rtc: add driver for RX6110SA real time clock

The RX6110 comes in two different variants: SPI and I2C.
This driver only supports the SPI variant.

If the need ever arises to also support the I2C variant, this driver
could easily be refactored to support both cases.

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

3 files changed, 412 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index d47ad96132bf..ec6a25324525 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -743,6 +743,15 @@ config RTC_DRV_RX4581
           This driver can also be built as a module. If so the module
           will be called rtc-rx4581.
 
+config RTC_DRV_RX6110
+        tristate "Epson RX-6110"
+        select REGMAP_SPI
+        help
+          If you say yes here you will get support for the Epson RX-6610.
+
+          This driver can also be built as a module. If so the module
+          will be called rtc-rx6110.
+
 config RTC_DRV_MCP795
         tristate "Microchip MCP795"
         help
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index ed4519efa3ca..c8a21479deea 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -127,6 +127,7 @@ obj-$(CONFIG_RTC_DRV_RS5C372)	+= rtc-rs5c372.o
 obj-$(CONFIG_RTC_DRV_RV3029C2)  += rtc-rv3029c2.o
 obj-$(CONFIG_RTC_DRV_RV8803)    += rtc-rv8803.o
 obj-$(CONFIG_RTC_DRV_RX4581)    += rtc-rx4581.o
+obj-$(CONFIG_RTC_DRV_RX6110)    += rtc-rx6110.o
 obj-$(CONFIG_RTC_DRV_RX8010)    += rtc-rx8010.o
 obj-$(CONFIG_RTC_DRV_RX8025)    += rtc-rx8025.o
 obj-$(CONFIG_RTC_DRV_RX8581)    += rtc-rx8581.o
diff --git a/drivers/rtc/rtc-rx6110.c b/drivers/rtc/rtc-rx6110.c
new file mode 100644
index 000000000000..bbad00b233bc
--- /dev/null
+++ b/drivers/rtc/rtc-rx6110.c
@@ -0,0 +1,402 @@
+/*
+ * Driver for the Epson RTC module RX-6110 SA
+ *
+ * Copyright(C) 2015 Pengutronix, Steffen Trumtrar <kernel@pengutronix.de>
+ * Copyright(C) SEIKO EPSON CORPORATION 2013. All rights reserved.
+ *
+ * This driver software is distributed as is, without any warranty of any kind,
+ * either express or implied as further specified in the GNU Public License.
+ * This software may be used and distributed according to the terms of the GNU
+ * Public License, version 2 as published by the Free Software Foundation.
+ * See the file COPYING in the main directory of this archive for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/bcd.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_gpio.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/spi/spi.h>
+
+/* RX-6110 Register definitions */
+#define RX6110_REG_SEC          0x10
+#define RX6110_REG_MIN          0x11
+#define RX6110_REG_HOUR         0x12
+#define RX6110_REG_WDAY         0x13
+#define RX6110_REG_MDAY         0x14
+#define RX6110_REG_MONTH        0x15
+#define RX6110_REG_YEAR         0x16
+#define RX6110_REG_RES1         0x17
+#define RX6110_REG_ALMIN        0x18
+#define RX6110_REG_ALHOUR       0x19
+#define RX6110_REG_ALWDAY       0x1A
+#define RX6110_REG_TCOUNT0      0x1B
+#define RX6110_REG_TCOUNT1      0x1C
+#define RX6110_REG_EXT          0x1D
+#define RX6110_REG_FLAG         0x1E
+#define RX6110_REG_CTRL         0x1F
+#define RX6110_REG_USER0        0x20
+#define RX6110_REG_USER1        0x21
+#define RX6110_REG_USER2        0x22
+#define RX6110_REG_USER3        0x23
+#define RX6110_REG_USER4        0x24
+#define RX6110_REG_USER5        0x25
+#define RX6110_REG_USER6        0x26
+#define RX6110_REG_USER7        0x27
+#define RX6110_REG_USER8        0x28
+#define RX6110_REG_USER9        0x29
+#define RX6110_REG_USERA        0x2A
+#define RX6110_REG_USERB        0x2B
+#define RX6110_REG_USERC        0x2C
+#define RX6110_REG_USERD        0x2D
+#define RX6110_REG_USERE        0x2E
+#define RX6110_REG_USERF        0x2F
+#define RX6110_REG_RES2         0x30
+#define RX6110_REG_RES3         0x31
+#define RX6110_REG_IRQ          0x32
+
+#define RX6110_BIT_ALARM_EN             BIT(7)
+
+/* Extension Register (1Dh) bit positions */
+#define RX6110_BIT_EXT_TSEL0            BIT(0)
+#define RX6110_BIT_EXT_TSEL1            BIT(1)
+#define RX6110_BIT_EXT_TSEL2            BIT(2)
+#define RX6110_BIT_EXT_WADA             BIT(3)
+#define RX6110_BIT_EXT_TE               BIT(4)
+#define RX6110_BIT_EXT_USEL             BIT(5)
+#define RX6110_BIT_EXT_FSEL0            BIT(6)
+#define RX6110_BIT_EXT_FSEL1            BIT(7)
+
+/* Flag Register (1Eh) bit positions */
+#define RX6110_BIT_FLAG_VLF             BIT(1)
+#define RX6110_BIT_FLAG_AF              BIT(3)
+#define RX6110_BIT_FLAG_TF              BIT(4)
+#define RX6110_BIT_FLAG_UF              BIT(5)
+
+/* Control Register (1Fh) bit positions */
+#define RX6110_BIT_CTRL_TBKE            BIT(0)
+#define RX6110_BIT_CTRL_TBKON           BIT(1)
+#define RX6110_BIT_CTRL_TSTP            BIT(2)
+#define RX6110_BIT_CTRL_AIE             BIT(3)
+#define RX6110_BIT_CTRL_TIE             BIT(4)
+#define RX6110_BIT_CTRL_UIE             BIT(5)
+#define RX6110_BIT_CTRL_STOP            BIT(6)
+#define RX6110_BIT_CTRL_TEST            BIT(7)
+
+enum {
+        RTC_SEC = 0,
+        RTC_MIN,
+        RTC_HOUR,
+        RTC_WDAY,
+        RTC_MDAY,
+        RTC_MONTH,
+        RTC_YEAR,
+        RTC_NR_TIME
+};
+
+#define RX6110_DRIVER_NAME              "rx6110"
+
+struct rx6110_data {
+        struct rtc_device *rtc;
+        struct regmap *regmap;
+};
+
+/**
+ * rx6110_rtc_tm_to_data - convert rtc_time to native time encoding
+ *
+ * @tm: holds date and time
+ * @data: holds the encoding in rx6110 native form
+ */
+static int rx6110_rtc_tm_to_data(struct rtc_time *tm, u8 *data)
+{
+        pr_debug("%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
+                 tm->tm_sec, tm->tm_min, tm->tm_hour,
+                 tm->tm_mday, tm->tm_mon, tm->tm_year);
+
+        /*
+         * The year in the RTC is a value between 0 and 99.
+         * Assume that this represents the current century
+         * and disregard all other values.
+         */
+        if (tm->tm_year < 100 || tm->tm_year >= 200)
+                return -EINVAL;
+
+        data[RTC_SEC] = bin2bcd(tm->tm_sec);
+        data[RTC_MIN] = bin2bcd(tm->tm_min);
+        data[RTC_HOUR] = bin2bcd(tm->tm_hour);
+        data[RTC_WDAY] = BIT(bin2bcd(tm->tm_wday));
+        data[RTC_MDAY] = bin2bcd(tm->tm_mday);
+        data[RTC_MONTH] = bin2bcd(tm->tm_mon + 1);
+        data[RTC_YEAR] = bin2bcd(tm->tm_year % 100);
+
+        return 0;
+}
+
+/**
+ * rx6110_data_to_rtc_tm - convert native time encoding to rtc_time
+ *
+ * @data: holds the encoding in rx6110 native form
+ * @tm: holds date and time
+ */
+static int rx6110_data_to_rtc_tm(u8 *data, struct rtc_time *tm)
+{
+        tm->tm_sec = bcd2bin(data[RTC_SEC] & 0x7f);
+        tm->tm_min = bcd2bin(data[RTC_MIN] & 0x7f);
+        /* only 24-hour clock */
+        tm->tm_hour = bcd2bin(data[RTC_HOUR] & 0x3f);
+        tm->tm_wday = ffs(data[RTC_WDAY] & 0x7f);
+        tm->tm_mday = bcd2bin(data[RTC_MDAY] & 0x3f);
+        tm->tm_mon = bcd2bin(data[RTC_MONTH] & 0x1f) - 1;
+        tm->tm_year = bcd2bin(data[RTC_YEAR]) + 100;
+
+        pr_debug("%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
+                 tm->tm_sec, tm->tm_min, tm->tm_hour,
+                 tm->tm_mday, tm->tm_mon, tm->tm_year);
+
+        /*
+         * The year in the RTC is a value between 0 and 99.
+         * Assume that this represents the current century
+         * and disregard all other values.
+         */
+        if (tm->tm_year < 100 || tm->tm_year >= 200)
+                return -EINVAL;
+
+        return 0;
+}
+
+/**
+ * rx6110_set_time - set the current time in the rx6110 registers
+ *
+ * @dev: the rtc device in use
+ * @tm: holds date and time
+ *
+ * BUG: The HW assumes every year that is a multiple of 4 to be a leap
+ * year. Next time this is wrong is 2100, which will not be a leap year
+ *
+ * Note: If STOP is not set/cleared, the clock will start when the seconds
+ *       register is written
+ *
+ */
+static int rx6110_set_time(struct device *dev, struct rtc_time *tm)
+{
+        struct rx6110_data *rx6110 = dev_get_drvdata(dev);
+        u8 data[RTC_NR_TIME];
+        int ret;
+
+        ret = rx6110_rtc_tm_to_data(tm, data);
+        if (ret < 0)
+                return ret;
+
+        /* set STOP bit before changing clock/calendar */
+        ret = regmap_update_bits(rx6110->regmap, RX6110_REG_CTRL,
+                                 RX6110_BIT_CTRL_STOP, RX6110_BIT_CTRL_STOP);
+        if (ret)
+                return ret;
+
+        ret = regmap_bulk_write(rx6110->regmap, RX6110_REG_SEC, data,
+                                RTC_NR_TIME);
+        if (ret)
+                return ret;
+
+        /* The time in the RTC is valid. Be sure to have VLF cleared. */
+        ret = regmap_update_bits(rx6110->regmap, RX6110_REG_FLAG,
+                                 RX6110_BIT_FLAG_VLF, 0);
+        if (ret)
+                return ret;
+
+        /* clear STOP bit after changing clock/calendar */
+        ret = regmap_update_bits(rx6110->regmap, RX6110_REG_CTRL,
+                                 RX6110_BIT_CTRL_STOP, 0);
+
+        return ret;
+}
+
+/**
+ * rx6110_get_time - get the current time from the rx6110 registers
+ * @dev: the rtc device in use
+ * @tm: holds date and time
+ */
+static int rx6110_get_time(struct device *dev, struct rtc_time *tm)
+{
+        struct rx6110_data *rx6110 = dev_get_drvdata(dev);
+        u8 data[RTC_NR_TIME];
+        int flags;
+        int ret;
+
+        ret = regmap_read(rx6110->regmap, RX6110_REG_FLAG, &flags);
+        if (ret)
+                return -EINVAL;
+
+        /* check for VLF Flag (set at power-on) */
+        if ((flags & RX6110_BIT_FLAG_VLF)) {
+                dev_warn(dev, "Voltage low, data is invalid.\n");
+                return -EINVAL;
+        }
+
+        /* read registers to date */
+        ret = regmap_bulk_read(rx6110->regmap, RX6110_REG_SEC, data,
+                               RTC_NR_TIME);
+        if (ret)
+                return ret;
+
+        ret = rx6110_data_to_rtc_tm(data, tm);
+        if (ret)
+                return ret;
+
+        dev_dbg(dev, "%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
+                tm->tm_sec, tm->tm_min, tm->tm_hour,
+                tm->tm_mday, tm->tm_mon, tm->tm_year);
+
+        return rtc_valid_tm(tm);
+}
+
+static const struct reg_sequence rx6110_default_regs[] = {
+        { RX6110_REG_RES1,   0xB8 },
+        { RX6110_REG_RES2,   0x00 },
+        { RX6110_REG_RES3,   0x10 },
+        { RX6110_REG_IRQ,    0x00 },
+        { RX6110_REG_ALMIN,  0x00 },
+        { RX6110_REG_ALHOUR, 0x00 },
+        { RX6110_REG_ALWDAY, 0x00 },
+};
+
+/**
+ * rx6110_init - initialize the rx6110 registers
+ *
+ * @rx6110: pointer to the rx6110 struct in use
+ *
+ */
+static int rx6110_init(struct rx6110_data *rx6110)
+{
+        struct rtc_device *rtc = rx6110->rtc;
+        int flags;
+        int ret;
+
+        ret = regmap_update_bits(rx6110->regmap, RX6110_REG_EXT,
+                                 RX6110_BIT_EXT_TE, 0);
+        if (ret)
+                return ret;
+
+        ret = regmap_register_patch(rx6110->regmap, rx6110_default_regs,
+                                    ARRAY_SIZE(rx6110_default_regs));
+        if (ret)
+                return ret;
+
+        ret = regmap_read(rx6110->regmap, RX6110_REG_FLAG, &flags);
+        if (ret)
+                return ret;
+
+        /* check for VLF Flag (set at power-on) */
+        if ((flags & RX6110_BIT_FLAG_VLF))
+                dev_warn(&rtc->dev, "Voltage low, data loss detected.\n");
+
+        /* check for Alarm Flag */
+        if (flags & RX6110_BIT_FLAG_AF)
+                dev_warn(&rtc->dev, "An alarm may have been missed.\n");
+
+        /* check for Periodic Timer Flag */
+        if (flags & RX6110_BIT_FLAG_TF)
+                dev_warn(&rtc->dev, "Periodic timer was detected\n");
+
+        /* check for Update Timer Flag */
+        if (flags & RX6110_BIT_FLAG_UF)
+                dev_warn(&rtc->dev, "Update timer was detected\n");
+
+        /* clear all flags BUT VLF */
+        ret = regmap_update_bits(rx6110->regmap, RX6110_REG_FLAG,
+                                 RX6110_BIT_FLAG_AF |
+                                 RX6110_BIT_FLAG_UF |
+                                 RX6110_BIT_FLAG_TF,
+                                 0);
+
+        return ret;
+}
+
+static struct rtc_class_ops rx6110_rtc_ops = {
+        .read_time = rx6110_get_time,
+        .set_time = rx6110_set_time,
+};
+
+static struct regmap_config regmap_spi_config = {
+        .reg_bits = 8,
+        .val_bits = 8,
+        .max_register = RX6110_REG_IRQ,
+        .read_flag_mask = 0x80,
+};
+
+/**
+ * rx6110_probe - initialize rtc driver
+ * @spi: pointer to spi device
+ */
+static int rx6110_probe(struct spi_device *spi)
+{
+        struct rx6110_data *rx6110;
+        int err;
+
+        if ((spi->bits_per_word && spi->bits_per_word != 8) ||
+            (spi->max_speed_hz > 2000000) ||
+            (spi->mode != (SPI_CS_HIGH | SPI_CPOL | SPI_CPHA))) {
+                dev_warn(&spi->dev, "SPI settings: bits_per_word: %d, max_speed_hz: %d, mode: %xh\n",
+                         spi->bits_per_word, spi->max_speed_hz, spi->mode);
+                dev_warn(&spi->dev, "driving device in an unsupported mode");
+        }
+
+        rx6110 = devm_kzalloc(&spi->dev, sizeof(*rx6110), GFP_KERNEL);
+        if (!rx6110)
+                return -ENOMEM;
+
+        rx6110->regmap = devm_regmap_init_spi(spi, &regmap_spi_config);
+        if (IS_ERR(rx6110->regmap)) {
+                dev_err(&spi->dev, "regmap init failed for rtc rx6110\n");
+                return PTR_ERR(rx6110->regmap);
+        }
+
+        spi_set_drvdata(spi, rx6110);
+
+        rx6110->rtc = devm_rtc_device_register(&spi->dev,
+                                               RX6110_DRIVER_NAME,
+                                               &rx6110_rtc_ops, THIS_MODULE);
+
+        if (IS_ERR(rx6110->rtc))
+                return PTR_ERR(rx6110->rtc);
+
+        err = rx6110_init(rx6110);
+        if (err)
+                return err;
+
+        rx6110->rtc->max_user_freq = 1;
+
+        return 0;
+}
+
+static int rx6110_remove(struct spi_device *spi)
+{
+        return 0;
+}
+
+static const struct spi_device_id rx6110_id[] = {
+        { "rx6110", 0 },
+        { }
+};
+MODULE_DEVICE_TABLE(spi, rx6110_id);
+
+static struct spi_driver rx6110_driver = {
+        .driver = {
+                .name = RX6110_DRIVER_NAME,
+                .owner = THIS_MODULE,
+        },
+        .probe          = rx6110_probe,
+        .remove         = rx6110_remove,
+        .id_table       = rx6110_id,
+};
+
+module_spi_driver(rx6110_driver);
+
+MODULE_AUTHOR("Val Krutov <val.krutov@erd.epson.com>");
+MODULE_DESCRIPTION("RX-6110 SA RTC driver");
+MODULE_LICENSE("GPL");