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Date:	Tue,  8 Feb 2011 14:22:02 +0100
From:	Tobias Klauser <tklauser@...tanz.ch>
To:	Wim Van Sebroeck <wim@...ana.be>, linux-watchdog@...r.kernel.org
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	nios2-dev@...c.et.ntust.edu.tw
Subject: [PATCH v2] watchdog: Add driver for Altera Watchdog Timer

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@...tanz.ch>
---

Thanks a lot to Jamie Iles for reviewing the first submitted version of this
driver.

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                      |  310 ++++++++++++++++++++
 4 files changed, 326 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..dbced1e
--- /dev/null
+++ b/drivers/watchdog/altera_wdt.c
@@ -0,0 +1,310 @@
+/*
+ * Driver for the Altera Watchdog Timer
+ *
+ * Copyright (C) 2011 Tobias Klauser <tklauser@...tanz.ch>
+ * Copyright (C) 2005 Walter Goossens
+ *
+ * Originally based on wdt.c which is
+ *
+ * Copyright (C) 1995-1997 Alan Cox <alan@...rguk.ukuu.org.uk>
+ *
+ * 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 int 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);
+	return 0;
+}
+
+/*
+ * 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 u32 *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@...tanz.ch>");
+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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