[WATCHDOG] mpc83xx_wdt: add support for MPC86xx CPUs

On MPC86xx the watchdog could be enabled only at power-on-reset, and could
not be disabled afterwards.  We must ping the watchdog from the kernel
until the userspace handles it.

MPC83xx CPUs are only differ in a way that watchdog could be disabled
once, but after it was enabled via software it becomes just the same as
MPC86xx.

Thus, to support MPC86xx I added the kernel timer which pings the watchdog
until the userspace opens it.

Since we implemented the timer, now we're able to implement proper
handling for the CONFIG_WATCHDOG_NOWAYOUT case, for MPC83xx and MPC86xx.

Also move the probe code into subsys_initcall, because we want start
pinging the watchdog ASAP, and misc devices are available in
subsys_initcall.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 74 insertions, 10 deletions

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 48399e134c0d..93329620f447 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -696,8 +696,8 @@ config 8xx_WDT
         depends on 8xx
 
 config 83xx_WDT
-        tristate "MPC83xx Watchdog Timer"
-        depends on PPC_83xx
+        tristate "MPC83xx/MPC86xx Watchdog Timer"
+        depends on PPC_83xx || PPC_86xx
 
 config MV64X60_WDT
         tristate "MV64X60 (Marvell Discovery) Watchdog Timer"
diff --git a/drivers/watchdog/mpc83xx_wdt.c b/drivers/watchdog/mpc83xx_wdt.c
index 5f1b7bff8f12..fa82ec99ba81 100644
--- a/drivers/watchdog/mpc83xx_wdt.c
+++ b/drivers/watchdog/mpc83xx_wdt.c
@@ -1,10 +1,12 @@
 /*
- * mpc83xx_wdt.c - MPC83xx watchdog userspace interface
+ * mpc83xx_wdt.c - MPC83xx/MPC86xx watchdog userspace interface
  *
  * Authors: Dave Updegraff <dave@cray.org>
  *          Kumar Gala <galak@kernel.crashing.org>
  *              Attribution: from 83xx_wst: Florian Schirmer <jolt@tuxbox.org>
  *                              ..and from sc520_wdt
+ * Copyright (c) 2008  MontaVista Software, Inc.
+ *                     Anton Vorontsov <avorontsov@ru.mvista.com>
  *
  * Note: it appears that you can only actually ENABLE or DISABLE the thing
  * once after POR. Once enabled, you cannot disable, and vice versa.
@@ -18,6 +20,7 @@
 #include <linux/fs.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
+#include <linux/timer.h>
 #include <linux/miscdevice.h>
 #include <linux/of_platform.h>
 #include <linux/module.h>
@@ -39,6 +42,11 @@ struct mpc83xx_wdt {
         u8 res2[0xF0];
 };
 
+struct mpc83xx_wdt_type {
+        int prescaler;
+        bool hw_enabled;
+};
+
 static struct mpc83xx_wdt __iomem *wd_base;
 
 static u16 timeout = 0xffff;
@@ -51,6 +59,11 @@ module_param(reset, bool, 0);
 MODULE_PARM_DESC(reset,
         "Watchdog Interrupt/Reset Mode. 0 = interrupt, 1 = reset");
 
+static int nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, int, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
+                 "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
 /*
  * We always prescale, but if someone really doesn't want to they can set this
  * to 0
@@ -70,6 +83,22 @@ static void mpc83xx_wdt_keepalive(void)
         spin_unlock(&wdt_spinlock);
 }
 
+static void mpc83xx_wdt_timer_ping(unsigned long arg);
+static DEFINE_TIMER(wdt_timer, mpc83xx_wdt_timer_ping, 0, 0);
+
+static void mpc83xx_wdt_timer_ping(unsigned long arg)
+{
+        mpc83xx_wdt_keepalive();
+        /* We're pinging it twice faster than needed, just to be sure. */
+        mod_timer(&wdt_timer, jiffies + HZ * timeout_sec / 2);
+}
+
+static void mpc83xx_wdt_pr_warn(const char *msg)
+{
+        pr_crit("mpc83xx_wdt: %s, expect the %s soon!\n", msg,
+                reset ? "reset" : "machine check exception");
+}
+
 static ssize_t mpc83xx_wdt_write(struct file *file, const char __user *buf,
                                  size_t count, loff_t *ppos)
 {
@@ -85,7 +114,8 @@ static int mpc83xx_wdt_open(struct inode *inode, struct file *file)
                 return -EBUSY;
 
         /* Once we start the watchdog we can't stop it */
-        __module_get(THIS_MODULE);
+        if (nowayout)
+                __module_get(THIS_MODULE);
 
         /* Good, fire up the show */
         if (prescale)
@@ -97,13 +127,17 @@ static int mpc83xx_wdt_open(struct inode *inode, struct file *file)
 
         out_be32(&wd_base->swcrr, tmp);
 
+        del_timer_sync(&wdt_timer);
+
         return nonseekable_open(inode, file);
 }
 
 static int mpc83xx_wdt_release(struct inode *inode, struct file *file)
 {
-        printk(KERN_CRIT "Unexpected close, not stopping watchdog!\n");
-        mpc83xx_wdt_keepalive();
+        if (!nowayout)
+                mpc83xx_wdt_timer_ping(0);
+        else
+                mpc83xx_wdt_pr_warn("watchdog closed");
         clear_bit(0, &wdt_is_open);
         return 0;
 }
@@ -154,15 +188,25 @@ static int __devinit mpc83xx_wdt_probe(struct of_device *ofdev,
                                        const struct of_device_id *match)
 {
         int ret;
+        struct device_node *np = ofdev->node;
+        struct mpc83xx_wdt_type *wdt_type = match->data;
         u32 freq = fsl_get_sys_freq();
+        bool enabled;
 
         if (!freq || freq == -1)
                 return -EINVAL;
 
-        wd_base = of_iomap(ofdev->node, 0);
+        wd_base = of_iomap(np, 0);
         if (!wd_base)
                 return -ENOMEM;
 
+        enabled = in_be32(&wd_base->swcrr) & SWCRR_SWEN;
+        if (!enabled && wdt_type->hw_enabled) {
+                pr_info("mpc83xx_wdt: could not be enabled in software\n");
+                ret = -ENOSYS;
+                goto err_unmap;
+        }
+
         ret = misc_register(&mpc83xx_wdt_miscdev);
         if (ret) {
                 pr_err("cannot register miscdev on minor=%d (err=%d)\n",
@@ -172,13 +216,21 @@ static int __devinit mpc83xx_wdt_probe(struct of_device *ofdev,
 
         /* Calculate the timeout in seconds */
         if (prescale)
-                timeout_sec = (timeout * 0x10000) / freq;
+                timeout_sec = (timeout * wdt_type->prescaler) / freq;
         else
                 timeout_sec = timeout / freq;
 
         pr_info("WDT driver for MPC83xx initialized. mode:%s timeout=%d "
                 "(%d seconds)\n", reset ? "reset" : "interrupt", timeout,
                 timeout_sec);
+
+        /*
+         * If the watchdog was previously enabled or we're running on
+         * MPC86xx, we should ping the wdt from the kernel until the
+         * userspace handles it.
+         */
+        if (enabled)
+                mpc83xx_wdt_timer_ping(0);
         return 0;
 err_unmap:
         iounmap(wd_base);
@@ -187,6 +239,8 @@ err_unmap:
 
 static int __devexit mpc83xx_wdt_remove(struct of_device *ofdev)
 {
+        mpc83xx_wdt_pr_warn("watchdog removed");
+        del_timer_sync(&wdt_timer);
         misc_deregister(&mpc83xx_wdt_miscdev);
         iounmap(wd_base);
 
@@ -196,6 +250,16 @@ static int __devexit mpc83xx_wdt_remove(struct of_device *ofdev)
 static const struct of_device_id mpc83xx_wdt_match[] = {
         {
                 .compatible = "mpc83xx_wdt",
+                .data = &(struct mpc83xx_wdt_type) {
+                        .prescaler = 0x10000,
+                },
+        },
+        {
+                .compatible = "fsl,mpc8610-wdt",
+                .data = &(struct mpc83xx_wdt_type) {
+                        .prescaler = 0x10000,
+                        .hw_enabled = true,
+                },
         },
         {},
 };
@@ -221,10 +285,10 @@ static void __exit mpc83xx_wdt_exit(void)
         of_unregister_platform_driver(&mpc83xx_wdt_driver);
 }
 
-module_init(mpc83xx_wdt_init);
+subsys_initcall(mpc83xx_wdt_init);
 module_exit(mpc83xx_wdt_exit);
 
 MODULE_AUTHOR("Dave Updegraff, Kumar Gala");
-MODULE_DESCRIPTION("Driver for watchdog timer in MPC83xx uProcessor");
+MODULE_DESCRIPTION("Driver for watchdog timer in MPC83xx/MPC86xx uProcessors");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);