[PATCH v3] watchdog: Add driver for Altera Watchdog Timer

[Tobias Klauser]

This driver adds support for the Altera Timer in the Watchdog Timer
configuration. This component is usually found on SOPC (System on
Programmable Chip) for Altera FPGAs.

Signed-off-by: Tobias Klauser <tklauser@xxxxxxxxxx>
Reviewed-by: Jamie Iles <jamie@xxxxxxxxxxxxx>
---
Thanks a lot to Jamie Iles and Walter Goossens for their feedback on v2.

changes for v3:
 - Make altera_wdt_setup static void (as suggested by Jamie)
 - Use const __be32 * for devicetree properties (as suggested by Walter)
changes for v2:
 - Get driver properties from devicetree (and document them), thus the
   driver depends on OF
 - Do not select WATCHDOG_NOWAYOUT, but instead implement a software
   timer resetting the watchdog timer when the device is not open
 - Only support a single instance of the watchdog, so the private data
   can be kept in static data
 - Use devm_* functions in altera_wdt_probe to simplify cleanup and
   error handling
 - Remove empty altera_wdt_shutdown function
 - Add MODULE_LICENSE (GPL)


 .../devicetree/bindings/watchdog/altera_wdt.txt    |    7 +
 drivers/watchdog/Kconfig                           |    8 +
 drivers/watchdog/Makefile                          |    1 +
 drivers/watchdog/altera_wdt.c                      |  309 ++++++++++++++++++++
 4 files changed, 325 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/watchdog/altera_wdt.txt
 create mode 100644 drivers/watchdog/altera_wdt.c

diff --git a/Documentation/devicetree/bindings/watchdog/altera_wdt.txt b/Documentation/devicetree/bindings/watchdog/altera_wdt.txt
new file mode 100644
index 0000000..16ac949
--- /dev/null
+++ b/Documentation/devicetree/bindings/watchdog/altera_wdt.txt
@@ -0,0 +1,7 @@
+Altera Watchdog Timer
+
+Required properties:
+- compatible : should be "ALTR,wdt-1.0"
+- clock-frequency : frequency of the clock input
+- timeout : load value of the timer (number of clock ticks until watchdog
+            resets)
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index bd6a33d..ebcafb0 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -69,6 +69,14 @@ config WM8350_WATCHDOG
 	  Support for the watchdog in the WM8350 AudioPlus PMIC.  When
 	  the watchdog triggers the system will be reset.
 
+config ALTERA_WDT
+	tristate "Altera Watchdog Timer"
+	depends on OF
+	help
+	  Support for the Altera Timer in the Watchdog Timer configuration. This
+	  component is found on SOPC (System on Programmable Chip) for Altera
+	  FPGAs.
+
 # ALPHA Architecture
 
 # ARM Architecture
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index fd9c8c0..48a2167 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -153,4 +153,5 @@ obj-$(CONFIG_WATCHDOG_CP1XXX)		+= cpwd.o
 obj-$(CONFIG_WM831X_WATCHDOG) += wm831x_wdt.o
 obj-$(CONFIG_WM8350_WATCHDOG) += wm8350_wdt.o
 obj-$(CONFIG_MAX63XX_WATCHDOG) += max63xx_wdt.o
+obj-$(CONFIG_ALTERA_WDT) += altera_wdt.o
 obj-$(CONFIG_SOFT_WATCHDOG) += softdog.o
diff --git a/drivers/watchdog/altera_wdt.c b/drivers/watchdog/altera_wdt.c
new file mode 100644
index 0000000..2a7f14a
--- /dev/null
+++ b/drivers/watchdog/altera_wdt.c
@@ -0,0 +1,309 @@
+/*
+ * Driver for the Altera Watchdog Timer
+ *
+ * Copyright (C) 2011 Tobias Klauser <tklauser@xxxxxxxxxx>
+ * Copyright (C) 2005 Walter Goossens
+ *
+ * Originally based on wdt.c which is
+ *
+ * Copyright (C) 1995-1997 Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
+ *
+ * Software timeout heartbeat code based on pika_wdt.c which is
+ *
+ * Copyright (c) 2008 PIKA Technologies
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/watchdog.h>
+#include <linux/platform_device.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/timer.h>
+#include <linux/io.h>
+#include <linux/uaccess.h>
+#include <linux/of_platform.h>
+
+#define WATCHDOG_NAME	"altera_wdt"
+
+/* Register offsets */
+#define ALTERA_WDT_STATUS	0x00
+#define ALTERA_WDT_CONTROL	0x04
+#define ALTERA_WDT_PERIODL	0x08
+#define ALTERA_WDT_PERIODH	0x0C
+
+#define ALTERA_WDT_RUN_BIT	0x04
+
+/* User land timeout */
+#define WDT_HEARTBEAT 15
+static int heartbeat = WDT_HEARTBEAT;
+module_param(heartbeat, int, 0);
+MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
+	"(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
+
+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) ")");
+
+static struct {
+	void __iomem *base;
+	unsigned long wdt_timeout;	/* timeout of the hardware timer */
+
+	unsigned long next_heartbeat;	/* the next_heartbeat for the timer */
+	unsigned long is_open;
+	char expect_close;
+	struct timer_list timer;	/* software timer that pings the watchdog */
+} altera_wdt_priv;
+
+/*
+ * Start the watchdog. Once it has been started, it cannot be stopped anymore.
+ */
+static void altera_wdt_setup(void)
+{
+	u32 control = readl(altera_wdt_priv.base + ALTERA_WDT_CONTROL);
+
+	writel(control | ALTERA_WDT_RUN_BIT, altera_wdt_priv.base + ALTERA_WDT_CONTROL);
+}
+
+/*
+ * Tickle the watchdog (reset the watchdog timer)
+ */
+static void altera_wdt_reset(void)
+{
+	/* It doesn't matter what value we write */
+	writel(1, altera_wdt_priv.base + ALTERA_WDT_PERIODL);
+}
+
+/*
+ * Software timer tick
+ */
+static void altera_wdt_ping(unsigned long data)
+{
+	if (time_before(jiffies, altera_wdt_priv.next_heartbeat) ||
+			(!nowayout && !altera_wdt_priv.is_open)) {
+		altera_wdt_reset();
+		mod_timer(&altera_wdt_priv.timer, jiffies + altera_wdt_priv.wdt_timeout);
+	} else
+		pr_crit(WATCHDOG_NAME ": I will reset your machine!\n");
+}
+
+static void altera_wdt_keepalive(void)
+{
+	altera_wdt_priv.next_heartbeat = jiffies + heartbeat * HZ;
+}
+
+static void altera_wdt_start(void)
+{
+	altera_wdt_keepalive();
+	mod_timer(&altera_wdt_priv.timer, jiffies + altera_wdt_priv.wdt_timeout);
+}
+
+static int altera_wdt_open(struct inode *inode, struct file *file)
+{
+	/* /dev/watchdog can only be opened once */
+	if (test_and_set_bit(0, &altera_wdt_priv.is_open))
+		return -EBUSY;
+
+	altera_wdt_start();
+
+	return nonseekable_open(inode, file);
+}
+
+static int altera_wdt_release(struct inode *inode, struct file *file)
+{
+	/* stop internal ping */
+	if (!altera_wdt_priv.expect_close)
+		del_timer(&altera_wdt_priv.timer);
+
+	clear_bit(0, &altera_wdt_priv.is_open);
+	altera_wdt_priv.expect_close = 0;
+
+	return 0;
+}
+
+static ssize_t altera_wdt_write(struct file *file, const char __user *data,
+		size_t len, loff_t *ppos)
+{
+	if (!len)
+		return 0;
+
+	/* Scan for magic character */
+	if (!nowayout) {
+		size_t i;
+
+		altera_wdt_priv.expect_close = 0;
+
+		for (i = 0; i < len; i++) {
+			char c;
+			if (get_user(c, data + i))
+				return -EFAULT;
+			if (c == 'V') {
+				altera_wdt_priv.expect_close = 42;
+				break;
+			}
+		}
+	}
+
+	altera_wdt_keepalive();
+
+	return len;
+}
+
+static const struct watchdog_info altera_wdt_info = {
+	.identity		= "Altera Watchdog",
+	.options		= WDIOF_SETTIMEOUT |
+				  WDIOF_KEEPALIVEPING |
+				  WDIOF_MAGICCLOSE,
+	.firmware_version	= 1,
+};
+
+static long altera_wdt_ioctl(struct file *file, unsigned int cmd,
+		unsigned long arg)
+{
+	void __user *argp = (void __user *) arg;
+	int __user *p = argp;
+	int new_value;
+
+	switch (cmd) {
+	case WDIOC_GETSUPPORT:
+		return copy_to_user(argp, &altera_wdt_info, sizeof(altera_wdt_info));
+
+	case WDIOC_GETSTATUS:
+	case WDIOC_GETBOOTSTATUS:
+		return put_user(0, p);
+
+	case WDIOC_KEEPALIVE:
+		altera_wdt_keepalive();
+		return 0;
+
+	case WDIOC_SETTIMEOUT:
+		if (get_user(new_value, p))
+			return -EFAULT;
+
+		heartbeat = new_value;
+		altera_wdt_keepalive();
+
+		return put_user(new_value, p);  /* return current value */
+
+	case WDIOC_GETTIMEOUT:
+		return put_user(heartbeat, p);
+
+	default:
+		return -ENOTTY;
+	}
+}
+
+static const struct file_operations altera_wdt_fops = {
+	.owner		= THIS_MODULE,
+	.llseek		= no_llseek,
+	.open		= altera_wdt_open,
+	.release	= altera_wdt_release,
+	.write		= altera_wdt_write,
+	.unlocked_ioctl	= altera_wdt_ioctl,
+};
+
+static struct miscdevice altera_wdt_miscdev = {
+	.minor	= WATCHDOG_MINOR,
+	.name	= "watchdog",
+	.fops	= &altera_wdt_fops,
+};
+
+static int __devinit altera_wdt_probe(struct platform_device *pdev)
+{
+	struct resource *res, *mem;
+	const __be32 *freq_prop, *timeout_prop;
+	unsigned long timeout;
+	int ret;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENOENT;
+
+	mem = devm_request_mem_region(&pdev->dev, res->start,
+				      resource_size(res), pdev->name);
+	if (!mem)
+		return -EBUSY;
+
+	altera_wdt_priv.base = devm_ioremap_nocache(&pdev->dev, mem->start,
+						    resource_size(mem));
+	if (!altera_wdt_priv.base)
+		return -ENOMEM;
+
+	freq_prop = of_get_property(pdev->dev.of_node, "clock-frequency", NULL);
+	if (!freq_prop)
+		return -ENODEV;
+
+	timeout_prop = of_get_property(pdev->dev.of_node, "timeout", NULL);
+	if (!timeout_prop)
+		return -ENODEV;
+
+	/* Add 1 as the timeout property actually holds the load value */
+	timeout = be32_to_cpup(timeout_prop) + 1;
+	/* Convert timeout to msecs */
+	timeout = timeout / (be32_to_cpup(freq_prop) / MSEC_PER_SEC);
+	/* Tickle the watchdog twice per timeout period */
+	altera_wdt_priv.wdt_timeout = msecs_to_jiffies(timeout / 2);
+
+	ret = misc_register(&altera_wdt_miscdev);
+	if (ret)
+		return ret;
+
+	altera_wdt_setup();
+	altera_wdt_priv.next_heartbeat = jiffies + heartbeat * HZ;
+	setup_timer(&altera_wdt_priv.timer, altera_wdt_ping, 0);
+	mod_timer(&altera_wdt_priv.timer, jiffies + altera_wdt_priv.wdt_timeout);
+
+	pr_info(WATCHDOG_NAME " enabled (heartbeat=%d sec, nowayout=%d)\n",
+		heartbeat, nowayout);
+
+	return 0;
+}
+
+static int __devexit altera_wdt_remove(struct platform_device *pdev)
+{
+	misc_deregister(&altera_wdt_miscdev);
+	return 0;
+}
+
+static struct of_device_id altera_wdt_match[] = {
+	{ .compatible = "altr,wdt-1.0", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, altera_wdt_match);
+
+static struct platform_driver altera_wdt_driver = {
+	.probe		= altera_wdt_probe,
+	.remove		= __devexit_p(altera_wdt_remove),
+	.driver		= {
+		.owner		= THIS_MODULE,
+		.name		= WATCHDOG_NAME,
+		.of_match_table	= altera_wdt_match,
+	},
+};
+
+static int __init altera_wdt_init(void)
+{
+	return platform_driver_register(&altera_wdt_driver);
+}
+
+static void __exit altera_wdt_exit(void)
+{
+	platform_driver_unregister(&altera_wdt_driver);
+}
+
+module_init(altera_wdt_init);
+module_exit(altera_wdt_exit);
+
+MODULE_AUTHOR("Walter Goossens, Tobias Klauser <tklauser@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Driver for Altera Watchdog Timer");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
+MODULE_ALIAS("platform:" WATCHDOG_NAME);
-- 
1.7.0.4

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