rtc: AB3100 RTC support

This adds support for the RTC found inside the AB3100 Mixed Signal chip.
The symbols used for communicating with the chip is found in the
mfd/ab3100-core.c driver that also provides the platform device.
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Acked-by: Alessandro Zummo <alessandro.zummo@towertech.it>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/rtc/Kconfig

@@ -545,6 +545,15 @@ config RTC_DRV_PCF50633
 	  If you say yes here you get support for the RTC subsystem of the
 	  NXP PCF50633 used in embedded systems.
 
+config RTC_DRV_AB3100
+	tristate "ST-Ericsson AB3100 RTC"
+	depends on AB3100_CORE
+	default y if AB3100_CORE
+	help
+	  Select this to enable the ST-Ericsson AB3100 Mixed Signal IC RTC
+	  support. This chip contains a battery- and capacitor-backed RTC.
+
+
 comment "on-CPU RTC drivers"
 
 config RTC_DRV_OMAP

drivers/rtc/Makefile

@@ -17,6 +17,7 @@ rtc-core-$(CONFIG_RTC_INTF_SYSFS) += rtc-sysfs.o
 
 # Keep the list ordered.
 
+obj-$(CONFIG_RTC_DRV_AB3100)	+= rtc-ab3100.o
 obj-$(CONFIG_RTC_DRV_AT32AP700X)+= rtc-at32ap700x.o
 obj-$(CONFIG_RTC_DRV_AT91RM9200)+= rtc-at91rm9200.o
 obj-$(CONFIG_RTC_DRV_AT91SAM9)	+= rtc-at91sam9.o

drivers/rtc/rtc-ab3100.c

+/*
+ * Copyright (C) 2007-2009 ST-Ericsson AB
+ * License terms: GNU General Public License (GPL) version 2
+ * RTC clock driver for the AB3100 Analog Baseband Chip
+ * Author: Linus Walleij <linus.walleij@stericsson.com>
+ */
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/mfd/ab3100.h>
+
+/* Clock rate in Hz */
+#define AB3100_RTC_CLOCK_RATE	32768
+
+/*
+ * The AB3100 RTC registers. These are the same for
+ * AB3000 and AB3100.
+ * Control register:
+ * Bit 0: RTC Monitor cleared=0, active=1, if you set it
+ *        to 1 it remains active until RTC power is lost.
+ * Bit 1: 32 kHz Oscillator, 0 = on, 1 = bypass
+ * Bit 2: Alarm on, 0 = off, 1 = on
+ * Bit 3: 32 kHz buffer disabling, 0 = enabled, 1 = disabled
+ */
+#define AB3100_RTC		0x53
+/* default setting, buffer disabled, alarm on */
+#define RTC_SETTING		0x30
+/* Alarm when AL0-AL3 == TI0-TI3  */
+#define AB3100_AL0		0x56
+#define AB3100_AL1		0x57
+#define AB3100_AL2		0x58
+#define AB3100_AL3		0x59
+/* This 48-bit register that counts up at 32768 Hz */
+#define AB3100_TI0		0x5a
+#define AB3100_TI1		0x5b
+#define AB3100_TI2		0x5c
+#define AB3100_TI3		0x5d
+#define AB3100_TI4		0x5e
+#define AB3100_TI5		0x5f
+
+/*
+ * RTC clock functions and device struct declaration
+ */
+static int ab3100_rtc_set_mmss(struct device *dev, unsigned long secs)
+{
+	struct ab3100 *ab3100_data = dev_get_drvdata(dev);
+	u8 regs[] = {AB3100_TI0, AB3100_TI1, AB3100_TI2,
+		     AB3100_TI3, AB3100_TI4, AB3100_TI5};
+	unsigned char buf[6];
+	u64 fat_time = (u64) secs * AB3100_RTC_CLOCK_RATE * 2;
+	int err = 0;
+	int i;
+
+	buf[0] = (fat_time) & 0xFF;
+	buf[1] = (fat_time >> 8) & 0xFF;
+	buf[2] = (fat_time >> 16) & 0xFF;
+	buf[3] = (fat_time >> 24) & 0xFF;
+	buf[4] = (fat_time >> 32) & 0xFF;
+	buf[5] = (fat_time >> 40) & 0xFF;
+
+	for (i = 0; i < 6; i++) {
+		err = ab3100_set_register_interruptible(ab3100_data,
+							regs[i], buf[i]);
+		if (err)
+			return err;
+	}
+
+	/* Set the flag to mark that the clock is now set */
+	return ab3100_mask_and_set_register_interruptible(ab3100_data,
+							  AB3100_RTC,
+							  0xFE, 0x01);
+
+}
+
+static int ab3100_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct ab3100 *ab3100_data = dev_get_drvdata(dev);
+	unsigned long time;
+	u8 rtcval;
+	int err;
+
+	err = ab3100_get_register_interruptible(ab3100_data,
+						AB3100_RTC, &rtcval);
+	if (err)
+		return err;
+
+	if (!(rtcval & 0x01)) {
+		dev_info(dev, "clock not set (lost power)");
+		return -EINVAL;
+	} else {
+		u64 fat_time;
+		u8 buf[6];
+
+		/* Read out time registers */
+		err = ab3100_get_register_page_interruptible(ab3100_data,
+							     AB3100_TI0,
+							     buf, 6);
+		if (err != 0)
+			return err;
+
+		fat_time = ((u64) buf[5] << 40) | ((u64) buf[4] << 32) |
+			((u64) buf[3] << 24) | ((u64) buf[2] << 16) |
+			((u64) buf[1] << 8) | (u64) buf[0];
+		time = (unsigned long) (fat_time /
+					(u64) (AB3100_RTC_CLOCK_RATE * 2));
+	}
+
+	rtc_time_to_tm(time, tm);
+
+	return rtc_valid_tm(tm);
+}
+
+static int ab3100_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct ab3100 *ab3100_data = dev_get_drvdata(dev);
+	unsigned long time;
+	u64 fat_time;
+	u8 buf[6];
+	u8 rtcval;
+	int err;
+
+	/* Figure out if alarm is enabled or not */
+	err = ab3100_get_register_interruptible(ab3100_data,
+						AB3100_RTC, &rtcval);
+	if (err)
+		return err;
+	if (rtcval & 0x04)
+		alarm->enabled = 1;
+	else
+		alarm->enabled = 0;
+	/* No idea how this could be represented */
+	alarm->pending = 0;
+	/* Read out alarm registers, only 4 bytes */
+	err = ab3100_get_register_page_interruptible(ab3100_data,
+						     AB3100_AL0, buf, 4);
+	if (err)
+		return err;
+	fat_time = ((u64) buf[3] << 40) | ((u64) buf[2] << 32) |
+		((u64) buf[1] << 24) | ((u64) buf[0] << 16);
+	time = (unsigned long) (fat_time / (u64) (AB3100_RTC_CLOCK_RATE * 2));
+
+	rtc_time_to_tm(time, &alarm->time);
+
+	return rtc_valid_tm(&alarm->time);
+}
+
+static int ab3100_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct ab3100 *ab3100_data = dev_get_drvdata(dev);
+	u8 regs[] = {AB3100_AL0, AB3100_AL1, AB3100_AL2, AB3100_AL3};
+	unsigned char buf[4];
+	unsigned long secs;
+	u64 fat_time;
+	int err;
+	int i;
+
+	rtc_tm_to_time(&alarm->time, &secs);
+	fat_time = (u64) secs * AB3100_RTC_CLOCK_RATE * 2;
+	buf[0] = (fat_time >> 16) & 0xFF;
+	buf[1] = (fat_time >> 24) & 0xFF;
+	buf[2] = (fat_time >> 32) & 0xFF;
+	buf[3] = (fat_time >> 40) & 0xFF;
+
+	/* Set the alarm */
+	for (i = 0; i < 4; i++) {
+		err = ab3100_set_register_interruptible(ab3100_data,
+							regs[i], buf[i]);
+		if (err)
+			return err;
+	}
+	/* Then enable the alarm */
+	return ab3100_mask_and_set_register_interruptible(ab3100_data,
+							  AB3100_RTC, ~(1 << 2),
+							  alarm->enabled << 2);
+}
+
+static int ab3100_rtc_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct ab3100 *ab3100_data = dev_get_drvdata(dev);
+
+	/*
+	 * It's not possible to enable/disable the alarm IRQ for this RTC.
+	 * It does not actually trigger any IRQ: instead its only function is
+	 * to power up the system, if it wasn't on. This will manifest as
+	 * a "power up cause" in the AB3100 power driver (battery charging etc)
+	 * and need to be handled there instead.
+	 */
+	if (enabled)
+		return ab3100_mask_and_set_register_interruptible(ab3100_data,
+						    AB3100_RTC, ~(1 << 2),
+						    1 << 2);
+	else
+		return ab3100_mask_and_set_register_interruptible(ab3100_data,
+						    AB3100_RTC, ~(1 << 2),
+						    0);
+}
+
+static const struct rtc_class_ops ab3100_rtc_ops = {
+	.read_time	= ab3100_rtc_read_time,
+	.set_mmss	= ab3100_rtc_set_mmss,
+	.read_alarm	= ab3100_rtc_read_alarm,
+	.set_alarm	= ab3100_rtc_set_alarm,
+	.alarm_irq_enable = ab3100_rtc_irq_enable,
+};
+
+static int __init ab3100_rtc_probe(struct platform_device *pdev)
+{
+	int err;
+	u8 regval;
+	struct rtc_device *rtc;
+	struct ab3100 *ab3100_data = platform_get_drvdata(pdev);
+
+	/* The first RTC register needs special treatment */
+	err = ab3100_get_register_interruptible(ab3100_data,
+						AB3100_RTC, &regval);
+	if (err) {
+		dev_err(&pdev->dev, "unable to read RTC register\n");
+		return -ENODEV;
+	}
+
+	if ((regval & 0xFE) != RTC_SETTING) {
+		dev_warn(&pdev->dev, "not default value in RTC reg 0x%x\n",
+			 regval);
+	}
+
+	if ((regval & 1) == 0) {
+		/*
+		 * Set bit to detect power loss.
+		 * This bit remains until RTC power is lost.
+		 */
+		regval = 1 | RTC_SETTING;
+		err = ab3100_set_register_interruptible(ab3100_data,
+							AB3100_RTC, regval);
+		/* Ignore any error on this write */
+	}
+
+	rtc = rtc_device_register("ab3100-rtc", &pdev->dev, &ab3100_rtc_ops,
+				  THIS_MODULE);
+	if (IS_ERR(rtc)) {
+		err = PTR_ERR(rtc);
+		return err;
+	}
+
+	return 0;
+}
+
+static int __exit ab3100_rtc_remove(struct platform_device *pdev)
+{
+	struct rtc_device *rtc = platform_get_drvdata(pdev);
+
+	rtc_device_unregister(rtc);
+	return 0;
+}
+
+static struct platform_driver ab3100_rtc_driver = {
+	.driver = {
+		.name = "ab3100-rtc",
+		.owner = THIS_MODULE,
+	},
+	.remove	 = __exit_p(ab3100_rtc_remove),
+};
+
+static int __init ab3100_rtc_init(void)
+{
+	return platform_driver_probe(&ab3100_rtc_driver,
+				     ab3100_rtc_probe);
+}
+
+static void __exit ab3100_rtc_exit(void)
+{
+	platform_driver_unregister(&ab3100_rtc_driver);
+}
+
+module_init(ab3100_rtc_init);
+module_exit(ab3100_rtc_exit);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@stericsson.com>");
+MODULE_DESCRIPTION("AB3100 RTC Driver");
+MODULE_LICENSE("GPL");