rtc: watchdog support for rtc-m41t80 driver

Add a watchdog driver interface to rtc-m41t80 driver.  This is derived from
works by Alexander Bigga <ab@mycable.de>

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Alexander Bigga <ab@mycable.de>
Cc: David Brownell <david-b@pacbell.net>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 295 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index fb9ce745cd30..359323378c55 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -224,6 +224,13 @@ config RTC_DRV_M41T80
           This driver can also be built as a module. If so, the module
           will be called rtc-m41t80.
 
+config RTC_DRV_M41T80_WDT
+        bool "ST M41T80 series RTC watchdog timer"
+        depends on RTC_DRV_M41T80
+        help
+          If you say Y here you will get support for the
+          watchdog timer in ST M41T80 RTC chips series.
+
 comment "SPI RTC drivers"
         depends on RTC_CLASS && SPI_MASTER
 
diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c
index 4875a4444216..80c4a8463065 100644
--- a/drivers/rtc/rtc-m41t80.c
+++ b/drivers/rtc/rtc-m41t80.c
@@ -20,6 +20,13 @@
 #include <linux/i2c.h>
 #include <linux/rtc.h>
 #include <linux/bcd.h>
+#ifdef CONFIG_RTC_DRV_M41T80_WDT
+#include <linux/miscdevice.h>
+#include <linux/watchdog.h>
+#include <linux/reboot.h>
+#include <linux/fs.h>
+#include <linux/ioctl.h>
+#endif
 
 #define M41T80_REG_SSEC 0
 #define M41T80_REG_SEC  1
@@ -480,6 +487,268 @@ static int m41t80_sysfs_register(struct device *dev)
 }
 #endif
 
+#ifdef CONFIG_RTC_DRV_M41T80_WDT
+/*
+ *****************************************************************************
+ *
+ * Watchdog Driver
+ *
+ *****************************************************************************
+ */
+static struct i2c_client *save_client;
+
+/* Default margin */
+#define WD_TIMO 60              /* 1..31 seconds */
+
+static int wdt_margin = WD_TIMO;
+module_param(wdt_margin, int, 0);
+MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 60s)");
+
+static unsigned long wdt_is_open;
+static int boot_flag;
+
+/**
+ *      wdt_ping:
+ *
+ *      Reload counter one with the watchdog timeout. We don't bother reloading
+ *      the cascade counter.
+ */
+static void wdt_ping(void)
+{
+        unsigned char i2c_data[2];
+        struct i2c_msg msgs1[1] = {
+                {
+                        .addr   = save_client->addr,
+                        .flags  = 0,
+                        .len    = 2,
+                        .buf    = i2c_data,
+                },
+        };
+        i2c_data[0] = 0x09;             /* watchdog register */
+
+        if (wdt_margin > 31)
+                i2c_data[1] = (wdt_margin & 0xFC) | 0x83; /* resolution = 4s */
+        else
+                /*
+                 * WDS = 1 (0x80), mulitplier = WD_TIMO, resolution = 1s (0x02)
+                 */
+                i2c_data[1] = wdt_margin<<2 | 0x82;
+
+        i2c_transfer(save_client->adapter, msgs1, 1);
+}
+
+/**
+ *      wdt_disable:
+ *
+ *      disables watchdog.
+ */
+static void wdt_disable(void)
+{
+        unsigned char i2c_data[2], i2c_buf[0x10];
+        struct i2c_msg msgs0[2] = {
+                {
+                        .addr   = save_client->addr,
+                        .flags  = 0,
+                        .len    = 1,
+                        .buf    = i2c_data,
+                },
+                {
+                        .addr   = save_client->addr,
+                        .flags  = I2C_M_RD,
+                        .len    = 1,
+                        .buf    = i2c_buf,
+                },
+        };
+        struct i2c_msg msgs1[1] = {
+                {
+                        .addr   = save_client->addr,
+                        .flags  = 0,
+                        .len    = 2,
+                        .buf    = i2c_data,
+                },
+        };
+
+        i2c_data[0] = 0x09;
+        i2c_transfer(save_client->adapter, msgs0, 2);
+
+        i2c_data[0] = 0x09;
+        i2c_data[1] = 0x00;
+        i2c_transfer(save_client->adapter, msgs1, 1);
+}
+
+/**
+ *      wdt_write:
+ *      @file: file handle to the watchdog
+ *      @buf: buffer to write (unused as data does not matter here
+ *      @count: count of bytes
+ *      @ppos: pointer to the position to write. No seeks allowed
+ *
+ *      A write to a watchdog device is defined as a keepalive signal. Any
+ *      write of data will do, as we we don't define content meaning.
+ */
+static ssize_t wdt_write(struct file *file, const char __user *buf,
+                         size_t count, loff_t *ppos)
+{
+        /*  Can't seek (pwrite) on this device
+        if (ppos != &file->f_pos)
+        return -ESPIPE;
+        */
+        if (count) {
+                wdt_ping();
+                return 1;
+        }
+        return 0;
+}
+
+static ssize_t wdt_read(struct file *file, char __user *buf,
+                        size_t count, loff_t *ppos)
+{
+        return 0;
+}
+
+/**
+ *      wdt_ioctl:
+ *      @inode: inode of the device
+ *      @file: file handle to the device
+ *      @cmd: watchdog command
+ *      @arg: argument pointer
+ *
+ *      The watchdog API defines a common set of functions for all watchdogs
+ *      according to their available features. We only actually usefully support
+ *      querying capabilities and current status.
+ */
+static int wdt_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
+                     unsigned long arg)
+{
+        int new_margin, rv;
+        static struct watchdog_info ident = {
+                .options = WDIOF_POWERUNDER | WDIOF_KEEPALIVEPING |
+                        WDIOF_SETTIMEOUT,
+                .firmware_version = 1,
+                .identity = "M41T80 WTD"
+        };
+
+        switch (cmd) {
+        case WDIOC_GETSUPPORT:
+                return copy_to_user((struct watchdog_info __user *)arg, &ident,
+                                    sizeof(ident)) ? -EFAULT : 0;
+
+        case WDIOC_GETSTATUS:
+        case WDIOC_GETBOOTSTATUS:
+                return put_user(boot_flag, (int __user *)arg);
+        case WDIOC_KEEPALIVE:
+                wdt_ping();
+                return 0;
+        case WDIOC_SETTIMEOUT:
+                if (get_user(new_margin, (int __user *)arg))
+                        return -EFAULT;
+                /* Arbitrary, can't find the card's limits */
+                if (new_margin < 1 || new_margin > 124)
+                        return -EINVAL;
+                wdt_margin = new_margin;
+                wdt_ping();
+                /* Fall */
+        case WDIOC_GETTIMEOUT:
+                return put_user(wdt_margin, (int __user *)arg);
+
+        case WDIOC_SETOPTIONS:
+                if (copy_from_user(&rv, (int __user *)arg, sizeof(int)))
+                        return -EFAULT;
+
+                if (rv & WDIOS_DISABLECARD) {
+                        printk(KERN_INFO
+                               "rtc-m41t80: disable watchdog\n");
+                        wdt_disable();
+                }
+
+                if (rv & WDIOS_ENABLECARD) {
+                        printk(KERN_INFO
+                               "rtc-m41t80: enable watchdog\n");
+                        wdt_ping();
+                }
+
+                return -EINVAL;
+        }
+        return -ENOTTY;
+}
+
+/**
+ *      wdt_open:
+ *      @inode: inode of device
+ *      @file: file handle to device
+ *
+ */
+static int wdt_open(struct inode *inode, struct file *file)
+{
+        if (MINOR(inode->i_rdev) == WATCHDOG_MINOR) {
+                if (test_and_set_bit(0, &wdt_is_open))
+                        return -EBUSY;
+                /*
+                 *      Activate
+                 */
+                wdt_is_open = 1;
+                return 0;
+        }
+        return -ENODEV;
+}
+
+/**
+ *      wdt_close:
+ *      @inode: inode to board
+ *      @file: file handle to board
+ *
+ */
+static int wdt_release(struct inode *inode, struct file *file)
+{
+        if (MINOR(inode->i_rdev) == WATCHDOG_MINOR)
+                clear_bit(0, &wdt_is_open);
+        return 0;
+}
+
+/**
+ *      notify_sys:
+ *      @this: our notifier block
+ *      @code: the event being reported
+ *      @unused: unused
+ *
+ *      Our notifier is called on system shutdowns. We want to turn the card
+ *      off at reboot otherwise the machine will reboot again during memory
+ *      test or worse yet during the following fsck. This would suck, in fact
+ *      trust me - if it happens it does suck.
+ */
+static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
+                          void *unused)
+{
+        if (code == SYS_DOWN || code == SYS_HALT)
+                /* Disable Watchdog */
+                wdt_disable();
+        return NOTIFY_DONE;
+}
+
+static const struct file_operations wdt_fops = {
+        .owner  = THIS_MODULE,
+        .read   = wdt_read,
+        .ioctl  = wdt_ioctl,
+        .write  = wdt_write,
+        .open   = wdt_open,
+        .release = wdt_release,
+};
+
+static struct miscdevice wdt_dev = {
+        .minor = WATCHDOG_MINOR,
+        .name = "watchdog",
+        .fops = &wdt_fops,
+};
+
+/*
+ *      The WDT card needs to learn about soft shutdowns in order to
+ *      turn the timebomb registers off.
+ */
+static struct notifier_block wdt_notifier = {
+        .notifier_call = wdt_notify_sys,
+};
+#endif /* CONFIG_RTC_DRV_M41T80_WDT */
+
 /*
  *****************************************************************************
  *
@@ -572,6 +841,19 @@ static int m41t80_probe(struct i2c_client *client)
         if (rc)
                 goto exit;
 
+#ifdef CONFIG_RTC_DRV_M41T80_WDT
+        if (chip->features & M41T80_FEATURE_HT) {
+                rc = misc_register(&wdt_dev);
+                if (rc)
+                        goto exit;
+                rc = register_reboot_notifier(&wdt_notifier);
+                if (rc) {
+                        misc_deregister(&wdt_dev);
+                        goto exit;
+                }
+                save_client = client;
+        }
+#endif
         return 0;
 
 st_err:
@@ -595,6 +877,12 @@ static int m41t80_remove(struct i2c_client *client)
         struct m41t80_data *clientdata = i2c_get_clientdata(client);
         struct rtc_device *rtc = clientdata->rtc;
 
+#ifdef CONFIG_RTC_DRV_M41T80_WDT
+        if (clientdata->chip->features & M41T80_FEATURE_HT) {
+                misc_deregister(&wdt_dev);
+                unregister_reboot_notifier(&wdt_notifier);
+        }
+#endif
         if (rtc)
                 rtc_device_unregister(rtc);
         kfree(clientdata);