[PATCH] I2C: Add support for Maxim/Dallas DS1374 Real-Time Clock Chip (1/2)

Add support for Maxim/Dallas DS1374 Real-Time Clock Chip

This change adds support for the Maxim/Dallas DS1374 RTC chip. This chip
is an I2C-based RTC that maintains a simple 32-bit binary seconds count
with battery backup support.

Signed-off-by: Randy Vinson <rvinson@mvista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 266 insertions, 0 deletions

diff --git a/drivers/i2c/chips/ds1374.c b/drivers/i2c/chips/ds1374.c
new file mode 100644
index 000000000000..1278d979db2b
--- /dev/null
+++ b/drivers/i2c/chips/ds1374.c
@@ -0,0 +1,266 @@
+/*
+ * drivers/i2c/chips/ds1374.c
+ *
+ * I2C client/driver for the Maxim/Dallas DS1374 Real-Time Clock
+ *
+ * Author: Randy Vinson <rvinson@mvista.com>
+ *
+ * Based on the m41t00.c by Mark Greer <mgreer@mvista.com>
+ *
+ * 2005 (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.
+ */
+/*
+ * This i2c client/driver wedges between the drivers/char/genrtc.c RTC
+ * interface and the SMBus interface of the i2c subsystem.
+ * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
+ * recommened in .../Documentation/i2c/writing-clients section
+ * "Sending and receiving", using SMBus level communication is preferred.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/i2c.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+
+#include <asm/time.h>
+#include <asm/rtc.h>
+
+#define DS1374_REG_TOD0         0x00
+#define DS1374_REG_TOD1         0x01
+#define DS1374_REG_TOD2         0x02
+#define DS1374_REG_TOD3         0x03
+#define DS1374_REG_WDALM0       0x04
+#define DS1374_REG_WDALM1       0x05
+#define DS1374_REG_WDALM2       0x06
+#define DS1374_REG_CR           0x07
+#define DS1374_REG_SR           0x08
+#define DS1374_REG_SR_OSF       0x80
+#define DS1374_REG_TCR          0x09
+
+#define DS1374_DRV_NAME         "ds1374"
+
+static DECLARE_MUTEX(ds1374_mutex);
+
+static struct i2c_driver ds1374_driver;
+static struct i2c_client *save_client;
+
+static unsigned short ignore[] = { I2C_CLIENT_END };
+static unsigned short normal_addr[] = { 0x68, I2C_CLIENT_END };
+
+static struct i2c_client_address_data addr_data = {
+        .normal_i2c = normal_addr,
+        .normal_i2c_range = ignore,
+        .probe = ignore,
+        .probe_range = ignore,
+        .ignore = ignore,
+        .ignore_range = ignore,
+        .force = ignore,
+};
+
+static ulong ds1374_read_rtc(void)
+{
+        ulong time = 0;
+        int reg = DS1374_REG_WDALM0;
+
+        while (reg--) {
+                s32 tmp;
+                if ((tmp = i2c_smbus_read_byte_data(save_client, reg)) < 0) {
+                        dev_warn(&save_client->dev,
+                                 "can't read from rtc chip\n");
+                        return 0;
+                }
+                time = (time << 8) | (tmp & 0xff);
+        }
+        return time;
+}
+
+static void ds1374_write_rtc(ulong time)
+{
+        int reg;
+
+        for (reg = DS1374_REG_TOD0; reg < DS1374_REG_WDALM0; reg++) {
+                if (i2c_smbus_write_byte_data(save_client, reg, time & 0xff)
+                    < 0) {
+                        dev_warn(&save_client->dev,
+                                 "can't write to rtc chip\n");
+                        break;
+                }
+                time = time >> 8;
+        }
+}
+
+static void ds1374_check_rtc_status(void)
+{
+        s32 tmp;
+
+        tmp = i2c_smbus_read_byte_data(save_client, DS1374_REG_SR);
+        if (tmp < 0) {
+                dev_warn(&save_client->dev,
+                         "can't read status from rtc chip\n");
+                return;
+        }
+        if (tmp & DS1374_REG_SR_OSF) {
+                dev_warn(&save_client->dev,
+                         "oscillator discontinuity flagged, time unreliable\n");
+                tmp &= ~DS1374_REG_SR_OSF;
+                tmp = i2c_smbus_write_byte_data(save_client, DS1374_REG_SR,
+                                                tmp & 0xff);
+                if (tmp < 0)
+                        dev_warn(&save_client->dev,
+                                 "can't clear discontinuity notification\n");
+        }
+}
+
+ulong ds1374_get_rtc_time(void)
+{
+        ulong t1, t2;
+        int limit = 10;         /* arbitrary retry limit */
+
+        down(&ds1374_mutex);
+
+        /*
+         * Since the reads are being performed one byte at a time using
+         * the SMBus vs a 4-byte i2c transfer, there is a chance that a
+         * carry will occur during the read. To detect this, 2 reads are
+         * performed and compared.
+         */
+        do {
+                t1 = ds1374_read_rtc();
+                t2 = ds1374_read_rtc();
+        } while (t1 != t2 && limit--);
+
+        up(&ds1374_mutex);
+
+        if (t1 != t2) {
+                dev_warn(&save_client->dev,
+                         "can't get consistent time from rtc chip\n");
+                t1 = 0;
+        }
+
+        return t1;
+}
+
+static void ds1374_set_tlet(ulong arg)
+{
+        ulong t1, t2;
+        int limit = 10;         /* arbitrary retry limit */
+
+        t1 = *(ulong *) arg;
+
+        down(&ds1374_mutex);
+
+        /*
+         * Since the writes are being performed one byte at a time using
+         * the SMBus vs a 4-byte i2c transfer, there is a chance that a
+         * carry will occur during the write. To detect this, the write
+         * value is read back and compared.
+         */
+        do {
+                ds1374_write_rtc(t1);
+                t2 = ds1374_read_rtc();
+        } while (t1 != t2 && limit--);
+
+        up(&ds1374_mutex);
+
+        if (t1 != t2)
+                dev_warn(&save_client->dev,
+                         "can't confirm time set from rtc chip\n");
+}
+
+ulong new_time;
+
+DECLARE_TASKLET_DISABLED(ds1374_tasklet, ds1374_set_tlet, (ulong) & new_time);
+
+int ds1374_set_rtc_time(ulong nowtime)
+{
+        new_time = nowtime;
+
+        if (in_interrupt())
+                tasklet_schedule(&ds1374_tasklet);
+        else
+                ds1374_set_tlet((ulong) & new_time);
+
+        return 0;
+}
+
+/*
+ *****************************************************************************
+ *
+ *      Driver Interface
+ *
+ *****************************************************************************
+ */
+static int ds1374_probe(struct i2c_adapter *adap, int addr, int kind)
+{
+        struct i2c_client *client;
+        int rc;
+
+        client = kmalloc(sizeof(struct i2c_client), GFP_KERNEL);
+        if (!client)
+                return -ENOMEM;
+
+        memset(client, 0, sizeof(struct i2c_client));
+        strncpy(client->name, DS1374_DRV_NAME, I2C_NAME_SIZE);
+        client->flags = I2C_DF_NOTIFY;
+        client->addr = addr;
+        client->adapter = adap;
+        client->driver = &ds1374_driver;
+
+        if ((rc = i2c_attach_client(client)) != 0) {
+                kfree(client);
+                return rc;
+        }
+
+        save_client = client;
+
+        ds1374_check_rtc_status();
+
+        return 0;
+}
+
+static int ds1374_attach(struct i2c_adapter *adap)
+{
+        return i2c_probe(adap, &addr_data, ds1374_probe);
+}
+
+static int ds1374_detach(struct i2c_client *client)
+{
+        int rc;
+
+        if ((rc = i2c_detach_client(client)) == 0) {
+                kfree(i2c_get_clientdata(client));
+                tasklet_kill(&ds1374_tasklet);
+        }
+        return rc;
+}
+
+static struct i2c_driver ds1374_driver = {
+        .owner = THIS_MODULE,
+        .name = DS1374_DRV_NAME,
+        .id = I2C_DRIVERID_DS1374,
+        .flags = I2C_DF_NOTIFY,
+        .attach_adapter = ds1374_attach,
+        .detach_client = ds1374_detach,
+};
+
+static int __init ds1374_init(void)
+{
+        return i2c_add_driver(&ds1374_driver);
+}
+
+static void __exit ds1374_exit(void)
+{
+        i2c_del_driver(&ds1374_driver);
+}
+
+module_init(ds1374_init);
+module_exit(ds1374_exit);
+
+MODULE_AUTHOR("Randy Vinson <rvinson@mvista.com>");
+MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC I2C Client Driver");
+MODULE_LICENSE("GPL");