[WATCHDOG] Basic support for GE Fanuc's FPGA based watchdog timer

GE Fanuc SBC610

Support for the FPGA based watchdog timer as found on GE Fanuc's SBC310,
SBC610 and PPC9A Single Board Computers.

This patch adds support for the watchdog timer found in one of the devices
FPGAs. There are two identical watchdog timers at different offsets in the
above mentioned boards, this driver is capable of supporting one of them.
The watchdog timers are also capable of generating interrupts at a
user-configurable threshold, though support for this operation is currently
not supported by the driver.

Signed-off-by: Martyn Welch <martyn.welch@gefanuc.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/Kconfig

@@ -770,6 +770,12 @@ config TXX9_WDT
 
 # POWERPC Architecture
 
+config GEF_WDT
+	tristate "GE Fanuc Watchdog Timer"
+	depends on GEF_SBC610
+	---help---
+	  Watchdog timer found in a number of GE Fanuc single board computers.
+
 config MPC5200_WDT
 	tristate "MPC5200 Watchdog Timer"
 	depends on PPC_MPC52xx

drivers/watchdog/Makefile

@@ -111,6 +111,7 @@ obj-$(CONFIG_TXX9_WDT) += txx9wdt.o
 # PARISC Architecture
 
 # POWERPC Architecture
+obj-$(CONFIG_GEF_WDT) += gef_wdt.o
 obj-$(CONFIG_MPC5200_WDT) += mpc5200_wdt.o
 obj-$(CONFIG_8xxx_WDT) += mpc8xxx_wdt.o
 obj-$(CONFIG_MV64X60_WDT) += mv64x60_wdt.o

drivers/watchdog/gef_wdt.c

@@ -0,0 +1,330 @@
+/*
+ * GE Fanuc watchdog userspace interface
+ *
+ * Author:  Martyn Welch <martyn.welch@gefanuc.com>
+ *
+ * Copyright 2008 GE Fanuc Intelligent Platforms Embedded Systems, Inc.
+ *
+ * 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.
+ *
+ * Based on: mv64x60_wdt.c (MV64X60 watchdog userspace interface)
+ *   Author: James Chapman <jchapman@katalix.com>
+ */
+
+/* TODO:
+ * This driver does not provide support for the hardwares capability of sending
+ * an interrupt at a programmable threshold.
+ *
+ * This driver currently can only support 1 watchdog - there are 2 in the
+ * hardware that this driver supports. Thus one could be configured as a
+ * process-based watchdog (via /dev/watchdog), the second (using the interrupt
+ * capabilities) a kernel-based watchdog.
+ */
+
+#include <linux/kernel.h>
+#include <linux/compiler.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/miscdevice.h>
+#include <linux/watchdog.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/io.h>
+#include <linux/uaccess.h>
+
+#include <sysdev/fsl_soc.h>
+
+/*
+ * The watchdog configuration register contains a pair of 2-bit fields,
+ *   1.  a reload field, bits 27-26, which triggers a reload of
+ *       the countdown register, and
+ *   2.  an enable field, bits 25-24, which toggles between
+ *       enabling and disabling the watchdog timer.
+ * Bit 31 is a read-only field which indicates whether the
+ * watchdog timer is currently enabled.
+ *
+ * The low 24 bits contain the timer reload value.
+ */
+#define GEF_WDC_ENABLE_SHIFT	24
+#define GEF_WDC_SERVICE_SHIFT	26
+#define GEF_WDC_ENABLED_SHIFT	31
+
+#define GEF_WDC_ENABLED_TRUE	1
+#define GEF_WDC_ENABLED_FALSE	0
+
+/* Flags bits */
+#define GEF_WDOG_FLAG_OPENED	0
+
+static unsigned long wdt_flags;
+static int wdt_status;
+static void __iomem *gef_wdt_regs;
+static int gef_wdt_timeout;
+static int gef_wdt_count;
+static unsigned int bus_clk;
+static char expect_close;
+static DEFINE_SPINLOCK(gef_wdt_spinlock);
+
+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 int gef_wdt_toggle_wdc(int enabled_predicate, int field_shift)
+{
+	u32 data;
+	u32 enabled;
+	int ret = 0;
+
+	spin_lock(&gef_wdt_spinlock);
+	data = ioread32be(gef_wdt_regs);
+	enabled = (data >> GEF_WDC_ENABLED_SHIFT) & 1;
+
+	/* only toggle the requested field if enabled state matches predicate */
+	if ((enabled ^ enabled_predicate) == 0) {
+		/* We write a 1, then a 2 -- to the appropriate field */
+		data = (1 << field_shift) | gef_wdt_count;
+		iowrite32be(data, gef_wdt_regs);
+
+		data = (2 << field_shift) | gef_wdt_count;
+		iowrite32be(data, gef_wdt_regs);
+		ret = 1;
+	}
+	spin_unlock(&gef_wdt_spinlock);
+
+	return ret;
+}
+
+static void gef_wdt_service(void)
+{
+	gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
+		GEF_WDC_SERVICE_SHIFT);
+}
+
+static void gef_wdt_handler_enable(void)
+{
+	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_FALSE,
+				   GEF_WDC_ENABLE_SHIFT)) {
+		gef_wdt_service();
+		printk(KERN_NOTICE "gef_wdt: watchdog activated\n");
+	}
+}
+
+static void gef_wdt_handler_disable(void)
+{
+	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
+				   GEF_WDC_ENABLE_SHIFT))
+		printk(KERN_NOTICE "gef_wdt: watchdog deactivated\n");
+}
+
+static void gef_wdt_set_timeout(unsigned int timeout)
+{
+	/* maximum bus cycle count is 0xFFFFFFFF */
+	if (timeout > 0xFFFFFFFF / bus_clk)
+		timeout = 0xFFFFFFFF / bus_clk;
+
+	/* Register only holds upper 24 bits, bit shifted into lower 24 */
+	gef_wdt_count = (timeout * bus_clk) >> 8;
+	gef_wdt_timeout = timeout;
+}
+
+
+static ssize_t gef_wdt_write(struct file *file, const char __user *data,
+				 size_t len, loff_t *ppos)
+{
+	if (len) {
+		if (!nowayout) {
+			size_t i;
+
+			expect_close = 0;
+
+			for (i = 0; i != len; i++) {
+				char c;
+				if (get_user(c, data + i))
+					return -EFAULT;
+				if (c == 'V')
+					expect_close = 42;
+			}
+		}
+		gef_wdt_service();
+	}
+
+	return len;
+}
+
+static long gef_wdt_ioctl(struct file *file, unsigned int cmd,
+							unsigned long arg)
+{
+	int timeout;
+	int options;
+	void __user *argp = (void __user *)arg;
+	static struct watchdog_info info = {
+		.options =	WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
+				WDIOF_KEEPALIVEPING,
+		.firmware_version = 0,
+		.identity = "GE Fanuc watchdog",
+	};
+
+	switch (cmd) {
+	case WDIOC_GETSUPPORT:
+		if (copy_to_user(argp, &info, sizeof(info)))
+			return -EFAULT;
+		break;
+
+	case WDIOC_GETSTATUS:
+	case WDIOC_GETBOOTSTATUS:
+		if (put_user(wdt_status, (int __user *)argp))
+			return -EFAULT;
+		wdt_status &= ~WDIOF_KEEPALIVEPING;
+		break;
+
+	case WDIOC_SETOPTIONS:
+		if (get_user(options, (int __user *)argp))
+			return -EFAULT;
+
+		if (options & WDIOS_DISABLECARD)
+			gef_wdt_handler_disable();
+
+		if (options & WDIOS_ENABLECARD)
+			gef_wdt_handler_enable();
+		break;
+
+	case WDIOC_KEEPALIVE:
+		gef_wdt_service();
+		wdt_status |= WDIOF_KEEPALIVEPING;
+		break;
+
+	case WDIOC_SETTIMEOUT:
+		if (get_user(timeout, (int __user *)argp))
+			return -EFAULT;
+		gef_wdt_set_timeout(timeout);
+		/* Fall through */
+
+	case WDIOC_GETTIMEOUT:
+		if (put_user(gef_wdt_timeout, (int __user *)argp))
+			return -EFAULT;
+		break;
+
+	default:
+		return -ENOTTY;
+	}
+
+	return 0;
+}
+
+static int gef_wdt_open(struct inode *inode, struct file *file)
+{
+	if (test_and_set_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags))
+		return -EBUSY;
+
+	if (nowayout)
+		__module_get(THIS_MODULE);
+
+	gef_wdt_handler_enable();
+
+	return nonseekable_open(inode, file);
+}
+
+static int gef_wdt_release(struct inode *inode, struct file *file)
+{
+	if (expect_close == 42)
+		gef_wdt_handler_disable();
+	else {
+		printk(KERN_CRIT
+		       "gef_wdt: unexpected close, not stopping timer!\n");
+		gef_wdt_service();
+	}
+	expect_close = 0;
+
+	clear_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags);
+
+	return 0;
+}
+
+static const struct file_operations gef_wdt_fops = {
+	.owner = THIS_MODULE,
+	.llseek = no_llseek,
+	.write = gef_wdt_write,
+	.unlocked_ioctl = gef_wdt_ioctl,
+	.open = gef_wdt_open,
+	.release = gef_wdt_release,
+};
+
+static struct miscdevice gef_wdt_miscdev = {
+	.minor = WATCHDOG_MINOR,
+	.name = "watchdog",
+	.fops = &gef_wdt_fops,
+};
+
+
+static int __devinit gef_wdt_probe(struct of_device *dev,
+	const struct of_device_id *match)
+{
+	int timeout = 10;
+	u32 freq;
+
+	bus_clk = 133; /* in MHz */
+
+	freq = fsl_get_sys_freq();
+	if (freq > 0)
+		bus_clk = freq;
+
+	/* Map devices registers into memory */
+	gef_wdt_regs = of_iomap(dev->node, 0);
+	if (gef_wdt_regs == NULL)
+		return -ENOMEM;
+
+	gef_wdt_set_timeout(timeout);
+
+	gef_wdt_handler_disable();	/* in case timer was already running */
+
+	return misc_register(&gef_wdt_miscdev);
+}
+
+static int __devexit gef_wdt_remove(struct platform_device *dev)
+{
+	misc_deregister(&gef_wdt_miscdev);
+
+	gef_wdt_handler_disable();
+
+	iounmap(gef_wdt_regs);
+
+	return 0;
+}
+
+static const struct of_device_id gef_wdt_ids[] = {
+	{
+		.compatible = "gef,fpga-wdt",
+	},
+	{},
+};
+
+static struct of_platform_driver gef_wdt_driver = {
+	.owner		= THIS_MODULE,
+	.name		= "gef_wdt",
+	.match_table	= gef_wdt_ids,
+	.probe		= gef_wdt_probe,
+};
+
+static int __init gef_wdt_init(void)
+{
+	printk(KERN_INFO "GE Fanuc watchdog driver\n");
+	return of_register_platform_driver(&gef_wdt_driver);
+}
+
+static void __exit gef_wdt_exit(void)
+{
+	of_unregister_platform_driver(&gef_wdt_driver);
+}
+
+module_init(gef_wdt_init);
+module_exit(gef_wdt_exit);
+
+MODULE_AUTHOR("Martyn Welch <martyn.welch@gefanuc.com>");
+MODULE_DESCRIPTION("GE Fanuc watchdog driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
+MODULE_ALIAS("platform: gef_wdt");