kernel-ark/drivers/watchdog/dw_wdt.c
Doug Anderson 04b1a62e6b watchdog: dw_wdt: keepalive the watchdog at write time
If you've got code that does this in a tight loop
  1. Open watchdog
  2. Send 'expect close'
  3. Close watchdog
...you'll eventually trigger a watchdog reset.  You can reproduce this
by using daisydog (1) and running:
  while true; do daisydog -c > /dev/null; done

The problem is that each time you write to the watchdog for 'expect
close' it moves the timer .5 seconds out.  The timer thus never fires
and never pats the watchdog for you.

1: http://git.chromium.org/gitweb/?p=chromiumos/third_party/daisydog.git

Signed-off-by: Doug Anderson <dianders@chromium.org>
Tested-by: Jisheng Zhang <jszhang@marvell.com>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
2015-06-22 15:54:31 +02:00

403 lines
9.5 KiB
C

/*
* Copyright 2010-2011 Picochip Ltd., Jamie Iles
* http://www.picochip.com
*
* 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.
*
* This file implements a driver for the Synopsys DesignWare watchdog device
* in the many subsystems. The watchdog has 16 different timeout periods
* and these are a function of the input clock frequency.
*
* The DesignWare watchdog cannot be stopped once it has been started so we
* use a software timer to implement a ping that will keep the watchdog alive.
* If we receive an expected close for the watchdog then we keep the timer
* running, otherwise the timer is stopped and the watchdog will expire.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/fs.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/notifier.h>
#include <linux/of.h>
#include <linux/pm.h>
#include <linux/platform_device.h>
#include <linux/reboot.h>
#include <linux/timer.h>
#include <linux/uaccess.h>
#include <linux/watchdog.h>
#define WDOG_CONTROL_REG_OFFSET 0x00
#define WDOG_CONTROL_REG_WDT_EN_MASK 0x01
#define WDOG_TIMEOUT_RANGE_REG_OFFSET 0x04
#define WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT 4
#define WDOG_CURRENT_COUNT_REG_OFFSET 0x08
#define WDOG_COUNTER_RESTART_REG_OFFSET 0x0c
#define WDOG_COUNTER_RESTART_KICK_VALUE 0x76
/* The maximum TOP (timeout period) value that can be set in the watchdog. */
#define DW_WDT_MAX_TOP 15
#define DW_WDT_DEFAULT_SECONDS 30
static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
#define WDT_TIMEOUT (HZ / 2)
static struct {
void __iomem *regs;
struct clk *clk;
unsigned long in_use;
unsigned long next_heartbeat;
struct timer_list timer;
int expect_close;
struct notifier_block restart_handler;
} dw_wdt;
static inline int dw_wdt_is_enabled(void)
{
return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) &
WDOG_CONTROL_REG_WDT_EN_MASK;
}
static inline int dw_wdt_top_in_seconds(unsigned top)
{
/*
* There are 16 possible timeout values in 0..15 where the number of
* cycles is 2 ^ (16 + i) and the watchdog counts down.
*/
return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk);
}
static int dw_wdt_get_top(void)
{
int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF;
return dw_wdt_top_in_seconds(top);
}
static inline void dw_wdt_set_next_heartbeat(void)
{
dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ;
}
static void dw_wdt_keepalive(void)
{
writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
WDOG_COUNTER_RESTART_REG_OFFSET);
}
static int dw_wdt_set_top(unsigned top_s)
{
int i, top_val = DW_WDT_MAX_TOP;
/*
* Iterate over the timeout values until we find the closest match. We
* always look for >=.
*/
for (i = 0; i <= DW_WDT_MAX_TOP; ++i)
if (dw_wdt_top_in_seconds(i) >= top_s) {
top_val = i;
break;
}
/*
* Set the new value in the watchdog. Some versions of dw_wdt
* have have TOPINIT in the TIMEOUT_RANGE register (as per
* CP_WDT_DUAL_TOP in WDT_COMP_PARAMS_1). On those we
* effectively get a pat of the watchdog right here.
*/
writel(top_val | top_val << WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT,
dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
/*
* Add an explicit pat to handle versions of the watchdog that
* don't have TOPINIT. This won't hurt on versions that have
* it.
*/
dw_wdt_keepalive();
dw_wdt_set_next_heartbeat();
return dw_wdt_top_in_seconds(top_val);
}
static int dw_wdt_restart_handle(struct notifier_block *this,
unsigned long mode, void *cmd)
{
u32 val;
writel(0, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET);
val = readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
if (val & WDOG_CONTROL_REG_WDT_EN_MASK)
writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs +
WDOG_COUNTER_RESTART_REG_OFFSET);
else
writel(WDOG_CONTROL_REG_WDT_EN_MASK,
dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
/* wait for reset to assert... */
mdelay(500);
return NOTIFY_DONE;
}
static void dw_wdt_ping(unsigned long data)
{
if (time_before(jiffies, dw_wdt.next_heartbeat) ||
(!nowayout && !dw_wdt.in_use)) {
dw_wdt_keepalive();
mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
} else
pr_crit("keepalive missed, machine will reset\n");
}
static int dw_wdt_open(struct inode *inode, struct file *filp)
{
if (test_and_set_bit(0, &dw_wdt.in_use))
return -EBUSY;
/* Make sure we don't get unloaded. */
__module_get(THIS_MODULE);
if (!dw_wdt_is_enabled()) {
/*
* The watchdog is not currently enabled. Set the timeout to
* something reasonable and then start it.
*/
dw_wdt_set_top(DW_WDT_DEFAULT_SECONDS);
writel(WDOG_CONTROL_REG_WDT_EN_MASK,
dw_wdt.regs + WDOG_CONTROL_REG_OFFSET);
}
dw_wdt_set_next_heartbeat();
return nonseekable_open(inode, filp);
}
static ssize_t dw_wdt_write(struct file *filp, const char __user *buf,
size_t len, loff_t *offset)
{
if (!len)
return 0;
if (!nowayout) {
size_t i;
dw_wdt.expect_close = 0;
for (i = 0; i < len; ++i) {
char c;
if (get_user(c, buf + i))
return -EFAULT;
if (c == 'V') {
dw_wdt.expect_close = 1;
break;
}
}
}
dw_wdt_set_next_heartbeat();
dw_wdt_keepalive();
mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
return len;
}
static u32 dw_wdt_time_left(void)
{
return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) /
clk_get_rate(dw_wdt.clk);
}
static const struct watchdog_info dw_wdt_ident = {
.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
WDIOF_MAGICCLOSE,
.identity = "Synopsys DesignWare Watchdog",
};
static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
unsigned long val;
int timeout;
switch (cmd) {
case WDIOC_GETSUPPORT:
return copy_to_user((void __user *)arg, &dw_wdt_ident,
sizeof(dw_wdt_ident)) ? -EFAULT : 0;
case WDIOC_GETSTATUS:
case WDIOC_GETBOOTSTATUS:
return put_user(0, (int __user *)arg);
case WDIOC_KEEPALIVE:
dw_wdt_set_next_heartbeat();
return 0;
case WDIOC_SETTIMEOUT:
if (get_user(val, (int __user *)arg))
return -EFAULT;
timeout = dw_wdt_set_top(val);
return put_user(timeout , (int __user *)arg);
case WDIOC_GETTIMEOUT:
return put_user(dw_wdt_get_top(), (int __user *)arg);
case WDIOC_GETTIMELEFT:
/* Get the time left until expiry. */
if (get_user(val, (int __user *)arg))
return -EFAULT;
return put_user(dw_wdt_time_left(), (int __user *)arg);
default:
return -ENOTTY;
}
}
static int dw_wdt_release(struct inode *inode, struct file *filp)
{
clear_bit(0, &dw_wdt.in_use);
if (!dw_wdt.expect_close) {
del_timer(&dw_wdt.timer);
if (!nowayout)
pr_crit("unexpected close, system will reboot soon\n");
else
pr_crit("watchdog cannot be disabled, system will reboot soon\n");
}
dw_wdt.expect_close = 0;
return 0;
}
#ifdef CONFIG_PM_SLEEP
static int dw_wdt_suspend(struct device *dev)
{
clk_disable_unprepare(dw_wdt.clk);
return 0;
}
static int dw_wdt_resume(struct device *dev)
{
int err = clk_prepare_enable(dw_wdt.clk);
if (err)
return err;
dw_wdt_keepalive();
return 0;
}
#endif /* CONFIG_PM_SLEEP */
static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume);
static const struct file_operations wdt_fops = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.open = dw_wdt_open,
.write = dw_wdt_write,
.unlocked_ioctl = dw_wdt_ioctl,
.release = dw_wdt_release
};
static struct miscdevice dw_wdt_miscdev = {
.fops = &wdt_fops,
.name = "watchdog",
.minor = WATCHDOG_MINOR,
};
static int dw_wdt_drv_probe(struct platform_device *pdev)
{
int ret;
struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem);
if (IS_ERR(dw_wdt.regs))
return PTR_ERR(dw_wdt.regs);
dw_wdt.clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(dw_wdt.clk))
return PTR_ERR(dw_wdt.clk);
ret = clk_prepare_enable(dw_wdt.clk);
if (ret)
return ret;
ret = misc_register(&dw_wdt_miscdev);
if (ret)
goto out_disable_clk;
dw_wdt.restart_handler.notifier_call = dw_wdt_restart_handle;
dw_wdt.restart_handler.priority = 128;
ret = register_restart_handler(&dw_wdt.restart_handler);
if (ret)
pr_warn("cannot register restart handler\n");
dw_wdt_set_next_heartbeat();
setup_timer(&dw_wdt.timer, dw_wdt_ping, 0);
mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
return 0;
out_disable_clk:
clk_disable_unprepare(dw_wdt.clk);
return ret;
}
static int dw_wdt_drv_remove(struct platform_device *pdev)
{
unregister_restart_handler(&dw_wdt.restart_handler);
misc_deregister(&dw_wdt_miscdev);
clk_disable_unprepare(dw_wdt.clk);
return 0;
}
#ifdef CONFIG_OF
static const struct of_device_id dw_wdt_of_match[] = {
{ .compatible = "snps,dw-wdt", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, dw_wdt_of_match);
#endif
static struct platform_driver dw_wdt_driver = {
.probe = dw_wdt_drv_probe,
.remove = dw_wdt_drv_remove,
.driver = {
.name = "dw_wdt",
.of_match_table = of_match_ptr(dw_wdt_of_match),
.pm = &dw_wdt_pm_ops,
},
};
module_platform_driver(dw_wdt_driver);
MODULE_AUTHOR("Jamie Iles");
MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver");
MODULE_LICENSE("GPL");