rtc: add rtc-abx80x, a driver for the Abracon AB x80x i2c rtc

This is a basic driver for the ultra-low-power Abracon AB x80x series of RTC
chips. It supports in particular, the supersets AB0805 and AB1805.
It allows reading and writing the time, and enables the supercapacitor/
battery charger.

[arnd@arndb.de: abx805 depends on i2c]
[alexandre.belloni@free-electrons.com: renam buffer from date to buf in abx80x_rtc_read_time()]
Signed-off-by: Philippe De Muyter <phdm@macqel.be>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Paul Bolle <pebolle@tiscali.nl>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 318 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 6149ae01e11f..0fe4ad8826b2 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -164,6 +164,16 @@ config RTC_DRV_ABB5ZES3
           This driver can also be built as a module. If so, the module
           will be called rtc-ab-b5ze-s3.
 
+config RTC_DRV_ABX80X
+        tristate "Abracon ABx80x"
+        help
+          If you say yes here you get support for Abracon AB080X and AB180X
+          families of ultra-low-power  battery- and capacitor-backed real-time
+          clock chips.
+
+          This driver can also be built as a module. If so, the module
+          will be called rtc-abx80x.
+
 config RTC_DRV_AS3722
         tristate "ams AS3722 RTC driver"
         depends on MFD_AS3722
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index c31731c29762..2b82e2b0311b 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -25,6 +25,7 @@ obj-$(CONFIG_RTC_DRV_88PM80X)	+= rtc-88pm80x.o
 obj-$(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_ARMADA38X) += rtc-armada38x.o
 obj-$(CONFIG_RTC_DRV_AS3722)    += rtc-as3722.o
 obj-$(CONFIG_RTC_DRV_AT32AP700X)+= rtc-at32ap700x.o
diff --git a/drivers/rtc/rtc-abx80x.c b/drivers/rtc/rtc-abx80x.c
new file mode 100644
index 000000000000..4337c3bc6ace
--- /dev/null
+++ b/drivers/rtc/rtc-abx80x.c
@@ -0,0 +1,307 @@
+/*
+ * A driver for the I2C members of the Abracon AB x8xx RTC family,
+ * and compatible: AB 1805 and AB 0805
+ *
+ * Copyright 2014-2015 Macq S.A.
+ *
+ * Author: Philippe De Muyter <phdm@macqel.be>
+ * Author: Alexandre Belloni <alexandre.belloni@free-electrons.com>
+ *
+ * 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.
+ *
+ */
+
+#include <linux/bcd.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/rtc.h>
+
+#define ABX8XX_REG_HTH          0x00
+#define ABX8XX_REG_SC           0x01
+#define ABX8XX_REG_MN           0x02
+#define ABX8XX_REG_HR           0x03
+#define ABX8XX_REG_DA           0x04
+#define ABX8XX_REG_MO           0x05
+#define ABX8XX_REG_YR           0x06
+#define ABX8XX_REG_WD           0x07
+
+#define ABX8XX_REG_CTRL1        0x10
+#define ABX8XX_CTRL_WRITE       BIT(1)
+#define ABX8XX_CTRL_12_24       BIT(6)
+
+#define ABX8XX_REG_CFG_KEY      0x1f
+#define ABX8XX_CFG_KEY_MISC     0x9d
+
+#define ABX8XX_REG_ID0          0x28
+
+#define ABX8XX_REG_TRICKLE      0x20
+#define ABX8XX_TRICKLE_CHARGE_ENABLE    0xa0
+#define ABX8XX_TRICKLE_STANDARD_DIODE   0x8
+#define ABX8XX_TRICKLE_SCHOTTKY_DIODE   0x4
+
+static u8 trickle_resistors[] = {0, 3, 6, 11};
+
+enum abx80x_chip {AB0801, AB0803, AB0804, AB0805,
+        AB1801, AB1803, AB1804, AB1805, ABX80X};
+
+struct abx80x_cap {
+        u16 pn;
+        bool has_tc;
+};
+
+static struct abx80x_cap abx80x_caps[] = {
+        [AB0801] = {.pn = 0x0801},
+        [AB0803] = {.pn = 0x0803},
+        [AB0804] = {.pn = 0x0804, .has_tc = true},
+        [AB0805] = {.pn = 0x0805, .has_tc = true},
+        [AB1801] = {.pn = 0x1801},
+        [AB1803] = {.pn = 0x1803},
+        [AB1804] = {.pn = 0x1804, .has_tc = true},
+        [AB1805] = {.pn = 0x1805, .has_tc = true},
+        [ABX80X] = {.pn = 0}
+};
+
+static struct i2c_driver abx80x_driver;
+
+static int abx80x_enable_trickle_charger(struct i2c_client *client,
+                                         u8 trickle_cfg)
+{
+        int err;
+
+        /*
+         * Write the configuration key register to enable access to the Trickle
+         * register
+         */
+        err = i2c_smbus_write_byte_data(client, ABX8XX_REG_CFG_KEY,
+                                        ABX8XX_CFG_KEY_MISC);
+        if (err < 0) {
+                dev_err(&client->dev, "Unable to write configuration key\n");
+                return -EIO;
+        }
+
+        err = i2c_smbus_write_byte_data(client, ABX8XX_REG_TRICKLE,
+                                        ABX8XX_TRICKLE_CHARGE_ENABLE |
+                                        trickle_cfg);
+        if (err < 0) {
+                dev_err(&client->dev, "Unable to write trickle register\n");
+                return -EIO;
+        }
+
+        return 0;
+}
+
+static int abx80x_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+        struct i2c_client *client = to_i2c_client(dev);
+        unsigned char buf[8];
+        int err;
+
+        err = i2c_smbus_read_i2c_block_data(client, ABX8XX_REG_HTH,
+                                            sizeof(buf), buf);
+        if (err < 0) {
+                dev_err(&client->dev, "Unable to read date\n");
+                return -EIO;
+        }
+
+        tm->tm_sec = bcd2bin(buf[ABX8XX_REG_SC] & 0x7F);
+        tm->tm_min = bcd2bin(buf[ABX8XX_REG_MN] & 0x7F);
+        tm->tm_hour = bcd2bin(buf[ABX8XX_REG_HR] & 0x3F);
+        tm->tm_wday = buf[ABX8XX_REG_WD] & 0x7;
+        tm->tm_mday = bcd2bin(buf[ABX8XX_REG_DA] & 0x3F);
+        tm->tm_mon = bcd2bin(buf[ABX8XX_REG_MO] & 0x1F) - 1;
+        tm->tm_year = bcd2bin(buf[ABX8XX_REG_YR]) + 100;
+
+        err = rtc_valid_tm(tm);
+        if (err < 0)
+                dev_err(&client->dev, "retrieved date/time is not valid.\n");
+
+        return err;
+}
+
+static int abx80x_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+        struct i2c_client *client = to_i2c_client(dev);
+        unsigned char buf[8];
+        int err;
+
+        if (tm->tm_year < 100)
+                return -EINVAL;
+
+        buf[ABX8XX_REG_HTH] = 0;
+        buf[ABX8XX_REG_SC] = bin2bcd(tm->tm_sec);
+        buf[ABX8XX_REG_MN] = bin2bcd(tm->tm_min);
+        buf[ABX8XX_REG_HR] = bin2bcd(tm->tm_hour);
+        buf[ABX8XX_REG_DA] = bin2bcd(tm->tm_mday);
+        buf[ABX8XX_REG_MO] = bin2bcd(tm->tm_mon + 1);
+        buf[ABX8XX_REG_YR] = bin2bcd(tm->tm_year - 100);
+        buf[ABX8XX_REG_WD] = tm->tm_wday;
+
+        err = i2c_smbus_write_i2c_block_data(client, ABX8XX_REG_HTH,
+                                             sizeof(buf), buf);
+        if (err < 0) {
+                dev_err(&client->dev, "Unable to write to date registers\n");
+                return -EIO;
+        }
+
+        return 0;
+}
+
+static const struct rtc_class_ops abx80x_rtc_ops = {
+        .read_time      = abx80x_rtc_read_time,
+        .set_time       = abx80x_rtc_set_time,
+};
+
+static int abx80x_dt_trickle_cfg(struct device_node *np)
+{
+        const char *diode;
+        int