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>

1 files changed, 281 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-ab3100.c b/drivers/rtc/rtc-ab3100.c
new file mode 100644
index 000000000000..4704aac2b5af
--- /dev/null
+++ b/drivers/rtc/rtc-ab3100.c
@@ -0,0 +1,281 @@
+/*
+ * 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");