[PATCH] "RTC-framework" driver for DS1307 and similar RTC chips

This is an "RTC-framework" driver for DS1307 and similar RTC chips,

It should be a full replacement for the existing ds1337.c driver (using the
older RTC glue), giving a net increase in the number of RTC chips that work
out-of-the-box.  There's a whole cluster of RTCs that are very similar, but
the 1337 driver was a bit too picky to work with most of them.

Still no support for RTC alarm IRQs (on chips that support them).

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 407 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 875ff5e5792a..9e249650baf0 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -86,6 +86,24 @@ config RTC_DRV_X1205
           This driver can also be built as a module. If so, the module
           will be called rtc-x1205.
 
+config RTC_DRV_DS1307
+        tristate "Dallas/Maxim DS1307 and similar I2C RTC chips"
+        depends on RTC_CLASS && I2C
+        help
+          If you say yes here you get support for various compatible RTC
+          chips (often with battery backup) connected with I2C.  This driver
+          should handle DS1307, DS1337, DS1338, DS1339, DS1340, ST M41T00,
+          and probably other chips.  In some cases the RTC must already
+          have been initialized (by manufacturing or a bootloader).
+
+          The first seven registers on these chips hold an RTC, and other
+          registers may add features such as NVRAM, a trickle charger for
+          the RTC/NVRAM backup power, and alarms.  This driver may not
+          expose all those available chip features.
+
+          This driver can also be built as a module. If so, the module
+          will be called rtc-ds1307.
+
 config RTC_DRV_DS1672
         tristate "Dallas/Maxim DS1672"
         depends on RTC_CLASS && I2C
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 1b3f32ecec80..ca8bed53079f 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_RTC_INTF_DEV)	+= rtc-dev.o
 
 obj-$(CONFIG_RTC_DRV_X1205)     += rtc-x1205.o
 obj-$(CONFIG_RTC_DRV_TEST)      += rtc-test.o
+obj-$(CONFIG_RTC_DRV_DS1307)    += rtc-ds1307.o
 obj-$(CONFIG_RTC_DRV_DS1672)    += rtc-ds1672.o
 obj-$(CONFIG_RTC_DRV_PCF8563)   += rtc-pcf8563.o
 obj-$(CONFIG_RTC_DRV_RS5C372)   += rtc-rs5c372.o
diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
new file mode 100644
index 000000000000..e8afb9384786
--- /dev/null
+++ b/drivers/rtc/rtc-ds1307.c
@@ -0,0 +1,388 @@
+/*
+ * rtc-ds1307.c - RTC driver for some mostly-compatible I2C chips.
+ *
+ *  Copyright (C) 2005 James Chapman (ds1337 core)
+ *  Copyright (C) 2006 David Brownell
+ *
+ * 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/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/string.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+
+
+
+/* We can't determine type by probing, but if we expect pre-Linux code
+ * to have set the chip up as a clock (turning on the oscillator and
+ * setting the date and time), Linux can ignore the non-clock features.
+ * That's a natural job for a factory or repair bench.
+ *
+ * If the I2C "force" mechanism is used, we assume the chip is a ds1337.
+ * (Much better would be board-specific tables of I2C devices, along with
+ * the platform_data drivers would use to sort such issues out.)
+ */
+enum ds_type {
+        unknown = 0,
+        ds_1307,                /* or ds1338, ... */
+        ds_1337,                /* or ds1339, ... */
+        ds_1340,                /* or st m41t00, ... */
+        // rs5c372 too?  different address...
+};
+
+static unsigned short normal_i2c[] = { 0x68, I2C_CLIENT_END };
+
+I2C_CLIENT_INSMOD;
+
+
+
+/* RTC registers don't differ much, except for the century flag */
+#define DS1307_REG_SECS         0x00    /* 00-59 */
+#       define DS1307_BIT_CH            0x80
+#define DS1307_REG_MIN          0x01    /* 00-59 */
+#define DS1307_REG_HOUR         0x02    /* 00-23, or 1-12{am,pm} */
+#       define DS1340_BIT_CENTURY_EN    0x80    /* in REG_HOUR */
+#       define DS1340_BIT_CENTURY       0x40    /* in REG_HOUR */
+#define DS1307_REG_WDAY         0x03    /* 01-07 */
+#define DS1307_REG_MDAY         0x04    /* 01-31 */
+#define DS1307_REG_MONTH        0x05    /* 01-12 */
+#       define DS1337_BIT_CENTURY       0x80    /* in REG_MONTH */
+#define DS1307_REG_YEAR         0x06    /* 00-99 */
+
+/* Other registers (control, status, alarms, trickle charge, NVRAM, etc)
+ * start at 7, and they differ a lot. Only control and status matter for RTC;
+ * be careful using them.
+ */
+#define DS1307_REG_CONTROL      0x07
+#       define DS1307_BIT_OUT           0x80
+#       define DS1307_BIT_SQWE          0x10
+#       define DS1307_BIT_RS1           0x02
+#       define DS1307_BIT_RS0           0x01
+#define DS1337_REG_CONTROL      0x0e
+#       define DS1337_BIT_nEOSC         0x80
+#       define DS1337_BIT_RS2           0x10
+#       define DS1337_BIT_RS1           0x08
+#       define DS1337_BIT_INTCN         0x04
+#       define DS1337_BIT_A2IE          0x02
+#       define DS1337_BIT_A1IE          0x01
+#define DS1337_REG_STATUS       0x0f
+#       define DS1337_BIT_OSF           0x80
+#       define DS1337_BIT_A2I           0x02
+#       define DS1337_BIT_A1I           0x01
+#define DS1339_REG_TRICKLE      0x10
+
+
+
+struct ds1307 {
+        u8                      reg_addr;
+        u8                      regs[8];
+        enum ds_type            type;
+        struct i2c_msg          msg[2];
+        struct i2c_client       client;
+        struct rtc_device       *rtc;
+};
+
+
+static int ds1307_get_time(struct device *dev, struct rtc_time *t)
+{
+        struct ds1307   *ds1307 = dev_get_drvdata(dev);
+        int             tmp;
+
+        /* read the RTC registers all at once */
+        ds1307->msg[1].flags = I2C_M_RD;
+        ds1307->msg[1].len = 7;
+
+        tmp = i2c_transfer(ds1307->client.adapter, ds1307->msg, 2);
+        if (tmp != 2) {
+                dev_err(dev, "%s error %d\n", "read", tmp);
+                return -EIO;
+        }
+
+        dev_dbg(dev, "%s: %02x %02x %02x %02x %02x %02x %02x\n",
+                        "read",
+                        ds1307->regs[0], ds1307->regs[1],
+                        ds1307->regs[2], ds1307->regs[3],
+                        ds1307->regs[4], ds1307->regs[5],
+                        ds1307->regs[6]);
+
+        t->tm_sec = BCD2BIN(ds1307->regs[DS1307_REG_SECS] & 0x7f);
+        t->tm_min = BCD2BIN(ds1307->regs[DS1307_REG_MIN] & 0x7f);
+        tmp = ds1307->regs[DS1307_REG_HOUR] & 0x3f;
+        t->tm_hour = BCD2BIN(tmp);
+        t->tm_wday = BCD2BIN(ds1307->regs[DS1307_REG_WDAY] & 0x07) - 1;
+        t->tm_mday = BCD2BIN(ds1307->regs[DS1307_REG_MDAY] & 0x3f);
+        tmp = ds1307->regs[DS1307_REG_MONTH] & 0x1f;
+        t->tm_mon = BCD2BIN(tmp) - 1;
+
+        /* assume 20YY not 19YY, and ignore DS1337_BIT_CENTURY */
+        t->tm_year = BCD2BIN(ds1307->regs[DS1307_REG_YEAR]) + 100;
+
+        dev_dbg(dev, "%s secs=%d, mins=%d, "
+                "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
+                "read", t->tm_sec, t->tm_min,
+                t->tm_hour, t->tm_mday,
+                t->tm_mon, t->tm_year, t->tm_wday);
+
+        return 0;
+}
+
+static int ds1307_set_time(struct device *dev, struct rtc_time *t)
+{
+        struct ds1307   *ds1307 = dev_get_drvdata(dev);
+        int             result;
+        int             tmp;
+        u8              *buf = ds1307->regs;
+
+        dev_dbg(dev, "%s secs=%d, mins=%d, "
+                "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
+                "write", dt->tm_sec, dt->tm_min,
+                dt->tm_hour, dt->tm_mday,
+                dt->tm_mon, dt->tm_year, dt->tm_wday);
+
+        *buf++ = 0;             /* first register addr */
+        buf[DS1307_REG_SECS] = BIN2BCD(t->tm_sec);
+        buf[DS1307_REG_MIN] = BIN2BCD(t->tm_min);
+        buf[DS1307_REG_HOUR] = BIN2BCD(t->tm_hour);
+        buf[DS1307_REG_WDAY] = BIN2BCD(t->tm_wday + 1);
+        buf[DS1307_REG_MDAY] = BIN2BCD(t->tm_mday);
+        buf[DS1307_REG_MONTH] = BIN2BCD(t->tm_mon + 1);
+
+        /* assume 20YY not 19YY */
+        tmp = t->tm_year - 100;
+        buf[DS1307_REG_YEAR] = BIN2BCD(tmp);
+
+        if (ds1307->type == ds_1337)
+                buf[DS1307_REG_MONTH] |= DS1337_BIT_CENTURY;
+        else if (ds1307->type == ds_1340)
+                buf[DS1307_REG_HOUR] |= DS1340_BIT_CENTURY_EN
+                                | DS1340_BIT_CENTURY;
+
+        ds1307->msg[1].flags = 0;
+        ds1307->msg[1].len = 8;
+
+        dev_dbg(dev, "%s: %02x %02x %02x %02x %02x %02x %02x\n",
+                "write", buf[0], buf[1], buf[2], buf[3],
+                buf[4], buf[5], buf[6]);
+
+        result = i2c_transfer(ds1307->client.adapter, &ds1307->msg[1], 1);
+        if (result != 1) {
+                dev_err(dev, "%s error %d\n", "write", tmp);
+                return -EIO;
+        }
+        return 0;
+}
+
+static struct rtc_class_ops ds13xx_rtc_ops = {
+        .read_time      = ds1307_get_time,
+        .set_time       = ds1307_set_time,
+};
+
+static struct i2c_driver ds1307_driver;
+
+static int __devinit
+ds1307_detect(struct i2c_adapter *adapter, int address, int kind)
+{
+        struct ds1307           *ds1307;
+        int                     err = -ENODEV;
+        struct i2c_client       *client;
+        int                     tmp;
+
+        if (!(ds1307 = kzalloc(sizeof(struct ds1307), GFP_KERNEL))) {
+                err = -ENOMEM;
+                goto exit;
+        }
+
+        client = &ds1307->client;
+        client->addr = address;
+        client->adapter = adapter;
+        client->driver = &ds1307_driver;
+        client->flags = 0;
+
+        i2c_set_clientdata(client, ds1307);
+
+        ds1307->msg[0].addr = client->addr;
+        ds1307->msg[0].flags = 0;
+        ds1307->msg[0].len = 1;
+        ds1307->msg[0].buf = &ds1307->reg_addr;
+
+        ds1307->msg[1].addr = client->addr;
+        ds1307->msg[1].flags = I2C_M_RD;
+        ds1307->msg[1].len = sizeof(ds1307->regs);
+        ds1307->msg[1].buf = ds1307->regs;
+
+        /* HACK: "force" implies "needs ds1337-style-oscillator setup" */
+        if (kind >= 0) {
+                ds1307->type = ds_1337;
+
+                ds1307->reg_addr = DS1337_REG_CONTROL;
+                ds1307->msg[1].len = 2;
+
+                tmp = i2c_transfer(client->adapter, ds1307->msg, 2);
+                if (tmp != 2) {
+                        pr_debug("read error %d\n", tmp);
+                        err = -EIO;
+                        goto exit_free;
+                }
+
+                ds1307->reg_addr = 0;
+                ds1307->msg[1].len = sizeof(ds1307->regs);
+
+                /* oscillator is off; need to turn it on */
+                if ((ds1307->regs[0] & DS1337_BIT_nEOSC)
+                                || (ds1307->regs[1] & DS1337_BIT_OSF)) {
+                        printk(KERN_ERR "no ds1337 oscillator code\n");
+                        goto exit_free;
+                }
+        } else
+                ds1307->type = ds_1307;
+
+read_rtc:
+        /* read RTC registers */
+
+        tmp = i2c_transfer(client->adapter, ds1307->msg, 2);
+        if (tmp != 2) {
+                pr_debug("read error %d\n", tmp);
+                err = -EIO;
+                goto exit_free;
+        }
+
+        /* minimal sanity checking; some chips (like DS1340) don't
+         * specify the extra bits as must-be-zero, but there are
+         * still a few values that are clearly out-of-range.
+         */
+        tmp = ds1307->regs[DS1307_REG_SECS];
+        if (tmp & DS1307_BIT_CH) {
+                if (ds1307->type && ds1307->type != ds_1307) {
+                        pr_debug("not a ds1307?\n");
+                        goto exit_free;
+                }
+                ds1307->type = ds_1307;
+
+                /* this partial initialization should work for ds1307,
+                 * ds1338, ds1340, st m41t00, and more.
+                 */
+                dev_warn(&client->dev, "oscillator started; SET TIME!\n");
+                i2c_smbus_write_byte_data(client, 0, 0);
+                goto read_rtc;
+        }
+        tmp = BCD2BIN(tmp & 0x7f);
+        if (tmp > 60)
+                goto exit_free;
+        tmp = BCD2BIN(ds1307->regs[DS1307_REG_MIN] & 0x7f);
+        if (tmp > 60)
+                goto exit_free;
+
+        tmp = BCD2BIN(ds1307->regs[DS1307_REG_MDAY] & 0x3f);
+        if (tmp == 0 || tmp > 31)
+                goto exit_free;
+
+        tmp = BCD2BIN(ds1307->regs[DS1307_REG_MONTH] & 0x1f);
+        if (tmp == 0 || tmp > 12)
+                goto exit_free;
+
+        /* force into in 24 hour mode (most chips) or
+         * disable century bit (ds1340)
+         */
+        tmp = ds1307->regs[DS1307_REG_HOUR];
+        if (tmp & (1 << 6)) {
+                if (tmp & (1 << 5))
+                        tmp = BCD2BIN(tmp & 0x1f) + 12;
+                else
+                        tmp = BCD2BIN(tmp);
+                i2c_smbus_write_byte_data(client,
+                                DS1307_REG_HOUR,
+                                BIN2BCD(tmp));
+        }
+
+        /* FIXME chips like 1337 can generate alarm irqs too; those are
+         * worth exposing through the API (especially when the irq is
+         * wakeup-capable).
+         */
+
+        switch (ds1307->type) {
+        case unknown:
+                strlcpy(client->name, "unknown", I2C_NAME_SIZE);
+                break;
+        case ds_1307:
+                strlcpy(client->name, "ds1307", I2C_NAME_SIZE);
+                break;
+        case ds_1337:
+                strlcpy(client->name, "ds1337", I2C_NAME_SIZE);
+                break;
+        case ds_1340:
+                strlcpy(client->name, "ds1340", I2C_NAME_SIZE);
+                break;
+        }
+
+        /* Tell the I2C layer a new client has arrived */
+        if ((err = i2c_attach_client(client)))
+                goto exit_free;
+
+        ds1307->rtc = rtc_device_register(client->name, &client->dev,
+                                &ds13xx_rtc_ops, THIS_MODULE);
+        if (IS_ERR(ds1307->rtc)) {
+                err = PTR_ERR(ds1307->rtc);
+                dev_err(&client->dev,
+                        "unable to register the class device\n");
+                goto exit_detach;
+        }
+
+        return 0;
+
+exit_detach:
+        i2c_detach_client(client);
+exit_free:
+        kfree(ds1307);
+exit:
+        return err;
+}
+
+static int __devinit
+ds1307_attach_adapter(struct i2c_adapter *adapter)
+{
+        if (!i2c_check_functionality(adapter, I2C_FUNC_I2C))
+                return 0;
+        return i2c_probe(adapter, &addr_data, ds1307_detect);
+}
+
+static int __devexit ds1307_detach_client(struct i2c_client *client)
+{
+        int             err;
+        struct ds1307   *ds1307 = i2c_get_clientdata(client);
+
+        rtc_device_unregister(ds1307->rtc);
+        if ((err = i2c_detach_client(client)))
+                return err;
+        kfree(ds1307);
+        return 0;
+}
+
+static struct i2c_driver ds1307_driver = {
+        .driver = {
+                .name   = "ds1307",
+                .owner  = THIS_MODULE,
+        },
+        .attach_adapter = ds1307_attach_adapter,
+        .detach_client  = __devexit_p(ds1307_detach_client),
+};
+
+static int __init ds1307_init(void)
+{
+        return i2c_add_driver(&ds1307_driver);
+}
+module_init(ds1307_init);
+
+static void __exit ds1307_exit(void)
+{
+        i2c_del_driver(&ds1307_driver);
+}
+module_exit(ds1307_exit);
+
+MODULE_DESCRIPTION("RTC driver for DS1307 and similar chips");
+MODULE_LICENSE("GPL");