[PATCH] Add support for SB1 hardware watchdog, try#2

[Andrew Sharp <andy.sharp@onstor.com>]

This patch is for watchdog timers built into SiByte MIPS SoCs.

Resend with changes from comments.


Signed-off-by: Andy Sharp <andy.sharp@onstor.com>
---
 drivers/watchdog/Kconfig   |   13 ++
 drivers/watchdog/Makefile  |    1 +
 drivers/watchdog/sb_wdog.c |  362 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 376 insertions(+), 0 deletions(-)

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 2792bc1..9057362 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -616,6 +616,19 @@ config AR7_WDT
 	help
 	  Hardware driver for the TI AR7 Watchdog Timer.
 
+config SIBYTE_WDOG
+	tristate "Sibyte SoC hardware watchdog"
+	depends on CPU_SB1
+	help
+	  Watchdog driver for the built in watchdog hardware in Sibyte
+	  SoC processors.  There are apparently two watchdog timers
+	  on such processors; this driver supports only the first one,
+	  because currently Linux only supports exporting one watchdog
+	  to userspace.
+
+	  To compile this driver as a loadable module, choose M here.
+	  The module will be called sb_wdog.
+
 # PARISC Architecture
 
 # POWERPC Architecture
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 7d9e573..eb3822b 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -91,6 +91,7 @@ obj-$(CONFIG_INDYDOG) += indydog.o
 obj-$(CONFIG_WDT_MTX1)	+= mtx-1_wdt.o
 obj-$(CONFIG_WDT_RM9K_GPI) += rm9k_wdt.o
 obj-$(CONFIG_AR7_WDT) += ar7_wdt.o
+obj-$(CONFIG_SIBYTE_WDOG) += sb_wdog.o
 
 # PARISC Architecture
 
diff --git a/drivers/watchdog/sb_wdog.c b/drivers/watchdog/sb_wdog.c
new file mode 100644
index 0000000..d2a0886
--- /dev/null
+++ b/drivers/watchdog/sb_wdog.c
@@ -0,0 +1,362 @@
+/*
+ * Watchdog driver for SiByte SB1 SoCs
+ *
+ * Copyright (C) 2007 OnStor, Inc. * Andrew Sharp <andy.sharp@onstor.com>
+ *
+ * This driver is intended to make the second of two hardware watchdogs
+ * on the Sibyte 12XX and 11XX SoCs available to the user.  There are two
+ * such devices available on the SoC, but it seems that there isn't an
+ * enumeration class for watchdogs in Linux like there is for RTCs.
+ * The second is used rather than the first because it uses IRQ 1,
+ * thereby avoiding all that IRQ 0 problematic nonsense.
+ *
+ * I have not tried this driver on a 1480 processor; it might work
+ * just well enough to really screw things up.
+ *
+ * It is a simple timer, and there is an interrupt that is raised the
+ * first time the timer expires.  The second time it expires, the chip
+ * is reset and there is no way to redirect that NMI.  Which could
+ * be problematic in some cases where this chip is sitting on the HT
+ * bus and has just taken responsibility for providing a cache block.
+ * Since the reset can't be redirected to the external reset pin, it is
+ * possible that other HT connected processors might hang and not reset.
+ * For Linux, a soft reset would probably be even worse than a hard reset.
+ * There you have it.
+ *
+ * The timer takes 23 bits of a 64 bit register (?) as a count value,
+ * and decrements the count every microsecond, for a max value of
+ * 0x7fffff usec or about 8.3ish seconds.
+ *
+ * This watchdog borrows some user semantics from the softdog driver,
+ * in that if you close the fd, it leaves the watchdog running, unless
+ * you previously wrote a 'V' to the fd, in which case it disables
+ * the watchdog when you close the fd like some other drivers.
+ *
+ * Based on various other watchdog drivers, which are probably all
+ * loosely based on something Alan Cox wrote years ago.
+ *
+ *	(c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.
+ *				http://www.redhat.com
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	version 1 or 2 as published by the Free Software Foundation.
+ *
+ */
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/uaccess.h>
+#include <linux/fs.h>
+#include <linux/reboot.h>
+#include <linux/miscdevice.h>
+#include <linux/watchdog.h>
+#include <linux/interrupt.h>
+
+#include <asm/sibyte/sb1250.h>
+#include <asm/sibyte/sb1250_regs.h>
+#include <asm/sibyte/sb1250_int.h>
+#include <asm/sibyte/sb1250_scd.h>
+
+
+/*
+ * set the initial count value of a timer
+ *
+ * wdog is the iomem address of the cfg register
+ */
+ void
+sbwdog_set(char __iomem *wdog, unsigned long t)
+{
+	__raw_writeb(0, wdog - 0x10);
+	__raw_writeq(t & 0x7fffffUL, wdog);
+}
+
+/*
+ * cause the timer to [re]load it's initial count and start counting
+ * all over again
+ *
+ * wdog is the iomem address of the cfg register
+ */
+ void
+sbwdog_pet(char __iomem *wdog)
+{
+	__raw_writeb(__raw_readb(wdog) | 1, wdog);
+}
+
+static unsigned long sbwdog_gate; /* keeps it to one thread only */
+static char __iomem *kern_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_0));
+static char __iomem *user_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_1));
+static unsigned long timeout = 0x7fffffUL;	/* useconds: 8.3ish secs. */
+static int expect_close;
+
+static struct watchdog_info ident = {
+	.options	= WDIOF_CARDRESET | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
+	.identity	= "SiByte Watchdog",
+};
+
+/*
+ * Allow only a single thread to walk the dog
+ */
+ static int
+sbwdog_open(struct inode *inode, struct file *file)
+{
+	nonseekable_open(inode, file);
+	if (test_and_set_bit(0, &sbwdog_gate)) {
+		return -EBUSY;
+	}
+	__module_get(THIS_MODULE);
+
+	/*
+	 * Activate the timer
+	 */
+	sbwdog_set(user_dog, timeout);
+	__raw_writeb(1, user_dog);
+
+	return 0;
+}
+
+/*
+ * Put the dog back in the kennel.
+ */
+ static int
+sbwdog_release(struct inode *inode, struct file *file)
+{
+	if (expect_close == 42) {
+		__raw_writeb(0, user_dog);
+		module_put(THIS_MODULE);
+	} else {
+		printk(KERN_CRIT "%s: Unexpected close, not stopping watchdog!\n",
+			ident.identity);
+		sbwdog_pet(user_dog);
+	}
+	clear_bit(0, &sbwdog_gate);
+	expect_close = 0;
+
+	return 0;
+}
+
+/*
+ * 42 - the answer
+ */
+ static ssize_t
+sbwdog_write(struct file *file, const char __user *data, size_t len,
+	loff_t *ppos)
+{
+	int i;
+
+	if (len) {
+		/*
+		 * restart the timer
+		 */
+		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;
+			}
+		}
+		sbwdog_pet(user_dog);
+	}
+
+	return len;
+}
+
+ static int
+sbwdog_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
+	unsigned long arg)
+{
+	int ret = -ENOTTY;
+	unsigned long time;
+	void __user *argp = (void __user *)arg;
+	int __user *p = argp;
+
+	switch (cmd) {
+	case WDIOC_GETSUPPORT:
+		ret = copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
+		break;
+
+	case WDIOC_GETSTATUS:
+	case WDIOC_GETBOOTSTATUS:
+		ret = put_user(0, p);
+		break;
+
+	case WDIOC_SETTIMEOUT:
+		ret = get_user(time, p);
+		if (ret) {
+			break;
+		}
+
+		time *= 1000000;
+		if (time > 0x7fffffUL) {
+			ret = -EINVAL;
+			break;
+		}
+		timeout = time;
+		sbwdog_set(user_dog, timeout);
+		sbwdog_pet(user_dog);
+
+	case WDIOC_GETTIMEOUT:
+		/*
+		 * get the remaining count from the ... count register
+		 * which is 1*8 before the config register
+		 */
+		ret = put_user(__raw_readq(user_dog - 8) / 1000000, p);
+		break;
+
+	case WDIOC_KEEPALIVE:
+		sbwdog_pet(user_dog);
+		ret = 0;
+		break;
+	}
+	return ret;
+}
+
+/*
+ *	Notifier for system down
+ */
+ static int
+sbwdog_notify_sys(struct notifier_block *this, unsigned long code, void *erf)
+{
+	if (code == SYS_DOWN || code == SYS_HALT) {
+		/*
+		 * sit and sit
+		 */
+		__raw_writeb(0, user_dog);
+		__raw_writeb(0, kern_dog);
+	}
+
+	return NOTIFY_DONE;
+}
+
+static const struct file_operations sbwdog_fops =
+{
+	.owner		= THIS_MODULE,
+	.llseek		= no_llseek,
+	.write		= sbwdog_write,
+	.ioctl		= sbwdog_ioctl,
+	.open		= sbwdog_open,
+	.release	= sbwdog_release,
+};
+
+static struct miscdevice sbwdog_miscdev =
+{
+	.minor		= WATCHDOG_MINOR,
+	.name		= "watchdog",
+	.fops		= &sbwdog_fops,
+};
+
+static struct notifier_block sbwdog_notifier = {
+	.notifier_call	= sbwdog_notify_sys,
+};
+
+/*
+ * interrupt handler
+ *
+ * doesn't do a whole lot for user, but oh so cleverly written so kernel
+ * code can use it to re-up the watchdog, thereby saving the kernel from
+ * having to create and maintain a timer, just to tickle another timer,
+ * which is just so wrong.
+ */
+ irqreturn_t
+sbwdog_interrupt(int irq, void *addr)
+{
+	unsigned long wd_init;
+	char *wd_cfg_reg = (char *)addr;
+	u8 cfg;
+
+	cfg = __raw_readb(wd_cfg_reg);
+	wd_init = __raw_readq(wd_cfg_reg - 8) & 0x7fffff;
+
+	/*
+	 * if it's the second watchdog timer, it's for those users
+	 */
+	if (wd_cfg_reg == user_dog) {
+		printk(KERN_CRIT
+			"%s in danger of initiating system reset in %ld.%01ld seconds\n",
+			ident.identity, wd_init / 1000000, (wd_init / 100000) % 10);
+	} else {
+		cfg |= 1;
+	}
+
+	__raw_writeb(cfg, wd_cfg_reg);
+
+	return IRQ_HANDLED;
+}
+
+ static int __init
+sbwdog_init(void)
+{
+	int ret;
+
+	/*
+	 * register a reboot notifier
+	 */
+	ret = register_reboot_notifier(&sbwdog_notifier);
+	if (ret) {
+		printk (KERN_ERR "%s: cannot register reboot notifier (err=%d)\n",
+			ident.identity, ret);
+		return ret;
+	}
+
+	/*
+	 * get the resources
+	 */
+	ret = misc_register(&sbwdog_miscdev);
+	if (ret == 0) {
+		printk(KERN_INFO "%s: timeout is %ld.%ld secs\n", ident.identity,
+			timeout / 1000000, (timeout / 100000) % 10);
+	}
+
+	ret = request_irq(1, sbwdog_interrupt, IRQF_DISABLED | IRQF_SHARED,
+		ident.identity, (void *)user_dog);
+	if (ret) {
+		printk(KERN_ERR "%s: failed to request irq 1 - %d\n", ident.identity,
+			ret);
+		misc_deregister(&sbwdog_miscdev);
+	}
+
+	return ret;
+}
+
+ static void __exit
+sbwdog_exit(void)
+{
+	misc_deregister(&sbwdog_miscdev);
+}
+
+module_init(sbwdog_init);
+module_exit(sbwdog_exit);
+
+MODULE_AUTHOR("Andrew Sharp <andy.sharp@onstor.com>");
+MODULE_DESCRIPTION("SiByte Watchdog");
+
+module_param(timeout, ulong, 0);
+MODULE_PARM_DESC(timeout,
+	"Watchdog timeout in microseconds (max/default 8388607 or 8.3ish secs)");
+
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
+
+/*
+ * example code that can be put in a platform code area to utilize the
+ * first watchdog timer for the kernels own purpose.
+
+ void
+platform_wd_setup(void)
+{
+	int ret;
+
+	ret = request_irq(0, sbwdog_interrupt, IRQF_DISABLED | IRQF_SHARED,
+		"Kernel Watchdog", IOADDR(A_SCD_WDOG_CFG_0));
+	if (ret) {
+		printk(KERN_CRIT "Watchdog IRQ zero(0) failed to be requested - %d\n",
+			ret);
+	}
+}
+
+
+ */