at91sam9x: driver to use the internal RTT as RTC

Based on the linux driver.

Signed-off-by Alexander Holler <[email protected]>

---
 README                     |    1 +
 drivers/rtc/Makefile       |    1 +
 drivers/rtc/at91sam9-rtc.c |  162 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 164 insertions(+), 0 deletions(-)
 create mode 100644 drivers/rtc/at91sam9-rtc.c

README +1 -0

index 940b507..afe2aa6 100644
@@ -733,6 +733,7 @@ The following options need to be configured:
 		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
 		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
 		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
+		CONFIG_RTC_AT91SAM9	- use internal RTT of AT91SAM9x
 
 		Note that if the RTC uses I2C, then the I2C interface
 		must also be configured. See I2C Support, below.

drivers/rtc/Makefile +1 -0

index 772a49a..4a48231 100644
@@ -62,6 +62,7 @@ COBJS-$(CONFIG_RTC_RX8025) += rx8025.o
 COBJS-$(CONFIG_RTC_S3C24X0) += s3c24x0_rtc.o
 COBJS-$(CONFIG_RTC_S3C44B0) += s3c44b0_rtc.o
 COBJS-$(CONFIG_RTC_X1205) += x1205.o
+COBJS-$(CONFIG_RTC_AT91SAM9) += at91sam9-rtc.o
 
 COBJS	:= $(sort $(COBJS-y))
 SRCS	:= $(COBJS:.o=.c)

drivers/rtc/at91sam9-rtc.c new file +60 -0

new file mode 100644
index 0000000..d0a263a
@@ -0,0 +1,162 @@
+/*
+ * "RTT as Real Time Clock" driver for AT91SAM9 SoC family
+ *
+ * (C) Copyright 2010
+ * Alexander Holler <[email protected]>
+ *
+ * Based on rtc-at91sam9.c from Michel Benoit
+ * Based on rtc-at91rm9200.c by Rick Bronson
+ *
+ * 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
+ */
+
+/*
+ * This driver uses two configurable hardware resources that live in the
+ * AT91SAM9 backup power domain (intended to be powered at all times)
+ * to implement the Real Time Clock interfaces
+ *
+ *  - A "Real-time Timer" (RTT) counts up in seconds from a base time.
+ *    We can't assign the counter value (CRTV) ... but we can reset it.
+ *
+ *  - One of the "General Purpose Backup Registers" (GPBRs) holds the
+ *    base time, normally an offset from the beginning of the POSIX
+ *    epoch (1970-Jan-1 00:00:00 UTC).  Some systems also include the
+ *    local timezone's offset.
+ *
+ * The RTC's value is the RTT counter plus that offset.  The RTC's alarm
+ * is likewise a base (ALMV) plus that offset.
+ *
+ * Not all RTTs will be used as RTCs; some systems have multiple RTTs to
+ * choose from, or a "real" RTC module.  All systems have multiple GPBR
+ * registers available, likewise usable for more than "RTC" support.
+ *
+ * In addition to CONFIG_CMD_DATE these additional defines must be set:
+ *
+ * #define CONFIG_RTC_AT91SAM9
+ * #define CONFIG_RTC_AT91SAM9_RTT AT91_RTT0_BASE
+ * #define CONFIG_RTC_AT91SAM9_GPBR 0
+ *
+ */
+#include <common.h>
+#include <command.h>
+#include <asm/arch/io.h>
+#include <asm/arch/hardware.h>
+#include <rtc.h>

drivers/rtc/at91sam9-rtc.c new file +36 -0

+
+/* Defines copied from linux/arch/arm/mach-at91/include/mach/at91_rtt.h */
+#define AT91_RTT_MR		0x00		/* Real-time Mode Register */
+#define AT91_RTT_AR		0x04		/* Real-time Alarm Register */
+#define AT91_RTT_VR		0x08		/* Real-time Value Register */
+#define AT91_RTT_RTPRES		(0xffff << 0)	/* Real-time Timer Prescaler Value */
+#define AT91_RTT_ALMIEN		(1 << 16)	/* Alarm Interrupt Enable */
+#define AT91_RTT_RTTINCIEN	(1 << 17)	/* Real Time Timer Increment Interrupt Enable */
+#define AT91_RTT_RTTRST		(1 << 18)	/* Real Time Timer Restart */
+
+/*
+ * We store ALARM_DISABLED in ALMV to record that no alarm is set.
+ * It's also the reset value for that field.
+ */
+#define ALARM_DISABLED	((u32)~0)
+
+#define rtt_readl(field) \
+	readl(CONFIG_RTC_AT91SAM9_RTT + AT91_RTT_ ## field)
+#define rtt_writel(field, val) \
+	writel((val), CONFIG_RTC_AT91SAM9_RTT + AT91_RTT_ ## field)
+#define gpbr_readl() \
+	readl(AT91_GPBR_BASE + 4 * CONFIG_RTC_AT91SAM9_GPBR)
+#define gpbr_writel(val) \
+	writel((val), AT91_GPBR_BASE + 4 * CONFIG_RTC_AT91SAM9_GPBR)
+
+void rtc_reset(void)
+{
+	u32 mr = rtt_readl(MR);
+
+	/* disable interrupts and reset prescaler */
+	mr &= ~(AT91_RTT_RTPRES | AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
+	mr |= AT91_SLOW_CLOCK & AT91_RTT_RTPRES;
+	rtt_writel(MR, mr);
+
+	/* Clear values */
+	gpbr_writel(0);

drivers/rtc/at91sam9-rtc.c new file +23 -0

+	u32 secs, secs2;
+	u32 offset;
+
+	u32 mr = rtt_readl(MR);
+	if ((mr & AT91_RTT_RTPRES) != AT91_SLOW_CLOCK) {
+		printf("Clock not initialized, use date (re)set!\n");
+		return 0;
+	}
+
+	/* read current time offset */
+	offset = gpbr_readl();
+	if (offset == 0) {
+		printf("Time not set!\n");
+		return 0;
+	}
+
+	/* reread the counter to help sync the two clock domains */
+	secs = rtt_readl(VR);
+	secs2 = rtt_readl(VR);
+	if (secs != secs2)
+		secs = rtt_readl(VR);
+
+	to_tm (offset+secs, tmp);

Alexander Holler wrote:

Change parameter name to something more descriptive. 'tmp' implies used locally and this value is passed back. Maybe 'tm' as to_tmp(.., struct rtc_time *tm) ?

Am 03.04.2010 20:33, schrieb Tom:

Quoted 6 lines

Alexander Holler wrote:

Change parameter name to something more descriptive. 'tmp' implies used locally and this value is passed back. Maybe 'tm' as to_tmp(.., struct rtc_time *tm) ?

Maybe someone should place a README in drivers/rtc which reads "Don't use this stuff as template" as almost every source there uses this tmp.

Signed-off-by Alexander Holler <[email protected]>

---
 include/asm-arm/arch-at91/at91sam9260.h |    2 ++
 include/asm-arm/arch-at91/at91sam9261.h |    2 ++
 include/asm-arm/arch-at91/at91sam9263.h |    3 +++
 3 files changed, 7 insertions(+), 0 deletions(-)

Quoted 7 lines · Alexander Holler

Signed-off-by Alexander Holler <[email protected]>

---

include/asm-arm/arch-at91/at91sam9260.h | 2 ++
include/asm-arm/arch-at91/at91sam9261.h | 2 ++
include/asm-arm/arch-at91/at91sam9263.h | 3 +++
3 files changed, 7 insertions(+), 0 deletions(-)

Ack
This change is fine.
Please include this with the changes to the rtc driver in patch 2/2 In general, include all the patches in a patchset when you make a change to any one of them.

Am 03.04.2010 20:36, schrieb Tom:

Quoted 9 lines

Quoted 7 lines · Alexander Holler

Signed-off-by Alexander Holler <[email protected]>

---

include/asm-arm/arch-at91/at91sam9260.h | 2 ++
include/asm-arm/arch-at91/at91sam9261.h | 2 ++
include/asm-arm/arch-at91/at91sam9263.h | 3 +++
3 files changed, 7 insertions(+), 0 deletions(-)

Quoted 5 lines

Ack
This change is fine.
Please include this with the changes to the rtc driver in patch 2/2 In general, include all the patches in a patchset when you make a change to any one of them.

This two patches are unrelated. This patch just makes incomplete headers more complete. If something else would use those two defines and anyone would revert the patch for rtc-driver the revert would eleminate the defines too.