linux/drivers/watchdog/dw_wdt.c
Guenter Roeck c97344f73f watchdog: dw_wdt: Read clock rate only once and validate it
Coverity reports:

divide_by_zero: In expression readl(dw_wdt->regs + 8) /
clk_get_rate(dw_wdt->clk), division by expression clk_get_rate(dw_wdt->clk)
which may be zero has undefined behavior.

The clock used for the watchdog timer won't change its rate, so read it
only once during probe. Also validate it and abort the probe function
with an error if it is 0.

Cc: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
2016-09-23 08:40:55 +02:00

319 lines
8.1 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
* do not implement a stop function. The watchdog core will continue to send
* heartbeat requests after the watchdog device has been closed.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/kernel.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/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) ")");
struct dw_wdt {
void __iomem *regs;
struct clk *clk;
unsigned long rate;
struct notifier_block restart_handler;
struct watchdog_device wdd;
};
#define to_dw_wdt(wdd) container_of(wdd, struct dw_wdt, wdd)
static inline int dw_wdt_is_enabled(struct dw_wdt *dw_wdt)
{
return readl(dw_wdt->regs + WDOG_CONTROL_REG_OFFSET) &
WDOG_CONTROL_REG_WDT_EN_MASK;
}
static inline int dw_wdt_top_in_seconds(struct dw_wdt *dw_wdt, 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 (1U << (16 + top)) / dw_wdt->rate;
}
static int dw_wdt_get_top(struct dw_wdt *dw_wdt)
{
int top = readl(dw_wdt->regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF;
return dw_wdt_top_in_seconds(dw_wdt, top);
}
static int dw_wdt_ping(struct watchdog_device *wdd)
{
struct dw_wdt *dw_wdt = to_dw_wdt(wdd);
writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt->regs +
WDOG_COUNTER_RESTART_REG_OFFSET);
return 0;
}
static int dw_wdt_set_timeout(struct watchdog_device *wdd, unsigned int top_s)
{
struct dw_wdt *dw_wdt = to_dw_wdt(wdd);
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(dw_wdt, 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);
wdd->timeout = dw_wdt_top_in_seconds(dw_wdt, top_val);
return 0;
}
static int dw_wdt_start(struct watchdog_device *wdd)
{
struct dw_wdt *dw_wdt = to_dw_wdt(wdd);
dw_wdt_set_timeout(wdd, wdd->timeout);
set_bit(WDOG_HW_RUNNING, &wdd->status);
writel(WDOG_CONTROL_REG_WDT_EN_MASK,
dw_wdt->regs + WDOG_CONTROL_REG_OFFSET);
return 0;
}
static int dw_wdt_restart_handle(struct notifier_block *this,
unsigned long mode, void *cmd)
{
struct dw_wdt *dw_wdt;
u32 val;
dw_wdt = container_of(this, struct dw_wdt, restart_handler);
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 unsigned int dw_wdt_get_timeleft(struct watchdog_device *wdd)
{
struct dw_wdt *dw_wdt = to_dw_wdt(wdd);
return readl(dw_wdt->regs + WDOG_CURRENT_COUNT_REG_OFFSET) /
dw_wdt->rate;
}
static const struct watchdog_info dw_wdt_ident = {
.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
WDIOF_MAGICCLOSE,
.identity = "Synopsys DesignWare Watchdog",
};
static const struct watchdog_ops dw_wdt_ops = {
.owner = THIS_MODULE,
.start = dw_wdt_start,
.ping = dw_wdt_ping,
.set_timeout = dw_wdt_set_timeout,
.get_timeleft = dw_wdt_get_timeleft,
};
#ifdef CONFIG_PM_SLEEP
static int dw_wdt_suspend(struct device *dev)
{
struct dw_wdt *dw_wdt = dev_get_drvdata(dev);
clk_disable_unprepare(dw_wdt->clk);
return 0;
}
static int dw_wdt_resume(struct device *dev)
{
struct dw_wdt *dw_wdt = dev_get_drvdata(dev);
int err = clk_prepare_enable(dw_wdt->clk);
if (err)
return err;
dw_wdt_ping(&dw_wdt->wdd);
return 0;
}
#endif /* CONFIG_PM_SLEEP */
static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume);
static int dw_wdt_drv_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct watchdog_device *wdd;
struct dw_wdt *dw_wdt;
struct resource *mem;
int ret;
dw_wdt = devm_kzalloc(dev, sizeof(*dw_wdt), GFP_KERNEL);
if (!dw_wdt)
return -ENOMEM;
mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
dw_wdt->regs = devm_ioremap_resource(dev, mem);
if (IS_ERR(dw_wdt->regs))
return PTR_ERR(dw_wdt->regs);
dw_wdt->clk = devm_clk_get(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;
dw_wdt->rate = clk_get_rate(dw_wdt->clk);
if (dw_wdt->rate == 0) {
ret = -EINVAL;
goto out_disable_clk;
}
wdd = &dw_wdt->wdd;
wdd->info = &dw_wdt_ident;
wdd->ops = &dw_wdt_ops;
wdd->min_timeout = 1;
wdd->max_hw_heartbeat_ms =
dw_wdt_top_in_seconds(dw_wdt, DW_WDT_MAX_TOP) * 1000;
wdd->parent = dev;
watchdog_set_drvdata(wdd, dw_wdt);
watchdog_set_nowayout(wdd, nowayout);
watchdog_init_timeout(wdd, 0, dev);
/*
* If the watchdog is already running, use its already configured
* timeout. Otherwise use the default or the value provided through
* devicetree.
*/
if (dw_wdt_is_enabled(dw_wdt)) {
wdd->timeout = dw_wdt_get_top(dw_wdt);
set_bit(WDOG_HW_RUNNING, &wdd->status);
} else {
wdd->timeout = DW_WDT_DEFAULT_SECONDS;
watchdog_init_timeout(wdd, 0, dev);
}
platform_set_drvdata(pdev, dw_wdt);
ret = watchdog_register_device(wdd);
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");
return 0;
out_disable_clk:
clk_disable_unprepare(dw_wdt->clk);
return ret;
}
static int dw_wdt_drv_remove(struct platform_device *pdev)
{
struct dw_wdt *dw_wdt = platform_get_drvdata(pdev);
unregister_restart_handler(&dw_wdt->restart_handler);
watchdog_unregister_device(&dw_wdt->wdd);
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");