rtc: Add support for Intersil ISL12057 I2C RTC chip

Intersil ISL12057 is an I2C RTC chip also supporting two alarms. This
patch only adds support for basic RTC functionalities (i.e. getting
and setting time). Tests have been performed on NETGEAR ReadyNAS 102
w/ startup/shutdown scripts, hwclock, ntpdate and openntpd.

Reviewed-by: Mark Brown <broonie@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

5 files changed, 324 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/i2c/trivial-devices.txt b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
index b1cb3415e6f1..cdf14308ed92 100644
--- a/Documentation/devicetree/bindings/i2c/trivial-devices.txt
+++ b/Documentation/devicetree/bindings/i2c/trivial-devices.txt
@@ -39,6 +39,7 @@ fsl,sgtl5000		SGTL5000: Ultra Low-Power Audio Codec
 gmt,g751                G751: Digital Temperature Sensor and Thermal Watchdog with Two-Wire Interface
 infineon,slb9635tt      Infineon SLB9635 (Soft-) I2C TPM (old protocol, max 100khz)
 infineon,slb9645tt      Infineon SLB9645 I2C TPM (new protocol, max 400khz)
+isl,isl12057            Intersil ISL12057 I2C RTC Chip
 maxim,ds1050            5 Bit Programmable, Pulse-Width Modulator
 maxim,max1237           Low-Power, 4-/12-Channel, 2-Wire Serial, 12-Bit ADCs
 maxim,max6625           9-Bit/12-Bit Temperature Sensors with I²C-Compatible Serial Interface
diff --git a/Documentation/devicetree/bindings/vendor-prefixes.txt b/Documentation/devicetree/bindings/vendor-prefixes.txt
index ce95ed1c6d3e..507761a22867 100644
--- a/Documentation/devicetree/bindings/vendor-prefixes.txt
+++ b/Documentation/devicetree/bindings/vendor-prefixes.txt
@@ -38,6 +38,7 @@ ibm	International Business Machines (IBM)
 idt     Integrated Device Technologies, Inc.
 img     Imagination Technologies Ltd.
 intercontrol    Inter Control Group
+isl     Intersil
 linux   Linux-specific binding
 lsi     LSI Corp. (LSI Logic)
 marvell Marvell Technology Group Ltd.
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 007730222116..9608210109f9 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -304,6 +304,17 @@ config RTC_DRV_ISL12022
           This driver can also be built as a module. If so, the module
           will be called rtc-isl12022.
 
+config RTC_DRV_ISL12057
+       depends on I2C
+       select REGMAP_I2C
+       tristate "Intersil ISL12057"
+       help
+          If you say yes here you get support for the Intersil ISL12057
+          I2C RTC chip.
+
+          This driver can also be built as a module. If so, the module
+          will be called rtc-isl12057.
+
 config RTC_DRV_X1205
         tristate "Xicor/Intersil X1205"
         help
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 27b4bd884066..d4089c0dbe91 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -58,6 +58,7 @@ obj-$(CONFIG_RTC_DRV_HID_SENSOR_TIME) += rtc-hid-sensor-time.o
 obj-$(CONFIG_RTC_DRV_IMXDI)     += rtc-imxdi.o
 obj-$(CONFIG_RTC_DRV_ISL1208)   += rtc-isl1208.o
 obj-$(CONFIG_RTC_DRV_ISL12022)  += rtc-isl12022.o
+obj-$(CONFIG_RTC_DRV_ISL12057)  += rtc-isl12057.o
 obj-$(CONFIG_RTC_DRV_JZ4740)    += rtc-jz4740.o
 obj-$(CONFIG_RTC_DRV_LP8788)    += rtc-lp8788.o
 obj-$(CONFIG_RTC_DRV_LPC32XX)   += rtc-lpc32xx.o
diff --git a/drivers/rtc/rtc-isl12057.c b/drivers/rtc/rtc-isl12057.c
new file mode 100644
index 000000000000..7854a656628f
--- /dev/null
+++ b/drivers/rtc/rtc-isl12057.c
@@ -0,0 +1,310 @@
+/*
+ * rtc-isl12057 - Driver for Intersil ISL12057 I2C Real Time Clock
+ *
+ * Copyright (C) 2013, Arnaud EBALARD <arno@natisbad.org>
+ *
+ * This work is largely based on Intersil ISL1208 driver developed by
+ * Hebert Valerio Riedel <hvr@gnu.org>.
+ *
+ * Detailed datasheet on which this development is based is available here:
+ *
+ *  http://natisbad.org/NAS2/refs/ISL12057.pdf
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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/module.h>
+#include <linux/mutex.h>
+#include <linux/rtc.h>
+#include <linux/i2c.h>
+#include <linux/bcd.h>
+#include <linux/rtc.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+
+#define DRV_NAME "rtc-isl12057"
+
+/* RTC section */
+#define ISL12057_REG_RTC_SC     0x00    /* Seconds */
+#define ISL12057_REG_RTC_MN     0x01    /* Minutes */
+#define ISL12057_REG_RTC_HR     0x02    /* Hours */
+#define ISL12057_REG_RTC_HR_PM  BIT(5)  /* AM/PM bit in 12h format */
+#define ISL12057_REG_RTC_HR_MIL BIT(6)  /* 24h/12h format */
+#define ISL12057_REG_RTC_DW     0x03    /* Day of the Week */
+#define ISL12057_REG_RTC_DT     0x04    /* Date */
+#define ISL12057_REG_RTC_MO     0x05    /* Month */
+#define ISL12057_REG_RTC_YR     0x06    /* Year */
+#define ISL12057_RTC_SEC_LEN    7
+
+/* Alarm 1 section */
+#define ISL12057_REG_A1_SC      0x07    /* Alarm 1 Seconds */
+#define ISL12057_REG_A1_MN      0x08    /* Alarm 1 Minutes */
+#define ISL12057_REG_A1_HR      0x09    /* Alarm 1 Hours */
+#define ISL12057_REG_A1_HR_PM   BIT(5)  /* AM/PM bit in 12h format */
+#define ISL12057_REG_A1_HR_MIL  BIT(6)  /* 24h/12h format */
+#define ISL12057_REG_A1_DWDT    0x0A    /* Alarm 1 Date / Day of the week */
+#define ISL12057_REG_A1_DWDT_B  BIT(6)  /* DW / DT selection bit */
+#define ISL12057_A1_SEC_LEN     4
+
+/* Alarm 2 section */
+#define ISL12057_REG_A2_MN      0x0B    /* Alarm 2 Minutes */
+#define ISL12057_REG_A2_HR      0x0C    /* Alarm 2 Hours */
+#define ISL12057_REG_A2_DWDT    0x0D    /* Alarm 2 Date / Day of the week */
+#define ISL12057_A2_SEC_LEN     3
+
+/* Control/Status registers */
+#define ISL12057_REG_INT        0x0E
+#define ISL12057_REG_INT_A1IE   BIT(0)  /* Alarm 1 interrupt enable bit */
+#define ISL12057_REG_INT_A2IE   BIT(1)  /* Alarm 2 interrupt enable bit */
+#define ISL12057_REG_INT_INTCN  BIT(2)  /* Interrupt control enable bit */
+#define ISL12057_REG_INT_RS1    BIT(3)  /* Freq out control bit 1 */
+#define ISL12057_REG_INT_RS2    BIT(4)  /* Freq out control bit 2 */
+#define ISL12057_REG_INT_EOSC   BIT(7)  /* Oscillator enable bit */
+
+#define ISL12057_REG_SR         0x0F
+#define ISL12057_REG_SR_A1F     BIT(0)  /* Alarm 1 interrupt bit */
+#define ISL12057_REG_SR_A2F     BIT(1)  /* Alarm 2 interrupt bit */
+#define ISL12057_REG_SR_OSF     BIT(7)  /* Oscillator failure bit */
+
+/* Register memory map length */
+#define ISL12057_MEM_MAP_LEN    0x10
+
+struct isl12057_rtc_data {
+        struct regmap *regmap;
+        struct mutex lock;
+};
+
+static void isl12057_rtc_regs_to_tm(struct rtc_time *tm, u8 *regs)
+{
+        tm->tm_sec = bcd2bin(regs[ISL12057_REG_RTC_SC]);
+        tm->tm_min = bcd2bin(regs[ISL12057_REG_RTC_MN]);
+
+        if (regs[ISL12057_REG_RTC_HR] & ISL12057_REG_RTC_HR_MIL) { /* AM/PM */
+                tm->tm_hour = bcd2bin(regs[ISL12057_REG_RTC_HR] & 0x0f);
+                if (regs[ISL12057_REG_RTC_HR] & ISL12057_REG_RTC_HR_PM)
+                        tm->tm_hour += 12;
+        } else {                                            /* 24 hour mode */
+                tm->tm_hour = bcd2bin(regs[ISL12057_REG_RTC_HR] & 0x3f);
+        }
+
+        tm->tm_mday = bcd2bin(regs[ISL12057_REG_RTC_DT]);
+        tm->tm_wday = bcd2bin(regs[ISL12057_REG_RTC_DW]) - 1; /* starts at 1 */
+        tm->tm_mon  = bcd2bin(regs[ISL12057_REG_RTC_MO]) - 1; /* starts at 1 */
+        tm->tm_year = bcd2bin(regs[ISL12057_REG_RTC_YR]) + 100;
+}
+
+static int isl12057_rtc_tm_to_regs(u8 *regs, struct rtc_time *tm)
+{
+        /*
+         * The clock has an 8 bit wide bcd-coded register for the year.
+         * tm_year is an offset from 1900 and we are interested in the
+         * 2000-2099 range, so any value less than 100 is invalid.
+         */
+        if (tm->tm_year < 100)
+                return -EINVAL;
+
+        regs[ISL12057_REG_RTC_SC] = bin2bcd(tm->tm_sec);
+        regs[ISL12057_REG_RTC_MN] = bin2bcd(tm->tm_min);
+        regs[ISL12057_REG_RTC_HR] = bin2bcd(tm->tm_hour); /* 24-hour format */
+        regs[ISL12057_REG_RTC_DT] = bin2bcd(tm->tm_mday);
+        regs[ISL12057_REG_RTC_MO] = bin2bcd(tm->tm_mon + 1);
+        regs[ISL12057_REG_RTC_YR] = bin2bcd(tm->tm_year - 100);
+        regs[ISL12057_REG_RTC_DW] = bin2bcd(tm->tm_wday + 1);
+
+        return 0;
+}
+
+/*
+ * Try and match register bits w/ fixed null values to see whether we
+ * are dealing with an ISL12057. Note: this function is called early
+ * during init and hence does need mutex protection.
+ */
+static int isl12057_i2c_validate_chip(struct regmap *regmap)
+{
+        u8 regs[ISL12057_MEM_MAP_LEN];
+        static const u8 mask[ISL12057_MEM_MAP_LEN] = { 0x80, 0x80, 0x80, 0xf8,
+                                                       0xc0, 0x60, 0x00, 0x00,
+                                                       0x00, 0x00, 0x00, 0x00,
+                                                       0x00, 0x00, 0x60, 0x7c };
+        int ret, i;
+
+        ret = regmap_bulk_read(regmap, 0, regs, ISL12057_MEM_MAP_LEN);
+        if (ret)
+                return ret;
+
+        for (i = 0; i < ISL12057_MEM_MAP_LEN; ++i) {
+                if (regs[i] & mask[i])  /* check if bits are cleared */
+                        return -ENODEV;
+        }
+
+        return 0;
+}
+
+static int isl12057_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+        struct isl12057_rtc_data *data = dev_get_drvdata(dev);
+        u8 regs[ISL12057_RTC_SEC_LEN];
+        int ret;
+
+        mutex_lock(&data->lock);
+        ret = regmap_bulk_read(data->regmap, ISL12057_REG_RTC_SC, regs,
+                               ISL12057_RTC_SEC_LEN);
+        mutex_unlock(&data->lock);
+
+        if (ret) {
+                dev_err(dev, "%s: RTC read failed\n", __func__);
+                return ret;
+        }
+
+        isl12057_rtc_regs_to_tm(tm, regs);
+
+        return rtc_valid_tm(tm);
+}
+
+static int isl12057_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+        struct isl12057_rtc_data *data = dev_get_drvdata(dev);
+        u8 regs[ISL12057_RTC_SEC_LEN];
+        int ret;
+
+        ret = isl12057_rtc_tm_to_regs(regs, tm);
+        if (ret)
+                return ret;
+
+        mutex_lock(&data->lock);
+        ret = regmap_bulk_write(data->regmap, ISL12057_REG_RTC_SC, regs,
+                                ISL12057_RTC_SEC_LEN);
+        mutex_unlock(&data->lock);
+
+        if (ret)
+                dev_err(dev, "%s: RTC write failed\n", __func__);
+
+        return ret;
+}
+
+/*
+ * Check current RTC status and enable/disable what needs to be. Return 0 if
+ * everything went ok and a negative value upon error. Note: this function
+ * is called early during init and hence does need mutex protection.
+ */
+static int isl12057_check_rtc_status(struct device *dev, struct regmap *regmap)
+{
+        int ret;
+
+        /* Enable oscillator if not already running */
+        ret = regmap_update_bits(regmap, ISL12057_REG_INT,
+                                 ISL12057_REG_INT_EOSC, 0);
+        if (ret < 0) {
+                dev_err(dev, "Unable to enable oscillator\n");
+                return ret;
+        }
+
+        /* Clear oscillator failure bit if needed */
+        ret = regmap_update_bits(regmap, ISL12057_REG_SR,
+                                 ISL12057_REG_SR_OSF, 0);
+        if (ret < 0) {
+                dev_err(dev, "Unable to clear oscillator failure bit\n");
+                return ret;
+        }
+
+        /* Clear alarm bit if needed */
+        ret = regmap_update_bits(regmap, ISL12057_REG_SR,
+                                 ISL12057_REG_SR_A1F, 0);
+        if (ret < 0) {
+                dev_err(dev, "Unable to clear alarm bit\n");
+                return ret;
+        }
+
+        return 0;
+}
+
+static const struct rtc_class_ops rtc_ops = {
+        .read_time = isl12057_rtc_read_time,
+        .set_time = isl12057_rtc_set_time,
+};
+
+static struct regmap_config isl12057_rtc_regmap_config = {
+        .reg_bits = 8,
+        .val_bits = 8,
+};
+
+static int isl12057_probe(struct i2c_client *client,
+                          const struct i2c_device_id *id)
+{
+        struct device *dev = &client->dev;
+        struct isl12057_rtc_data *data;
+        struct rtc_device *rtc;
+        struct regmap *regmap;
+        int ret;
+
+        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
+                                     I2C_FUNC_SMBUS_BYTE_DATA |
+                                     I2C_FUNC_SMBUS_I2C_BLOCK))
+                return -ENODEV;
+
+        regmap = devm_regmap_init_i2c(client, &isl12057_rtc_regmap_config);
+        if (IS_ERR(regmap)) {
+                ret = PTR_ERR(regmap);
+                dev_err(dev, "regmap allocation failed: %d\n", ret);
+                return ret;
+        }
+
+        ret = isl12057_i2c_validate_chip(regmap);
+        if (ret)
+                return ret;
+
+        ret = isl12057_check_rtc_status(dev, regmap);
+        if (ret)
+                return ret;
+
+        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+
+        mutex_init(&data->lock);
+        data->regmap = regmap;
+        dev_set_drvdata(dev, data);
+
+        rtc = devm_rtc_device_register(dev, DRV_NAME, &rtc_ops, THIS_MODULE);
+        if (IS_ERR(rtc))
+                return PTR_ERR(rtc);
+
+        return 0;
+}
+
+#ifdef CONFIG_OF
+static struct of_device_id isl12057_dt_match[] = {
+        { .compatible = "isl,isl12057" },
+        { },
+};
+#endif
+
+static const struct i2c_device_id isl12057_id[] = {
+        { "isl12057", 0 },
+        { }
+};
+MODULE_DEVICE_TABLE(i2c, isl12057_id);
+
+static struct i2c_driver isl12057_driver = {
+        .driver = {
+                .name = DRV_NAME,
+                .owner = THIS_MODULE,
+                .of_match_table = of_match_ptr(isl12057_dt_match),
+        },
+        .probe    = isl12057_probe,
+        .id_table = isl12057_id,
+};
+module_i2c_driver(isl12057_driver);
+
+MODULE_AUTHOR("Arnaud EBALARD <arno@natisbad.org>");
+MODULE_DESCRIPTION("Intersil ISL12057 RTC driver");
+MODULE_LICENSE("GPL");