rtc: sc27xx: Add Spreadtrum SC27xx PMIC RTC driver

This patch adds the Spreadtrum RTC driver, which embedded in the
Spreadtrum SC27xx series PMICs.

Signed-off-by: Baolin Wang <baolin.wang@spreadtrum.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

3 files changed, 674 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 47663e03f9a8..b59a31b079a5 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1187,6 +1187,17 @@ config RTC_DRV_WM8350
           This driver can also be built as a module. If so, the module
           will be called "rtc-wm8350".
 
+config RTC_DRV_SC27XX
+        tristate "Spreadtrum SC27xx RTC"
+        depends on MFD_SC27XX_PMIC || COMPILE_TEST
+        help
+          If you say Y here you will get support for the RTC subsystem
+          of the Spreadtrum SC27xx series PMICs. The SC27xx series PMICs
+          includes the SC2720, SC2721, SC2723, SC2730 and SC2731 chips.
+
+          This driver can also be built as a module. If so, the module
+          will be called rtc-sc27xx.
+
 config RTC_DRV_SPEAR
         tristate "SPEAR ST RTC"
         depends on PLAT_SPEAR || COMPILE_TEST
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 0b5acd6b5cc3..5cf6b0a44f01 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -145,6 +145,7 @@ obj-$(CONFIG_RTC_DRV_S35390A)	+= rtc-s35390a.o
 obj-$(CONFIG_RTC_DRV_S3C)       += rtc-s3c.o
 obj-$(CONFIG_RTC_DRV_S5M)       += rtc-s5m.o
 obj-$(CONFIG_RTC_DRV_SA1100)    += rtc-sa1100.o
+obj-$(CONFIG_RTC_DRV_SC27XX)    += rtc-sc27xx.o
 obj-$(CONFIG_RTC_DRV_SH)        += rtc-sh.o
 obj-$(CONFIG_RTC_DRV_SIRFSOC)   += rtc-sirfsoc.o
 obj-$(CONFIG_RTC_DRV_SNVS)      += rtc-snvs.o
diff --git a/drivers/rtc/rtc-sc27xx.c b/drivers/rtc/rtc-sc27xx.c
new file mode 100644
index 000000000000..d544d5268757
--- /dev/null
+++ b/drivers/rtc/rtc-sc27xx.c
@@ -0,0 +1,662 @@
+/*
+ * Copyright (C) 2017 Spreadtrum Communications Inc.
+ *
+ * SPDX-License-Identifier: GPL-2.0
+ */
+
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+
+#define SPRD_RTC_SEC_CNT_VALUE          0x0
+#define SPRD_RTC_MIN_CNT_VALUE          0x4
+#define SPRD_RTC_HOUR_CNT_VALUE         0x8
+#define SPRD_RTC_DAY_CNT_VALUE          0xc
+#define SPRD_RTC_SEC_CNT_UPD            0x10
+#define SPRD_RTC_MIN_CNT_UPD            0x14
+#define SPRD_RTC_HOUR_CNT_UPD           0x18
+#define SPRD_RTC_DAY_CNT_UPD            0x1c
+#define SPRD_RTC_SEC_ALM_UPD            0x20
+#define SPRD_RTC_MIN_ALM_UPD            0x24
+#define SPRD_RTC_HOUR_ALM_UPD           0x28
+#define SPRD_RTC_DAY_ALM_UPD            0x2c
+#define SPRD_RTC_INT_EN                 0x30
+#define SPRD_RTC_INT_RAW_STS            0x34
+#define SPRD_RTC_INT_CLR                0x38
+#define SPRD_RTC_INT_MASK_STS           0x3C
+#define SPRD_RTC_SEC_ALM_VALUE          0x40
+#define SPRD_RTC_MIN_ALM_VALUE          0x44
+#define SPRD_RTC_HOUR_ALM_VALUE         0x48
+#define SPRD_RTC_DAY_ALM_VALUE          0x4c
+#define SPRD_RTC_SPG_VALUE              0x50
+#define SPRD_RTC_SPG_UPD                0x54
+#define SPRD_RTC_SEC_AUXALM_UPD         0x60
+#define SPRD_RTC_MIN_AUXALM_UPD         0x64
+#define SPRD_RTC_HOUR_AUXALM_UPD        0x68
+#define SPRD_RTC_DAY_AUXALM_UPD         0x6c
+
+/* BIT & MASK definition for SPRD_RTC_INT_* registers */
+#define SPRD_RTC_SEC_EN                 BIT(0)
+#define SPRD_RTC_MIN_EN                 BIT(1)
+#define SPRD_RTC_HOUR_EN                BIT(2)
+#define SPRD_RTC_DAY_EN                 BIT(3)
+#define SPRD_RTC_ALARM_EN               BIT(4)
+#define SPRD_RTC_HRS_FORMAT_EN          BIT(5)
+#define SPRD_RTC_AUXALM_EN              BIT(6)
+#define SPRD_RTC_SPG_UPD_EN             BIT(7)
+#define SPRD_RTC_SEC_UPD_EN             BIT(8)
+#define SPRD_RTC_MIN_UPD_EN             BIT(9)
+#define SPRD_RTC_HOUR_UPD_EN            BIT(10)
+#define SPRD_RTC_DAY_UPD_EN             BIT(11)
+#define SPRD_RTC_ALMSEC_UPD_EN          BIT(12)
+#define SPRD_RTC_ALMMIN_UPD_EN          BIT(13)
+#define SPRD_RTC_ALMHOUR_UPD_EN         BIT(14)
+#define SPRD_RTC_ALMDAY_UPD_EN          BIT(15)
+#define SPRD_RTC_INT_MASK               GENMASK(15, 0)
+
+#define SPRD_RTC_TIME_INT_MASK                          \
+        (SPRD_RTC_SEC_UPD_EN | SPRD_RTC_MIN_UPD_EN |    \
+         SPRD_RTC_HOUR_UPD_EN | SPRD_RTC_DAY_UPD_EN)
+
+#define SPRD_RTC_ALMTIME_INT_MASK                               \
+        (SPRD_RTC_ALMSEC_UPD_EN | SPRD_RTC_ALMMIN_UPD_EN |      \
+         SPRD_RTC_ALMHOUR_UPD_EN | SPRD_RTC_ALMDAY_UPD_EN)
+
+#define SPRD_RTC_ALM_INT_MASK                   \
+        (SPRD_RTC_SEC_EN | SPRD_RTC_MIN_EN |    \
+         SPRD_RTC_HOUR_EN | SPRD_RTC_DAY_EN |   \
+         SPRD_RTC_ALARM_EN | SPRD_RTC_AUXALM_EN)
+
+/* second/minute/hour/day values mask definition */
+#define SPRD_RTC_SEC_MASK               GENMASK(5, 0)
+#define SPRD_RTC_MIN_MASK               GENMASK(5, 0)
+#define SPRD_RTC_HOUR_MASK              GENMASK(4, 0)
+#define SPRD_RTC_DAY_MASK               GENMASK(15, 0)
+
+/* alarm lock definition for SPRD_RTC_SPG_UPD register */
+#define SPRD_RTC_ALMLOCK_MASK           GENMASK(7, 0)
+#define SPRD_RTC_ALM_UNLOCK             0xa5
+#define SPRD_RTC_ALM_LOCK               (~SPRD_RTC_ALM_UNLOCK & \
+                                         SPRD_RTC_ALMLOCK_MASK)
+
+/* SPG values definition for SPRD_RTC_SPG_UPD register */
+#define SPRD_RTC_POWEROFF_ALM_FLAG      BIT(8)
+#define SPRD_RTC_POWER_RESET_FLAG       BIT(9)
+
+/* timeout of synchronizing time and alarm registers (us) */
+#define SPRD_RTC_POLL_TIMEOUT           200000
+#define SPRD_RTC_POLL_DELAY_US          20000
+
+struct sprd_rtc {
+        struct rtc_device       *rtc;
+        struct regmap           *regmap;
+        struct device           *dev;
+        u32                     base;
+        int                     irq;
+        bool                    valid;
+};
+
+/*
+ * The Spreadtrum RTC controller has 3 groups registers, including time, normal
+ * alarm and auxiliary alarm. The time group registers are used to set RTC time,
+ * the normal alarm registers are used to set normal alarm, and the auxiliary
+ * alarm registers are used to set auxiliary alarm. Both alarm event and
+ * auxiliary alarm event can wake up system from deep sleep, but only alarm
+ * event can power up system from power down status.
+ */
+enum sprd_rtc_reg_types {
+        SPRD_RTC_TIME,
+        SPRD_RTC_ALARM,
+        SPRD_RTC_AUX_ALARM,
+};
+
+static int sprd_rtc_clear_alarm_ints(struct sprd_rtc *rtc)
+{
+        return regmap_write(rtc->regmap, rtc->base + SPRD_RTC_INT_CLR,
+                            SPRD_RTC_ALM_INT_MASK);
+}
+
+static int sprd_rtc_disable_ints(struct sprd_rtc *rtc)
+{
+        int ret;
+
+        ret = regmap_update_bits(rtc->regmap, rtc->base + SPRD_RTC_INT_EN,
+                                 SPRD_RTC_INT_MASK, 0);
+        if (ret)
+                return ret;
+
+        return regmap_write(rtc->regmap, rtc->base + SPRD_RTC_INT_CLR,
+                            SPRD_RTC_INT_MASK);
+}
+
+static int sprd_rtc_lock_alarm(struct sprd_rtc *rtc, bool lock)
+{
+        int ret;
+        u32 val;
+
+        ret = regmap_read(rtc->regmap, rtc->base + SPRD_RTC_SPG_VALUE, &val);
+        if (ret)
+                return ret;
+
+        val &= ~(SPRD_RTC_ALMLOCK_MASK | SPRD_RTC_POWEROFF_ALM_FLAG);
+        if (lock)
+                val |= SPRD_RTC_ALM_LOCK;
+        else
+                val |= SPRD_RTC_ALM_UNLOCK | SPRD_RTC_POWEROFF_ALM_FLAG;
+
+        ret = regmap_write(rtc->regmap, rtc->base + SPRD_RTC_SPG_UPD, val);
+        if (ret)
+                return ret;
+
+        /* wait until the SPG value is updated successfully */
+        ret = regmap_read_poll_timeout(rtc->regmap,
+                                       rtc->base + SPRD_RTC_INT_RAW_STS, val,
+                                       (val & SPRD_RTC_SPG_UPD_EN),
+                                       SPRD_RTC_POLL_DELAY_US,
+                                       SPRD_RTC_POLL_TIMEOUT);
+        if (ret) {
+                dev_err(rtc->dev, "failed to update SPG value:%d\n", ret);
+                return ret;
+        }
+
+        return 0;
+}
+
+static int sprd_rtc_get_secs(struct sprd_rtc *rtc, enum sprd_rtc_reg_types type,
+                             time64_t *secs)
+{
+        u32 sec_reg, min_reg, hour_reg, day_reg;
+        u32 val, sec, min, hour, day;
+        int ret;
+
+        switch (type) {
+        case SPRD_RTC_TIME:
+                sec_reg = SPRD_RTC_SEC_CNT_VALUE;
+                min_reg = SPRD_RTC_MIN_CNT_VALUE;
+                hour_reg = SPRD_RTC_HOUR_CNT_VALUE;
+                day_reg = SPRD_RTC_DAY_CNT_VALUE;
+                break;
+        case SPRD_RTC_ALARM:
+                sec_reg = SPRD_RTC_SEC_ALM_VALUE;
+                min_reg = SPRD_RTC_MIN_ALM_VALUE;
+                hour_reg = SPRD_RTC_HOUR_ALM_VALUE;
+                day_reg = SPRD_RTC_DAY_ALM_VALUE;
+                break;
+        case SPRD_RTC_AUX_ALARM:
+                sec_reg = SPRD_RTC_SEC_AUXALM_UPD;
+                min_reg = SPRD_RTC_MIN_AUXALM_UPD;
+                hour_reg = SPRD_RTC_HOUR_AUXALM_UPD;
+                day_reg = SPRD_RTC_DAY_AUXALM_UPD;
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        ret = regmap_read(rtc->regmap, rtc->base + sec_reg, &val);
+        if (ret)
+                return ret;
+
+        sec = val & SPRD_RTC_SEC_MASK;
+
+        ret = regmap_read(rtc->regmap, rtc->base + min_reg, &val);
+        if (ret)
+                return ret;
+
+        min = val & SPRD_RTC_MIN_MASK;
+
+        ret = regmap_read(rtc->regmap, rtc->base + hour_reg, &val);
+        if (ret)
+                return ret;
+
+        hour = val & SPRD_RTC_HOUR_MASK;
+
+        ret = regmap_read(rtc->regmap, rtc->base + day_reg, &val);
+        if (ret)
+                return ret;
+
+        day = val & SPRD_RTC_DAY_MASK;
+        *secs = (((time64_t)(day * 24) + hour) * 60 + min) * 60 + sec;
+        return 0;
+}
+
+static int sprd_rtc_set_secs(struct sprd_rtc *rtc, enum sprd_rtc_reg_types type,
+                             time64_t secs)
+{
+        u32 sec_reg, min_reg, hour_reg, day_reg, sts_mask;
+        u32 sec, min, hour, day, val;
+        int ret, rem;
+
+        /* convert seconds to RTC time format */
+        day = div_s64_rem(secs, 86400, &rem);
+        hour = rem / 3600;
+        rem -= hour * 3600;
+        min = rem / 60;
+        sec = rem - min * 60;
+
+        switch (type) {
+        case SPRD_RTC_TIME:
+                sec_reg = SPRD_RTC_SEC_CNT_UPD;
+                min_reg = SPRD_RTC_MIN_CNT_UPD;
+                hour_reg = SPRD_RTC_HOUR_CNT_UPD;
+                day_reg = SPRD_RTC_DAY_CNT_UPD;
+                sts_mask = SPRD_RTC_TIME_INT_MASK;
+                break;
+        case SPRD_RTC_ALARM:
+                sec_reg = SPRD_RTC_SEC_ALM_UPD;
+                min_reg = SPRD_RTC_MIN_ALM_UPD;
+                hour_reg = SPRD_RTC_HOUR_ALM_UPD;
+                day_reg = SPRD_RTC_DAY_ALM_UPD;
+                sts_mask = SPRD_RTC_ALMTIME_INT_MASK;
+                break;
+        case SPRD_RTC_AUX_ALARM:
+                sec_reg = SPRD_RTC_SEC_AUXALM_UPD;
+                min_reg = SPRD_RTC_MIN_AUXALM_UPD;
+                hour_reg = SPRD_RTC_HOUR_AUXALM_UPD;
+                day_reg = SPRD_RTC_DAY_AUXALM_UPD;
+                sts_mask = 0;
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        ret = regmap_write(rtc->regmap, rtc->base + sec_reg, sec);
+        if (ret)
+                return ret;
+
+        ret = regmap_write(rtc->regmap, rtc->base + min_reg, min);
+        if (ret)
+                return ret;
+
+        ret = regmap_write(rtc->regmap, rtc->base + hour_reg, hour);
+        if (ret)
+                return ret;
+
+        ret = regmap_write(rtc->regmap, rtc->base + day_reg, day);
+        if (ret)
+                return ret;
+
+        if (type == SPRD_RTC_AUX_ALARM)
+                return 0;
+
+        /*
+         * Since the time and normal alarm registers are put in always-power-on
+         * region supplied by VDDRTC, then these registers changing time will
+         * be very long, about 125ms. Thus here we should wait until all
+         * values are updated successfully.
+         */
+        ret = regmap_read_poll_timeout(rtc->regmap,
+                                       rtc->base + SPRD_RTC_INT_RAW_STS, val,
+                                       ((val & sts_mask) == sts_mask),
+                                       SPRD_RTC_POLL_DELAY_US,
+                                       SPRD_RTC_POLL_TIMEOUT);
+        if (ret < 0) {
+                dev_err(rtc->dev, "set time/alarm values timeout\n");
+                return ret;
+        }
+
+        return regmap_write(rtc->regmap, rtc->base + SPRD_RTC_INT_CLR,
+                            sts_mask);
+}
+
+static int sprd_rtc_read_aux_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+        struct sprd_rtc *rtc = dev_get_drvdata(dev);
+        time64_t secs;
+        u32 val;
+        int ret;
+
+        ret = sprd_rtc_get_secs(rtc, SPRD_RTC_AUX_ALARM, &secs);
+        if (ret)
+                return ret;
+
+        rtc_time64_to_tm(secs, &alrm->time);
+
+        ret = regmap_read(rtc->regmap, rtc->base + SPRD_RTC_INT_EN, &val);
+        if (ret)
+                return ret;
+
+        alrm->enabled = !!(val & SPRD_RTC_AUXALM_EN);
+
+        ret = regmap_read(rtc->regmap, rtc->base + SPRD_RTC_INT_RAW_STS, &val);
+        if (ret)
+                return ret;
+
+        alrm->pending = !!(val & SPRD_RTC_AUXALM_EN);
+        return 0;
+}
+
+static int sprd_rtc_set_aux_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+        struct sprd_rtc *rtc = dev_get_drvdata(dev);
+        time64_t secs = rtc_tm_to_time64(&alrm->time);
+        int ret;
+
+        /* clear the auxiliary alarm interrupt status */
+        ret = regmap_write(rtc->regmap, rtc->base + SPRD_RTC_INT_CLR,
+                           SPRD_RTC_AUXALM_EN);
+        if (ret)
+                return ret;
+
+        ret = sprd_rtc_set_secs(rtc, SPRD_RTC_AUX_ALARM, secs);
+        if (ret)
+                return ret;
+
+        if (alrm->enabled) {
+                ret = regmap_update_bits(rtc->regmap,
+                                         rtc->base + SPRD_RTC_INT_EN,
+                                         SPRD_RTC_AUXALM_EN,
+                                         SPRD_RTC_AUXALM_EN);
+        } else {
+                ret = regmap_update_bits(rtc->regmap,
+                                         rtc->base + SPRD_RTC_INT_EN,
+                                         SPRD_RTC_AUXALM_EN, 0);
+        }
+
+        return ret;
+}
+
+static int sprd_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+        struct sprd_rtc *rtc = dev_get_drvdata(dev);
+        time64_t secs;
+        int ret;
+
+        if (!rtc->valid) {
+                dev_warn(dev, "RTC values are invalid\n");
+                return -EINVAL;
+        }
+
+        ret = sprd_rtc_get_secs(rtc, SPRD_RTC_TIME, &secs);
+        if (ret)
+                return ret;
+
+        rtc_time64_to_tm(secs, tm);
+        return rtc_valid_tm(tm);
+}
+
+static int sprd_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+        struct sprd_rtc *rtc = dev_get_drvdata(dev);
+        time64_t secs = rtc_tm_to_time64(tm);
+        u32 val;
+        int ret;
+
+        ret = sprd_rtc_set_secs(rtc, SPRD_RTC_TIME, secs);
+        if (ret)
+                return ret;
+
+        if (!rtc->valid) {
+                /*
+                 * Set SPRD_RTC_POWER_RESET_FLAG to indicate now RTC has valid
+                 * time values.
+                 */
+                ret = regmap_update_bits(rtc->regmap,
+                                         rtc->base + SPRD_RTC_SPG_UPD,
+                                         SPRD_RTC_POWER_RESET_FLAG,
+                                         SPRD_RTC_POWER_RESET_FLAG);
+                if (ret)
+                        return ret;
+
+                ret = regmap_read_poll_timeout(rtc->regmap,
+                                               rtc->base + SPRD_RTC_INT_RAW_STS,
+                                               val, (val & SPRD_RTC_SPG_UPD_EN),
+                                               SPRD_RTC_POLL_DELAY_US,
+                                               SPRD_RTC_POLL_TIMEOUT);
+                if (ret) {
+                        dev_err(rtc->dev, "failed to update SPG value:%d\n",
+                                ret);
+                        return ret;
+                }
+
+                rtc->valid = true;
+        }
+
+        return 0;
+}
+
+static int sprd_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+        struct sprd_rtc *rtc = dev_get_drvdata(dev);
+        time64_t secs;
+        int ret;
+        u32 val;
+
+        /*
+         * If aie_timer is enabled, we should get the normal alarm time.
+         * Otherwise we should get auxiliary alarm time.
+         */
+        if (rtc->rtc && rtc->rtc->aie_timer.enabled == 0)
+                return sprd_rtc_read_aux_alarm(dev, alrm);
+
+        ret = sprd_rtc_get_secs(rtc, SPRD_RTC_ALARM, &secs);
+        if (ret)
+                return ret;
+
+        rtc_time64_to_tm(secs, &alrm->time);
+
+        ret = regmap_read(rtc->regmap, rtc->base + SPRD_RTC_INT_EN, &val);
+        if (ret)
+                return ret;
+
+        alrm->enabled = !!(val & SPRD_RTC_ALARM_EN);
+
+        ret = regmap_read(rtc->regmap, rtc->base + SPRD_RTC_INT_RAW_STS, &val);
+        if (ret)
+                return ret;
+
+        alrm->pending = !!(val & SPRD_RTC_ALARM_EN);
+        return 0;
+}
+
+static int sprd_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+        struct sprd_rtc *rtc = dev_get_drvdata(dev);
+        time64_t secs = rtc_tm_to_time64(&alrm->time);
+        struct rtc_time aie_time =
+                rtc_ktime_to_tm(rtc->rtc->aie_timer.node.expires);
+        int ret;
+
+        /*
+         * We have 2 groups alarms: normal alarm and auxiliary alarm. Since
+         * both normal alarm event and auxiliary alarm event can wake up system
+         * from deep sleep, but only alarm event can power up system from power
+         * down status. Moreover we do not need to poll about 125ms when
+         * updating auxiliary alarm registers. Thus we usually set auxiliary
+         * alarm when wake up system from deep sleep, and for other scenarios,
+         * we should set normal alarm with polling status.
+         *
+         * So here we check if the alarm time is set by aie_timer, if yes, we
+         * should set normal alarm, if not, we should set auxiliary alarm which
+         * means it is just a wake event.
+         */
+        if (!rtc->rtc->aie_timer.enabled || rtc_tm_sub(&aie_time, &alrm->time))
+                return sprd_rtc_set_aux_alarm(dev, alrm);
+
+        /* clear the alarm interrupt status firstly */
+        ret = regmap_write(rtc->regmap, rtc->base + SPRD_RTC_INT_CLR,
+                           SPRD_RTC_ALARM_EN);
+        if (ret)
+                return ret;
+
+        ret = sprd_rtc_set_secs(rtc, SPRD_RTC_ALARM, secs);
+        if (ret)
+                return ret;
+
+        if (alrm->enabled) {
+                ret = regmap_update_bits(rtc->regmap,
+                                         rtc->base + SPRD_RTC_INT_EN,
+                                         SPRD_RTC_ALARM_EN,
+                                         SPRD_RTC_ALARM_EN);
+                if (ret)
+                        return ret;
+
+                /* unlock the alarm to enable the alarm function. */
+                ret = sprd_rtc_lock_alarm(rtc, false);
+        } else {
+                regmap_update_bits(rtc->regmap,
+                                   rtc->base + SPRD_RTC_INT_EN,
+                                   SPRD_RTC_ALARM_EN, 0);
+
+                /*
+                 * Lock the alarm function in case fake alarm event will power
+                 * up systems.
+                 */
+                ret = sprd_rtc_lock_alarm(rtc, true);
+        }
+
+        return ret;
+}
+
+static int sprd_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+        struct sprd_rtc *rtc = dev_get_drvdata(dev);
+        int ret;
+
+        if (enabled) {
+                ret = regmap_update_bits(rtc->regmap,
+                                         rtc->base + SPRD_RTC_INT_EN,
+                                         SPRD_RTC_ALARM_EN | SPRD_RTC_AUXALM_EN,
+                                         SPRD_RTC_ALARM_EN | SPRD_RTC_AUXALM_EN);
+                if (ret)
+                        return ret;
+
+                ret = sprd_rtc_lock_alarm(rtc, false);
+        } else {
+                regmap_update_bits(rtc->regmap, rtc->base + SPRD_RTC_INT_EN,
+                                   SPRD_RTC_ALARM_EN | SPRD_RTC_AUXALM_EN, 0);
+
+                ret = sprd_rtc_lock_alarm(rtc, true);
+        }
+
+        return ret;
+}
+
+static const struct rtc_class_ops sprd_rtc_ops = {
+        .read_time = sprd_rtc_read_time,
+        .set_time = sprd_rtc_set_time,
+        .read_alarm = sprd_rtc_read_alarm,
+        .set_alarm = sprd_rtc_set_alarm,
+        .alarm_irq_enable = sprd_rtc_alarm_irq_enable,
+};
+
+static irqreturn_t sprd_rtc_handler(int irq, void *dev_id)
+{
+        struct sprd_rtc *rtc = dev_id;
+        int ret;
+
+        ret = sprd_rtc_clear_alarm_ints(rtc);
+        if (ret)
+                return IRQ_RETVAL(ret);
+
+        rtc_update_irq(rtc->rtc, 1, RTC_AF | RTC_IRQF);
+        return IRQ_HANDLED;
+}
+
+static int sprd_rtc_check_power_down(struct sprd_rtc *rtc)
+{
+        u32 val;
+        int ret;
+
+        ret = regmap_read(rtc->regmap, rtc->base + SPRD_RTC_SPG_VALUE, &val);
+        if (ret)
+                return ret;
+
+        /*
+         * If the SPRD_RTC_POWER_RESET_FLAG was not set, which means the RTC has
+         * been powered down, so the RTC time values are invalid.
+         */
+        rtc->valid = (val & SPRD_RTC_POWER_RESET_FLAG) ? true : false;
+        return 0;
+}
+
+static int sprd_rtc_probe(struct platform_device *pdev)
+{
+        struct device_node *node = pdev->dev.of_node;
+        struct sprd_rtc *rtc;
+        int ret;
+
+        rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
+        if (!rtc)
+                return -ENOMEM;
+
+        rtc->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+        if (!rtc->regmap)
+                return -ENODEV;
+
+        ret = of_property_read_u32(node, "reg", &rtc->base);
+        if (ret) {
+                dev_err(&pdev->dev, "failed to get RTC base address\n");
+                return ret;
+        }
+
+        rtc->irq = platform_get_irq(pdev, 0);
+        if (rtc->irq < 0) {
+                dev_err(&pdev->dev, "failed to get RTC irq number\n");
+                return rtc->irq;
+        }
+
+        rtc->dev = &pdev->dev;
+        platform_set_drvdata(pdev, rtc);
+
+        /* clear all RTC interrupts and disable all RTC interrupts */
+        ret = sprd_rtc_disable_ints(rtc);
+        if (ret) {
+                dev_err(&pdev->dev, "failed to disable RTC interrupts\n");
+                return ret;
+        }
+
+        /* check if RTC time values are valid */
+        ret = sprd_rtc_check_power_down(rtc);
+        if (ret) {
+                dev_err(&pdev->dev, "failed to check RTC time values\n");
+                return ret;
+        }
+
+        ret = devm_request_threaded_irq(&pdev->dev, rtc->irq, NULL,
+                                        sprd_rtc_handler,
+                                        IRQF_ONESHOT | IRQF_EARLY_RESUME,
+                                        pdev->name, rtc);
+        if (ret < 0) {
+                dev_err(&pdev->dev, "failed to request RTC irq\n");
+                return ret;
+        }
+
+        rtc->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
+                                            &sprd_rtc_ops, THIS_MODULE);
+        if (IS_ERR(rtc->rtc))
+                return PTR_ERR(rtc->rtc);
+
+        device_init_wakeup(&pdev->dev, 1);
+        return 0;
+}
+
+static int sprd_rtc_remove(struct platform_device *pdev)
+{
+        device_init_wakeup(&pdev->dev, 0);
+        return 0;
+}
+
+static const struct of_device_id sprd_rtc_of_match[] = {
+        { .compatible = "sprd,sc2731-rtc", },
+        { },
+};
+MODULE_DEVICE_TABLE(of, sprd_rtc_of_match);
+
+static struct platform_driver sprd_rtc_driver = {
+        .driver = {
+                .name = "sprd-rtc",
+                .of_match_table = sprd_rtc_of_match,
+        },
+        .probe  = sprd_rtc_probe,
+        .remove = sprd_rtc_remove,
+};
+module_platform_driver(sprd_rtc_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Spreadtrum RTC Device Driver");
+MODULE_AUTHOR("Baolin Wang <baolin.wang@spreadtrum.com>");