rtc: ac100: Add RTC driver for X-Powers AC100

X-Powers AC100 is a codec / RTC combo chip. This driver supports
the RTC sub-device.

The RTC block also has clock outputs and non-volatile storage.
Non-volatile storage wthin the RTC hardware is not supported.
Clock output support is added in the next patch.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

3 files changed, 336 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index e215f50794b6..7fc11cdfd27e 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -187,6 +187,16 @@ config RTC_DRV_ABX80X
           This driver can also be built as a module. If so, the module
           will be called rtc-abx80x.
 
+config RTC_DRV_AC100
+        tristate "X-Powers AC100"
+        depends on MFD_AC100
+        help
+          If you say yes here you get support for the real-time clock found
+          in X-Powers AC100 family peripheral ICs.
+
+          This driver can also be built as a module. If so, the module
+          will be called rtc-ac100.
+
 config RTC_DRV_AS3722
         tristate "ams AS3722 RTC driver"
         depends on MFD_AS3722
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 7cf7ad559c79..8fb994bacdf7 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -27,6 +27,7 @@ obj-$(CONFIG_RTC_DRV_AB3100)	+= rtc-ab3100.o
 obj-$(CONFIG_RTC_DRV_AB8500)    += rtc-ab8500.o
 obj-$(CONFIG_RTC_DRV_ABB5ZES3)  += rtc-ab-b5ze-s3.o
 obj-$(CONFIG_RTC_DRV_ABX80X)    += rtc-abx80x.o
+obj-$(CONFIG_RTC_DRV_AC100)     += rtc-ac100.o
 obj-$(CONFIG_RTC_DRV_ARMADA38X) += rtc-armada38x.o
 obj-$(CONFIG_RTC_DRV_AS3722)    += rtc-as3722.o
 obj-$(CONFIG_RTC_DRV_ASM9260)   += rtc-asm9260.o
diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c
new file mode 100644
index 000000000000..5a9ca89d04c7
--- /dev/null
+++ b/drivers/rtc/rtc-ac100.c
@@ -0,0 +1,325 @@
+/*
+ * RTC Driver for X-Powers AC100
+ *
+ * Copyright (c) 2016 Chen-Yu Tsai
+ *
+ * Chen-Yu Tsai <wens@csie.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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.
+ */
+
+#include <linux/bcd.h>
+#include <linux/device.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/mfd/ac100.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/types.h>
+
+/* Control register */
+#define AC100_RTC_CTRL_24HOUR   BIT(0)
+
+/* RTC */
+#define AC100_RTC_SEC_MASK      GENMASK(6, 0)
+#define AC100_RTC_MIN_MASK      GENMASK(6, 0)
+#define AC100_RTC_HOU_MASK      GENMASK(5, 0)
+#define AC100_RTC_WEE_MASK      GENMASK(2, 0)
+#define AC100_RTC_DAY_MASK      GENMASK(5, 0)
+#define AC100_RTC_MON_MASK      GENMASK(4, 0)
+#define AC100_RTC_YEA_MASK      GENMASK(7, 0)
+#define AC100_RTC_YEA_LEAP      BIT(15)
+#define AC100_RTC_UPD_TRIGGER   BIT(15)
+
+/* Alarm (wall clock) */
+#define AC100_ALM_INT_ENABLE    BIT(0)
+
+#define AC100_ALM_SEC_MASK      GENMASK(6, 0)
+#define AC100_ALM_MIN_MASK      GENMASK(6, 0)
+#define AC100_ALM_HOU_MASK      GENMASK(5, 0)
+#define AC100_ALM_WEE_MASK      GENMASK(2, 0)
+#define AC100_ALM_DAY_MASK      GENMASK(5, 0)
+#define AC100_ALM_MON_MASK      GENMASK(4, 0)
+#define AC100_ALM_YEA_MASK      GENMASK(7, 0)
+#define AC100_ALM_ENABLE_FLAG   BIT(15)
+#define AC100_ALM_UPD_TRIGGER   BIT(15)
+
+/*
+ * The year parameter passed to the driver is usually an offset relative to
+ * the year 1900. This macro is used to convert this offset to another one
+ * relative to the minimum year allowed by the hardware.
+ *
+ * The year range is 1970 - 2069. This range is selected to match Allwinner's
+ * driver.
+ */
+#define AC100_YEAR_MIN                          1970
+#define AC100_YEAR_MAX                          2069
+#define AC100_YEAR_OFF                          (AC100_YEAR_MIN - 1900)
+
+struct ac100_rtc_dev {
+        struct rtc_device *rtc;
+        struct device *dev;
+        struct regmap *regmap;
+        int irq;
+        unsigned long alarm;
+};
+
+static int ac100_rtc_get_time(struct device *dev, struct rtc_time *rtc_tm)
+{
+        struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
+        struct regmap *regmap = chip->regmap;
+        u16 reg[7];
+        int ret;
+
+        ret = regmap_bulk_read(regmap, AC100_RTC_SEC, reg, 7);
+        if (ret)
+                return ret;
+
+        rtc_tm->tm_sec  = bcd2bin(reg[0] & AC100_RTC_SEC_MASK);
+        rtc_tm->tm_min  = bcd2bin(reg[1] & AC100_RTC_MIN_MASK);
+        rtc_tm->tm_hour = bcd2bin(reg[2] & AC100_RTC_HOU_MASK);
+        rtc_tm->tm_wday = bcd2bin(reg[3] & AC100_RTC_WEE_MASK);
+        rtc_tm->tm_mday = bcd2bin(reg[4] & AC100_RTC_DAY_MASK);
+        rtc_tm->tm_mon  = bcd2bin(reg[5] & AC100_RTC_MON_MASK) - 1;
+        rtc_tm->tm_year = bcd2bin(reg[6] & AC100_RTC_YEA_MASK) +
+                          AC100_YEAR_OFF;
+
+        return rtc_valid_tm(rtc_tm);
+}
+
+static int ac100_rtc_set_time(struct device *dev, struct rtc_time *rtc_tm)
+{
+        struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
+        struct regmap *regmap = chip->regmap;
+        int year;
+        u16 reg[8];
+
+        /* our RTC has a limited year range... */
+        year = rtc_tm->tm_year - AC100_YEAR_OFF;
+        if (year < 0 || year > (AC100_YEAR_MAX - 1900)) {
+                dev_err(dev, "rtc only supports year in range %d - %d\n",
+                        AC100_YEAR_MIN, AC100_YEAR_MAX);
+                return -EINVAL;
+        }
+
+        /* convert to BCD */
+        reg[0] = bin2bcd(rtc_tm->tm_sec)     & AC100_RTC_SEC_MASK;
+        reg[1] = bin2bcd(rtc_tm->tm_min)     & AC100_RTC_MIN_MASK;
+        reg[2] = bin2bcd(rtc_tm->tm_hour)    & AC100_RTC_HOU_MASK;
+        reg[3] = bin2bcd(rtc_tm->tm_wday)    & AC100_RTC_WEE_MASK;
+        reg[4] = bin2bcd(rtc_tm->tm_mday)    & AC100_RTC_DAY_MASK;
+        reg[5] = bin2bcd(rtc_tm->tm_mon + 1) & AC100_RTC_MON_MASK;
+        reg[6] = bin2bcd(year)               & AC100_RTC_YEA_MASK;
+        /* trigger write */
+        reg[7] = AC100_RTC_UPD_TRIGGER;
+
+        /* Is it a leap year? */
+        if (is_leap_year(year + AC100_YEAR_OFF + 1900))
+                reg[6] |= AC100_RTC_YEA_LEAP;
+
+        return regmap_bulk_write(regmap, AC100_RTC_SEC, reg, 8);
+}
+
+static int ac100_rtc_alarm_irq_enable(struct device *dev, unsigned int en)
+{
+        struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
+        struct regmap *regmap = chip->regmap;
+        unsigned int val;
+
+        val = en ? AC100_ALM_INT_ENABLE : 0;
+
+        return regmap_write(regmap, AC100_ALM_INT_ENA, val);
+}
+
+static int ac100_rtc_get_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+        struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
+        struct regmap *regmap = chip->regmap;
+        struct rtc_time *alrm_tm = &alrm->time;
+        u16 reg[7];
+        unsigned int val;
+        int ret;
+
+        ret = regmap_read(regmap, AC100_ALM_INT_ENA, &val);
+        if (ret)
+                return ret;
+
+        alrm->enabled = !!(val & AC100_ALM_INT_ENABLE);
+
+        ret = regmap_bulk_read(regmap, AC100_ALM_SEC, reg, 7);
+        if (ret)
+                return ret;
+
+        alrm_tm->tm_sec  = bcd2bin(reg[0] & AC100_ALM_SEC_MASK);
+        alrm_tm->tm_min  = bcd2bin(reg[1] & AC100_ALM_MIN_MASK);
+        alrm_tm->tm_hour = bcd2bin(reg[2] & AC100_ALM_HOU_MASK);
+        alrm_tm->tm_wday = bcd2bin(reg[3] & AC100_ALM_WEE_MASK);
+        alrm_tm->tm_mday = bcd2bin(reg[4] & AC100_ALM_DAY_MASK);
+        alrm_tm->tm_mon  = bcd2bin(reg[5] & AC100_ALM_MON_MASK) - 1;
+        alrm_tm->tm_year = bcd2bin(reg[6] & AC100_ALM_YEA_MASK) +
+                           AC100_YEAR_OFF;
+
+        return 0;
+}
+
+static int ac100_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+        struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
+        struct regmap *regmap = chip->regmap;
+        struct rtc_time *alrm_tm = &alrm->time;
+        u16 reg[8];
+        int year;
+        int ret;
+
+        /* our alarm has a limited year range... */
+        year = alrm_tm->tm_year - AC100_YEAR_OFF;
+        if (year < 0 || year > (AC100_YEAR_MAX - 1900)) {
+                dev_err(dev, "alarm only supports year in range %d - %d\n",
+                        AC100_YEAR_MIN, AC100_YEAR_MAX);
+                return -EINVAL;
+        }
+
+        /* convert to BCD */
+        reg[0] = (bin2bcd(alrm_tm->tm_sec)  & AC100_ALM_SEC_MASK) |
+                        AC100_ALM_ENABLE_FLAG;
+        reg[1] = (bin2bcd(alrm_tm->tm_min)  & AC100_ALM_MIN_MASK) |
+                        AC100_ALM_ENABLE_FLAG;
+        reg[2] = (bin2bcd(alrm_tm->tm_hour) & AC100_ALM_HOU_MASK) |
+                        AC100_ALM_ENABLE_FLAG;
+        /* Do not enable weekday alarm */
+        reg[3] = bin2bcd(alrm_tm->tm_wday) & AC100_ALM_WEE_MASK;
+        reg[4] = (bin2bcd(alrm_tm->tm_mday) & AC100_ALM_DAY_MASK) |
+                        AC100_ALM_ENABLE_FLAG;
+        reg[5] = (bin2bcd(alrm_tm->tm_mon + 1)  & AC100_ALM_MON_MASK) |
+                        AC100_ALM_ENABLE_FLAG;
+        reg[6] = (bin2bcd(year) & AC100_ALM_YEA_MASK) |
+                        AC100_ALM_ENABLE_FLAG;
+        /* trigger write */
+        reg[7] = AC100_ALM_UPD_TRIGGER;
+
+        ret = regmap_bulk_write(regmap, AC100_ALM_SEC, reg, 8);
+        if (ret)
+                return ret;
+
+        return ac100_rtc_alarm_irq_enable(dev, alrm->enabled);
+}
+
+static irqreturn_t ac100_rtc_irq(int irq, void *data)
+{
+        struct ac100_rtc_dev *chip = data;
+        struct regmap *regmap = chip->regmap;
+        unsigned int val = 0;
+        int ret;
+
+        mutex_lock(&chip->rtc->ops_lock);
+
+        /* read status */
+        ret = regmap_read(regmap, AC100_ALM_INT_STA, &val);
+        if (ret)
+                goto out;
+
+        if (val & AC100_ALM_INT_ENABLE) {
+                /* signal rtc framework */
+                rtc_update_irq(chip->rtc, 1, RTC_AF | RTC_IRQF);
+
+                /* clear status */
+                ret = regmap_write(regmap, AC100_ALM_INT_STA, val);
+                if (ret)
+                        goto out;
+
+                /* disable interrupt */
+                ret = ac100_rtc_alarm_irq_enable(chip->dev, 0);
+                if (ret)
+                        goto out;
+        }
+
+out:
+        mutex_unlock(&chip->rtc->ops_lock);
+        return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops ac100_rtc_ops = {
+        .read_time        = ac100_rtc_get_time,
+        .set_time         = ac100_rtc_set_time,
+        .read_alarm       = ac100_rtc_get_alarm,
+        .set_alarm        = ac100_rtc_set_alarm,
+        .alarm_irq_enable = ac100_rtc_alarm_irq_enable,
+};
+
+static int ac100_rtc_probe(struct platform_device *pdev)
+{
+        struct ac100_dev *ac100 = dev_get_drvdata(pdev->dev.parent);
+        struct ac100_rtc_dev *chip;
+        int ret;
+
+        chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
+        platform_set_drvdata(pdev, chip);
+        chip->dev = &pdev->dev;
+        chip->regmap = ac100->regmap;
+
+        chip->irq = platform_get_irq(pdev, 0);
+        if (chip->irq < 0) {
+                dev_err(&pdev->dev, "No IRQ resource\n");
+                return chip->irq;
+        }
+
+        ret = devm_request_threaded_irq(&pdev->dev, chip->irq, NULL,
+                                        ac100_rtc_irq,
+                                        IRQF_SHARED | IRQF_ONESHOT,
+                                        dev_name(&pdev->dev), chip);
+        if (ret) {
+                dev_err(&pdev->dev, "Could not request IRQ\n");
+                return ret;
+        }
+
+        /* always use 24 hour mode */
+        regmap_write_bits(chip->regmap, AC100_RTC_CTRL, AC100_RTC_CTRL_24HOUR,
+                          AC100_RTC_CTRL_24HOUR);
+
+        /* disable counter alarm interrupt */
+        regmap_write(chip->regmap, AC100_ALM_INT_ENA, 0);
+
+        /* clear counter alarm pending interrupts */
+        regmap_write(chip->regmap, AC100_ALM_INT_STA, AC100_ALM_INT_ENABLE);
+
+        chip->rtc = devm_rtc_device_register(&pdev->dev, "rtc-ac100",
+                                             &ac100_rtc_ops, THIS_MODULE);
+        if (IS_ERR(chip->rtc)) {
+                dev_err(&pdev->dev, "unable to register device\n");
+                return PTR_ERR(chip->rtc);
+        }
+
+        dev_info(&pdev->dev, "RTC enabled\n");
+
+        return 0;
+}
+
+static const struct of_device_id ac100_rtc_match[] = {
+        { .compatible = "x-powers,ac100-rtc" },
+        { },
+};
+MODULE_DEVICE_TABLE(of, ac100_rtc_match);
+
+static struct platform_driver ac100_rtc_driver = {
+        .probe          = ac100_rtc_probe,
+        .driver         = {
+                .name           = "ac100-rtc",
+                .of_match_table = of_match_ptr(ac100_rtc_match),
+        },
+};
+module_platform_driver(ac100_rtc_driver);
+
+MODULE_DESCRIPTION("X-Powers AC100 RTC driver");
+MODULE_AUTHOR("Chen-Yu Tsai <wens@csie.org>");
+MODULE_LICENSE("GPL v2");