RTT_BASE;
+	at91_gpbr_t *gpbr = (at91_gpbr_t *) AT91_GPR_BASE;
+	ulong tim;
+
+	tim = mktime (tmp->tm_year, tmp->tm_mon, tmp->tm_mday,
+		      tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
+
+	/* clear alarm, set prescaler to 32768, clear counter */
+	writel(32768+AT91_RTT_RTTRST, &rtt->mr);
+	writel(~0, &rtt->ar);
+	writel(tim, &gpbr->reg[AT91_GPBR_INDEX_TIMEOFF]);
+	/* wait for counter clear to happen, takes less than a 1/32768th second */
+	while (readl(&rtt->vr) != 0)
+		;
+	return 0;
+}
+
+void rtc_reset (void)
+{
+	at91_rtt_t *rtt = (at91_rtt_t *) AT91_RTT_BASE;
+	at91_gpbr_t *gpbr = (at91_gpbr_t *) AT91_GPR_BASE;
+
+	/* clear alarm, set prescaler to 32768, clear counter */
+	writel(32768+AT91_RTT_RTTRST, &rtt->mr);
+	writel(~0, &rtt->ar);
+	writel(0, &gpbr->reg[AT91_GPBR_INDEX_TIMEOFF]);
+	/* wait for counter clear to happen, takes less than a 1/32768th second */
+	while (readl(&rtt->vr) != 0)
+		;
+}
+
+#endif