rtc: add RTC class driver for the Maxim MAX6900

Signed-off-by: Dale Farnsworth.org <dale@farnsworth.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 322 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 372d74963dd4..1b853c4ff86d 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -334,6 +334,16 @@ config RTC_DRV_TEST
           This driver can also be built as a module. If so, the module
           will be called rtc-test.
 
+config RTC_DRV_MAX6900
+        tristate "Maxim 6900"
+        depends on RTC_CLASS && I2C
+        help
+          If you say yes here you will get support for the
+          Maxim MAX6900 I2C RTC chip.
+
+          This driver can also be built as a module. If so, the module
+          will be called rtc-max6900.
+
 config RTC_DRV_MAX6902
         tristate "Maxim 6902"
         depends on RTC_CLASS && SPI
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index cad027d36447..f9a3e0130f4e 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_RTC_DRV_EP93XX)	+= rtc-ep93xx.o
 obj-$(CONFIG_RTC_DRV_SA1100)    += rtc-sa1100.o
 obj-$(CONFIG_RTC_DRV_VR41XX)    += rtc-vr41xx.o
 obj-$(CONFIG_RTC_DRV_PL031)     += rtc-pl031.o
+obj-$(CONFIG_RTC_DRV_MAX6900)   += rtc-max6900.o
 obj-$(CONFIG_RTC_DRV_MAX6902)   += rtc-max6902.o
 obj-$(CONFIG_RTC_DRV_V3020)     += rtc-v3020.o
 obj-$(CONFIG_RTC_DRV_AT91RM9200)+= rtc-at91rm9200.o
diff --git a/drivers/rtc/rtc-max6900.c b/drivers/rtc/rtc-max6900.c
new file mode 100644
index 000000000000..eee4ee5bb75a
--- /dev/null
+++ b/drivers/rtc/rtc-max6900.c
@@ -0,0 +1,311 @@
+/*
+ * rtc class driver for the Maxim MAX6900 chip
+ *
+ * Author: Dale Farnsworth <dale@farnsworth.org>
+ *
+ * based on previously existing rtc class drivers
+ *
+ * 2007 (c) MontaVista, Software, Inc.  This file is licensed under
+ * the terms of the GNU General Public License version 2.  This program
+ * is licensed "as is" without any warranty of any kind, whether express
+ * or implied.
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/bcd.h>
+#include <linux/rtc.h>
+#include <linux/delay.h>
+
+#define DRV_NAME "max6900"
+#define DRV_VERSION "0.1"
+
+/*
+ * register indices
+ */
+#define MAX6900_REG_SC                  0       /* seconds      00-59 */
+#define MAX6900_REG_MN                  1       /* minutes      00-59 */
+#define MAX6900_REG_HR                  2       /* hours        00-23 */
+#define MAX6900_REG_DT                  3       /* day of month 00-31 */
+#define MAX6900_REG_MO                  4       /* month        01-12 */
+#define MAX6900_REG_DW                  5       /* day of week   1-7  */
+#define MAX6900_REG_YR                  6       /* year         00-99 */
+#define MAX6900_REG_CT                  7       /* control */
+#define MAX6900_REG_LEN                 8
+
+#define MAX6900_REG_CT_WP               (1 << 7)        /* Write Protect */
+
+/*
+ * register read/write commands
+ */
+#define MAX6900_REG_CONTROL_WRITE       0x8e
+#define MAX6900_REG_BURST_READ          0xbf
+#define MAX6900_REG_BURST_WRITE         0xbe
+#define MAX6900_REG_RESERVED_READ       0x96
+
+#define MAX6900_IDLE_TIME_AFTER_WRITE   3       /* specification says 2.5 mS */
+
+#define MAX6900_I2C_ADDR                0xa0
+
+static unsigned short normal_i2c[] = {
+        MAX6900_I2C_ADDR >> 1,
+        I2C_CLIENT_END
+};
+
+I2C_CLIENT_INSMOD;                      /* defines addr_data */
+
+static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind);
+
+static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
+{
+        u8 reg_addr[1] = { MAX6900_REG_BURST_READ };
+        struct i2c_msg msgs[2] = {
+                {
+                        .addr   = client->addr,
+                        .flags  = 0, /* write */
+                        .len    = sizeof(reg_addr),
+                        .buf    = reg_addr
+                },
+                {
+                        .addr   = client->addr,
+                        .flags  = I2C_M_RD,
+                        .len    = MAX6900_REG_LEN,
+                        .buf    = buf
+                }
+        };
+        int rc;
+
+        rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+        if (rc != ARRAY_SIZE(msgs)) {
+                dev_err(&client->dev, "%s: register read failed\n",
+                        __FUNCTION__);
+                return -EIO;
+        }
+        return 0;
+}
+
+static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
+{
+        u8 i2c_buf[MAX6900_REG_LEN + 1] = { MAX6900_REG_BURST_WRITE };
+        struct i2c_msg msgs[1] = {
+                {
+                        .addr   = client->addr,
+                        .flags  = 0, /* write */
+                        .len    = MAX6900_REG_LEN + 1,
+                        .buf    = i2c_buf
+                }
+        };
+        int rc;
+
+        memcpy(&i2c_buf[1], buf, MAX6900_REG_LEN);
+
+        rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+        if (rc != ARRAY_SIZE(msgs)) {
+                dev_err(&client->dev, "%s: register write failed\n",
+                        __FUNCTION__);
+                return -EIO;
+        }
+        msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
+        return 0;
+}
+
+static int max6900_i2c_validate_client(struct i2c_client *client)
+{
+        u8 regs[MAX6900_REG_LEN];
+        u8 zero_mask[MAX6900_REG_LEN] = {
+                0x80,   /* seconds */
+                0x80,   /* minutes */
+                0x40,   /* hours */
+                0xc0,   /* day of month */
+                0xe0,   /* month */
+                0xf8,   /* day of week */
+                0x00,   /* year */
+                0x7f,   /* control */
+        };
+        int i;
+        int rc;
+        int reserved;
+
+        reserved = i2c_smbus_read_byte_data(client, MAX6900_REG_RESERVED_READ);
+        if (reserved != 0x07)
+                return -ENODEV;
+
+        rc = max6900_i2c_read_regs(client, regs);
+        if (rc < 0)
+                return rc;
+
+        for (i = 0; i < MAX6900_REG_LEN; ++i) {
+                if (regs[i] & zero_mask[i])
+                        return -ENODEV;
+        }
+
+        return 0;
+}
+
+static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
+{
+        int rc;
+        u8 regs[MAX6900_REG_LEN];
+
+        rc = max6900_i2c_read_regs(client, regs);
+        if (rc < 0)
+                return rc;
+
+        tm->tm_sec = BCD2BIN(regs[MAX6900_REG_SC]);
+        tm->tm_min = BCD2BIN(regs[MAX6900_REG_MN]);
+        tm->tm_hour = BCD2BIN(regs[MAX6900_REG_HR] & 0x3f);
+        tm->tm_mday = BCD2BIN(regs[MAX6900_REG_DT]);
+        tm->tm_mon = BCD2BIN(regs[MAX6900_REG_MO]) - 1;
+        tm->tm_year = BCD2BIN(regs[MAX6900_REG_YR]) + 100;
+        tm->tm_wday = BCD2BIN(regs[MAX6900_REG_DW]);
+
+        return 0;
+}
+
+static int max6900_i2c_clear_write_protect(struct i2c_client *client)
+{
+        int rc;
+        rc = i2c_smbus_write_byte_data (client, MAX6900_REG_CONTROL_WRITE, 0);
+        if (rc < 0) {
+                dev_err(&client->dev, "%s: control register write failed\n",
+                        __FUNCTION__);
+                return -EIO;
+        }
+        return 0;
+}
+
+static int max6900_i2c_set_time(struct i2c_client *client,
+                                struct rtc_time const *tm)
+{
+        u8 regs[MAX6900_REG_LEN];
+        int rc;
+
+        rc = max6900_i2c_clear_write_protect(client);
+        if (rc < 0)
+                return rc;
+
+        regs[MAX6900_REG_SC] = BIN2BCD(tm->tm_sec);
+        regs[MAX6900_REG_MN] = BIN2BCD(tm->tm_min);
+        regs[MAX6900_REG_HR] = BIN2BCD(tm->tm_hour);
+        regs[MAX6900_REG_DT] = BIN2BCD(tm->tm_mday);
+        regs[MAX6900_REG_MO] = BIN2BCD(tm->tm_mon + 1);
+        regs[MAX6900_REG_YR] = BIN2BCD(tm->tm_year - 100);
+        regs[MAX6900_REG_DW] = BIN2BCD(tm->tm_wday);
+        regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;       /* set write protect */
+
+        rc = max6900_i2c_write_regs(client, regs);
+        if (rc < 0)
+                return rc;
+
+        return 0;
+}
+
+static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+        return max6900_i2c_read_time(to_i2c_client(dev), tm);
+}
+
+static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+        return max6900_i2c_set_time(to_i2c_client(dev), tm);
+}
+
+static int max6900_attach_adapter(struct i2c_adapter *adapter)
+{
+        return i2c_probe(adapter, &addr_data, max6900_probe);
+}
+
+static int max6900_detach_client(struct i2c_client *client)
+{
+        struct rtc_device *const rtc = i2c_get_clientdata(client);
+
+        if (rtc)
+                rtc_device_unregister(rtc);
+
+        return i2c_detach_client(client);
+}
+
+static struct i2c_driver max6900_driver = {
+        .driver         = {
+                .name   = DRV_NAME,
+        },
+        .id             = I2C_DRIVERID_MAX6900,
+        .attach_adapter = max6900_attach_adapter,
+        .detach_client  = max6900_detach_client,
+};
+
+static const struct rtc_class_ops max6900_rtc_ops = {
+        .read_time      = max6900_rtc_read_time,
+        .set_time       = max6900_rtc_set_time,
+};
+
+static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind)
+{
+        int rc = 0;
+        struct i2c_client *client = NULL;
+        struct rtc_device *rtc = NULL;
+
+        if (!i2c_check_functionality(adapter, I2C_FUNC_I2C)) {
+                rc = -ENODEV;
+                goto failout;
+        }
+
+        client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
+        if (client == NULL) {
+                rc = -ENOMEM;
+                goto failout;
+        }
+
+        client->addr = addr;
+        client->adapter = adapter;
+        client->driver = &max6900_driver;
+        strlcpy(client->name, DRV_NAME, I2C_NAME_SIZE);
+
+        if (kind < 0) {
+                rc = max6900_i2c_validate_client(client);
+                if (rc < 0)
+                        goto failout;
+        }
+
+        rc = i2c_attach_client(client);
+        if (rc < 0)
+                goto failout;
+
+        dev_info(&client->dev,
+                 "chip found, driver version " DRV_VERSION "\n");
+
+        rtc = rtc_device_register(max6900_driver.driver.name,
+                                  &client->dev,
+                                  &max6900_rtc_ops, THIS_MODULE);
+        if (IS_ERR(rtc)) {
+                rc = PTR_ERR(rtc);
+                goto failout_detach;
+        }
+
+        i2c_set_clientdata(client, rtc);
+
+        return 0;
+
+failout_detach:
+        i2c_detach_client(client);
+failout:
+        kfree(client);
+        return rc;
+}
+
+static int __init max6900_init(void)
+{
+        return i2c_add_driver(&max6900_driver);
+}
+
+static void __exit max6900_exit(void)
+{
+        i2c_del_driver(&max6900_driver);
+}
+
+MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(DRV_VERSION);
+
+module_init(max6900_init);
+module_exit(max6900_exit);