Message-ID: <524C79D2.5070708@overkiz.com>
Date:	Wed, 02 Oct 2013 21:53:54 +0200
From:	boris brezillon <b.brezillon@...rkiz.com>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	Wim Van Sebroeck <wim@...ana.be>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	Yang Wenyou <Wenyou.Yang@...el.com>,
	linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [v2,1/4] watchdog: at91sam9_wdt: better watchdog support

On 02/10/2013 21:34, Guenter Roeck wrote:
> On Wed, Oct 02, 2013 at 09:27:03PM +0200, boris brezillon wrote:
>> Hello Guenter,
>>
>> Thanks for reviewing this patch.
>>
>> On 02/10/2013 18:12, Guenter Roeck wrote:
>>> On Fri, Jun 21, 2013 at 03:21:28PM -0000, Boris BREZILLON wrote:
>>>> The at91sam9 watchdog timer can only be configured once, and the current
>>>> implementation tries to configure it in a static way:
>>>> - 2 seconds timeout
>>>> - wdt restart every 500ms
>>>>
>>>> If the timer has already been configured with different values, it returns an
>>>> error and do not create any watchdog device.
>>>>
>>>> This is not critical if the watchdog is disabled, but if it has been enabled with
>>>> different timeout values it will lead to a SoC reset.
>>>>
>>>> This patch series tries to address this issue by adapting the heartbeat value
>>>> according the WDT timer config:
>>>> - it first tries to configure the timer as requested.
>>>> - if it fails it fallbacks to the current config, adapting its heartbeat timer
>>>> to the needs
>>>>
>>>> This patch series also move to a dynamically allocated at91wdt device instead
>>>> of the static instance.
>>>>
>>>> It adds a new at91 wdt type: software. This new type make use of the at91 wdt
>>>> interrupt to trigger a software reboot.
>>>>
>>>> Finally it adds several properties to the device tree bindings.
>>>>
>>>> Signed-off-by: Boris BREZILLON <b.brezillon@...rkiz.com>
>>>>
>>>> ---
>>>> drivers/watchdog/at91sam9_wdt.c |  319 +++++++++++++++++++++++++++++----------
>>>>   1 file changed, 236 insertions(+), 83 deletions(-)
>>>>
>>>> diff --git a/drivers/watchdog/at91sam9_wdt.c b/drivers/watchdog/at91sam9_wdt.c
>>>> index be37dde..fb47ec5 100644
>>>> --- a/drivers/watchdog/at91sam9_wdt.c
>>>> +++ b/drivers/watchdog/at91sam9_wdt.c
>>>> @@ -19,11 +19,13 @@
>>>>   #include <linux/errno.h>
>>>>   #include <linux/init.h>
>>>> +#include <linux/interrupt.h>
>>>>   #include <linux/io.h>
>>>>   #include <linux/kernel.h>
>>>>   #include <linux/module.h>
>>>>   #include <linux/moduleparam.h>
>>>>   #include <linux/platform_device.h>
>>>> +#include <linux/reboot.h>
>>>>   #include <linux/types.h>
>>>>   #include <linux/watchdog.h>
>>>>   #include <linux/jiffies.h>
>>>> @@ -31,23 +33,32 @@
>>>>   #include <linux/bitops.h>
>>>>   #include <linux/uaccess.h>
>>>>   #include <linux/of.h>
>>>> +#include <linux/of_address.h>
>>>> +#include <linux/of_irq.h>
>>>>   #include "at91sam9_wdt.h"
>>>>   #define DRV_NAME "AT91SAM9 Watchdog"
>>>> -#define wdt_read(field) \
>>>> -	__raw_readl(at91wdt_private.base + field)
>>>> -#define wdt_write(field, val) \
>>>> -	__raw_writel((val), at91wdt_private.base + field)
>>>> +#define wdt_read(wdt, field) \
>>>> +	__raw_readl((wdt)->base + field)
>>>> +#define wdt_write(wtd, field, val) \
>>>> +	__raw_writel((val), (wdt)->base + field)
>>>>   /* AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
>>>>    * use this to convert a watchdog
>>>>    * value from/to milliseconds.
>>>>    */
>>>> +#define hz_to_ticks(h)  (((h << 8) / HZ) - 1)
>>> Unused.
>> I'll drop it.
>>
>>>> +#define ticks_to_hz(t)	(((t + 1) * HZ) >> 8)
>>>>   #define ms_to_ticks(t)	(((t << 8) / 1000) - 1)
>>>>   #define ticks_to_ms(t)	(((t + 1) * 1000) >> 8)
>>> You should put macro parameters in () to avoid undesired side effects.
>>>
>>> 	(h), (t), (field)
>>>
>>> Sure, some of them are old. No reason not to fix it, though.
>> I'll fix it (I'll fix old macros in a separate patch)
>>
>>>> +#define WDT_MR_RESET	0x3FFF2FFF
>>>> +
>>>> +#define WDT_WDD_MAX	0xFFF
>>>> +#define WDT_WDV_MAX	0xFFF
>>> What are the units ?
>> ticks (slow clk cycles).
>> I'll rename these macros:
>> #define WDT_XXX_MAX_TICKS 0xFFF
>>>> +
>>>>   /* Hardware timeout in seconds */
>>>>   #define WDT_HW_TIMEOUT 2
>>>> @@ -66,23 +77,41 @@ module_param(nowayout, bool, 0);
>>>>   MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
>>>>   	"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
>>>> -static struct watchdog_device at91_wdt_dev;
>>>> -static void at91_ping(unsigned long data);
>>>> -
>>>> -static struct {
>>>> +#define to_wdt(wdd) container_of(wdd, struct at91wdt, wdd)
>>>> +struct at91wdt {
>>>> +	struct watchdog_device wdd;
>>>>   	void __iomem *base;
>>>>   	unsigned long next_heartbeat;	/* the next_heartbeat for the timer */
>>>>   	struct timer_list timer;	/* The timer that pings the watchdog */
>>>> -} at91wdt_private;
>>>> +	u32 mr;
>>>> +	u32 mr_mask;
>>>> +	unsigned long heartbeat;	/* WDT heartbeat in jiffies */
>>>> +	bool nowayout;
>>>> +	unsigned int irq;
>>>> +};
>>>>   /* ......................................................................... */
>>>> +static irqreturn_t wdt_interrupt(int irq, void *dev_id)
>>>> +{
>>>> +	struct at91wdt *wdt = (struct at91wdt *)dev_id;
>>>> +
>>>> +	if (wdt_read(wdt, AT91_WDT_SR)) {
>>>> +		/* Reboot */
>>> That is quite obvious, isn't it ?
>> I'll drop the comment line.
>>>> +		pr_crit("at91sam9 WDT software reset\n");
>>>> +		emergency_restart();
>>>> +		pr_crit("Reboot didn't ?????\n");
>>>> +	}
>>>> +
>>>> +	return IRQ_HANDLED;
>>>> +}
>>>> +
>>>>   /*
>>>>    * Reload the watchdog timer.  (ie, pat the watchdog)
>>>>    */
>>>> -static inline void at91_wdt_reset(void)
>>>> +static inline void at91_wdt_reset(struct at91wdt *wdt)
>>>>   {
>>>> -	wdt_write(AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
>>>> +	wdt_write(wdt, AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
>>>>   }
>>>>   /*
>>>> @@ -90,26 +119,20 @@ static inline void at91_wdt_reset(void)
>>>>    */
>>>>   static void at91_ping(unsigned long data)
>>>>   {
>>>> -	if (time_before(jiffies, at91wdt_private.next_heartbeat) ||
>>>> -	    (!watchdog_active(&at91_wdt_dev))) {
>>>> -		at91_wdt_reset();
>>>> -		mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
>>>> +	struct at91wdt *wdt = (struct at91wdt *)data;
>>>> +	if (time_before(jiffies, wdt->next_heartbeat) ||
>>>> +	    (!watchdog_active(&wdt->wdd))) {
>>> 	Unnecessary () around !watchdog_active()
>>>
>>> [ Sure, old code. Not a reason not to clean it up ]
>> Okay, I'll remove all unnecessary "()" (even the old ones).
>>>> +		at91_wdt_reset(wdt);
>>>> +		mod_timer(&wdt->timer, jiffies + wdt->heartbeat);
>>>>   	} else
>>>>   		pr_crit("I will reset your machine !\n");
>>>>   }
>>>>   static int at91_wdt_ping(struct watchdog_device *wdd)
>>>>   {
>>>> +	struct at91wdt *wdt = to_wdt(wdd);
>>>>   	/* calculate when the next userspace timeout will be */
>>>> -	at91wdt_private.next_heartbeat = jiffies + wdd->timeout * HZ;
>>>> -	return 0;
>>>> -}
>>>> -
>>>> -static int at91_wdt_start(struct watchdog_device *wdd)
>>>> -{
>>>> -	/* calculate the next userspace timeout and modify the timer */
>>>> -	at91_wdt_ping(wdd);
>>>> -	mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
>>>> +	wdt->next_heartbeat = jiffies + wdd->timeout * HZ;
>>>>   	return 0;
>>>>   }
>>>> @@ -125,36 +148,82 @@ static int at91_wdt_set_timeout(struct watchdog_device *wdd, unsigned int new_ti
>>>>   	return 0;
>>>>   }
>>>> -/*
>>>> - * Set the watchdog time interval in 1/256Hz (write-once)
>>>> - * Counter is 12 bit.
>>>> - */
>>>> -static int at91_wdt_settimeout(unsigned int timeout)
>>>> +static int at91_wdt_init(struct platform_device *pdev, struct at91wdt *wdt)
>>>>   {
>>>> -	unsigned int reg;
>>>> -	unsigned int mr;
>>>> -
>>>> -	/* Check if disabled */
>>>> -	mr = wdt_read(AT91_WDT_MR);
>>>> -	if (mr & AT91_WDT_WDDIS) {
>>>> -		pr_err("sorry, watchdog is disabled\n");
>>>> -		return -EIO;
>>>> +	u32 tmp;
>>>> +	u32 delta;
>>>> +	u32 value;
>>>> +	int err;
>>>> +	u32 mask = wdt->mr_mask;
>>>> +
>>>> +	tmp = wdt_read(wdt, AT91_WDT_MR);
>>>> +	if ((tmp & mask) != (wdt->mr & mask)) {
>>>> +		if (tmp == WDT_MR_RESET) {
>>>> +			wdt_write(wdt, AT91_WDT_MR, wdt->mr);
>>>> +			tmp = wdt_read(wdt, AT91_WDT_MR);
>>>> +		}
>>>> +	}
>>>> +
>>>> +	if (tmp & AT91_WDT_WDDIS) {
>>>> +		if (wdt->mr & AT91_WDT_WDDIS)
>>>> +			return 0;
>>>> +		dev_err(wdt->wdd.parent,
>>>> +			": sorry, watchdog is disabled\n");
>>> No need to be sorry all the time. The ':' is unnecessary.
>> Sure, I'll remove the ":" and rework old and new messages (remove
>> the "sorry" word).
>>>> +		return -EINVAL;
>>>> +	}
>>>> +
>>>> +	value = tmp & AT91_WDT_WDV;
>>>> +	delta = (tmp & AT91_WDT_WDD) >> 16;
>>>> +
>>>> +	if (delta < value) {
>>>> +		if ((value / (value - delta)) < 4) {
>>> 	Unnecessary ( ) around left side of equation.
>>>
>>>> +			dev_err(wdt->wdd.parent,
>>>> +				": sorry, max-heartbeat should be at least 4 times min-heartbeat (max-heartbeat = %d x min-heartbeat)\n",
>>>> +				(value / (value - delta)));
>>> 	Unnecessary ( ) around the equation.
>>>
>>>> +			return -EINVAL;
>>>> +		}
>>>> +	}
>>>> +
>>>> +	wdt->heartbeat = ticks_to_hz(value / 4);
>>>> +
>>>> +	if (!wdt->heartbeat) {
>>>> +		dev_err(wdt->wdd.parent,
>>>> +			": sorry, linux timer (%i Hz) cannot handle watchdog timeout (%i ms)\n",
>>>> +			HZ, ticks_to_ms(value));
>>>> +		return -EINVAL;
>>> Isn't that a bit rude ? Why not set it to the minimum ?

I might have misunderstood your point.
What is a bit rude ?
  - the fact that the minimum heartbeat timeout has to be at less or 
equal to one-forth of
    max heartbeat timeout
  - the fact that heartbeat expressed in ticks has to be more than 0
  - something else
>> We're using a normal timer (not an hrtimer), and IIRC normal timers'
>> precision depends on the
>> configured HZ option. As a result the minimum heartbeat value may
>> trigger the timer function
>> after the hardware watchdog counter expires.
>>
>> An example where this problem might occur:
>>
>> HZ = 10 <=> normal timer precision = 100 ms
>> min hearbeat = 180 ms
>> max hearbeat = 200 ms
>>
> Seems to me those values are not really reasonable to start with. From a Linux
> perspective, the minimum timeout will never be less than 1 second.
>
> In the given context (HZ=10, as unlikely it might be), you might consider
> setting accepted minimum to 400ms. The maximum should then be at least 1,600ms
> anyway, correct ?

This is correct.

> Thanks,
> Guenter
>
>> The div by 4 operation is here to take a safety margin by refreshing
>> the hardware counter at least
>> 4 times more often than needed.
>>
>> I'll think of something more flexible...
>> If you have some ideas, please feel free to share it.
>>
>>>> +	}
>>>> +
>>>> +	if ((tmp & AT91_WDT_WDFIEN) && wdt->irq) {
>>>> +		err = request_irq(wdt->irq, wdt_interrupt,
>>>> +				  IRQF_SHARED | IRQF_IRQPOLL,
>>>> +				  pdev->name, wdt);
>>>> +		if (err)
>>>> +			return err;
>>>>   	}
>>>> -	/*
>>>> -	 * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
>>>> -	 *
>>>> -	 * Since WDV is a 12-bit counter, the maximum period is
>>>> -	 * 4096 / 256 = 16 seconds.
>>>> -	 */
>>>> -	reg = AT91_WDT_WDRSTEN	/* causes watchdog reset */
>>>> -		/* | AT91_WDT_WDRPROC	causes processor reset only */
>>>> -		| AT91_WDT_WDDBGHLT	/* disabled in debug mode */
>>>> -		| AT91_WDT_WDD		/* restart at any time */
>>>> -		| (timeout & AT91_WDT_WDV);  /* timer value */
>>>> -	wdt_write(AT91_WDT_MR, reg);
>>>> +	if ((tmp & wdt->mr_mask) != (wdt->mr & wdt->mr_mask))
>>>> +		dev_warn(wdt->wdd.parent,
>>>> +			 ": watchdog already configured differently (mr = %x expecting %x)\n",
>>>> +			 tmp & wdt->mr_mask, wdt->mr & wdt->mr_mask);
>>>> +
>>>> +	setup_timer(&wdt->timer, at91_ping, (unsigned long)wdt);
>>>> +	mod_timer(&wdt->timer, jiffies + wdt->heartbeat);
>>>> +
>>>> +	/* Try to set timeout from device tree first */
>>>> +	if (watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev))
>>>> +		watchdog_init_timeout(&wdt->wdd, heartbeat, &pdev->dev);
>>>> +	watchdog_set_nowayout(&wdt->wdd, wdt->nowayout);
>>>> +	err = watchdog_register_device(&wdt->wdd);
>>>> +	if (err)
>>>> +		goto out_stop_timer;
>>>> +
>>>> +	wdt->next_heartbeat = jiffies + wdt->wdd.timeout * HZ;
>>>>   	return 0;
>>>> +
>>>> +out_stop_timer:
>>>> +	del_timer(&wdt->timer);
>>>> +	return err;
>>>>   }
>>>>   /* ......................................................................... */
>>>> @@ -167,63 +236,147 @@ static const struct watchdog_info at91_wdt_info = {
>>>>   static const struct watchdog_ops at91_wdt_ops = {
>>>>   	.owner =	THIS_MODULE,
>>>> -	.start =	at91_wdt_start,
>>>> +	.start =	at91_wdt_ping,
>>>>   	.stop =		at91_wdt_stop,
>>>>   	.ping =		at91_wdt_ping,
>>>>   	.set_timeout =	at91_wdt_set_timeout,
>>>>   };
>>>> -static struct watchdog_device at91_wdt_dev = {
>>>> -	.info =		&at91_wdt_info,
>>>> -	.ops =		&at91_wdt_ops,
>>>> -	.timeout =	WDT_HEARTBEAT,
>>>> -	.min_timeout =	1,
>>>> -	.max_timeout =	0xFFFF,
>>>> -};
>>>> +#if defined(CONFIG_OF)
>>>> +static int of_at91wdt_init(struct device_node *np, struct at91wdt *wdt)
>>>> +{
>>>> +	u32 min = 0;
>>>> +	u32 max = 0xFFF;
>>> Are those default values ? If so might use defines (there are actually defines
>>> for 0xfff already).
>> I'll replace the 0xfff value by the XX_MAX macro.
>> Should I create a new XX_MIN macro ?
>>>> +	const char *tmp;
>>>> +
>>>> +	wdt->base = of_iomap(np, 0);
>>> I am a bit at loss why you need to use use this function here.
>>>
>>> I think it would be more beneficial to use devm_ioremap() or even better
>>> devm_ioremap_resource() in both of and non-dt cases; then you don't have
>>> to call iounmap().
>> Sure. This was one of my first driver using the devm and of_iomap
>> functions, and now I realize
>> I've been misusing them.
>>
>> I'll fix this too.
>>
>>>> +	if (!wdt->base) {
>>>> +		dev_err(wdt->wdd.parent, "failed to map registers, aborting.\n");
>>>> +		return -EINVAL;
>>>> +	}
>>>> +
>>>> +	/* Get the interrupts property */
>>>> +	wdt->irq = irq_of_parse_and_map(np, 0);
>>>> +	if (!wdt->irq)
>>>> +		dev_warn(wdt->wdd.parent, "failed to get IRQ from DT.\n");
>>>> +
>>>> +	if (!of_property_read_u32_index(np, "atmel,max-heartbeat-sec", 0,
>>>> +					&max)) {
>>>> +		max *= 256;
>>>> +		if (max > WDT_WDV_MAX)
>>>> +			max = WDT_WDV_MAX;
>>>> +
>>>> +		if (!of_property_read_u32_index(np, "atmel,min-heartbeat-sec",
>>>> +						0, &min)) {
>>>> +			min *= 256;
>>>> +			if (4 * min > max)
>>>> +				min = max / 4;
>>>> +		}
>>>> +	}
>>> I am a bit confused about those parameters. How do they match min_timeout and
>>> max_timeout ?
>> AT91 wdt block does not provide a reconfigurable timeout.
>> To bypass this limitation the driver periodically reset the hw
>> watchdog (based on the previous config,
>> the device tree config or the static config) using a timer.
>>
>> The ping callback (used by watchdog core) only compute the
>> next_heartbeat (expressed in system ticks)
>> based on the current jiffies value (number of ticks elapsed since
>> system startup) and the configured
>> timeout value (configured using the set_timeout callback).
>>
>> To summarize:
>>   - min/max heartbeat timeout represent the hw timeout properties
>> (those directly linked to WDD WDV
>>     fields).
>>   - min/max timeout (in watchdog_device struct) represent the
>> software timeout properties (those
>>     exposed to the user space API).
>>
>> I could rework the driver to directly use the hw properties and
>> remove the set_timeout functionality,
>> but this would break the user space API.
>>
>>>> +
>>>> +	wdt->mr_mask = 0x3FFFFFFF;
>>>> +	wdt->mr = 0;
>>>> +	if (!of_property_read_string(np, "atmel,watchdog-type", &tmp) &&
>>>> +	    !strcmp(tmp, "software")) {
>>>> +		wdt->mr |= AT91_WDT_WDFIEN;
>>>> +		wdt->mr_mask &= ~AT91_WDT_WDRPROC;
>>>> +	} else
>>>> +		wdt->mr |= AT91_WDT_WDRSTEN;
>>>> +
>>>> +	if (!of_property_read_string(np, "atmel,reset-type", &tmp) &&
>>>> +	    !strcmp(tmp, "proc"))
>>>> +		wdt->mr |= AT91_WDT_WDRPROC;
>>>> +
>>>> +	if (of_property_read_bool(np, "atmel,disable")) {
>>>> +		wdt->mr |= AT91_WDT_WDDIS;
>>>> +		wdt->mr_mask &= AT91_WDT_WDDIS;
>>>> +	}
>>>> +
>>>> +	if (of_property_read_bool(np, "atmel,idle-halt"))
>>>> +		wdt->mr |= AT91_WDT_WDIDLEHLT;
>>>> +
>>>> +	if (of_property_read_bool(np, "atmel,dbg-halt"))
>>>> +		wdt->mr |= AT91_WDT_WDDBGHLT;
>>>> +
>>>> +	wdt->mr |= max | ((max - min) << 16);
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +#else
>>>> +static inline int of_at91wdt_init(struct device_node *np, struct at91wdt *wdt)
>>>> +{
>>>> +	return 0;
>>>> +}
>>>> +#endif
>>>>   static int __init at91wdt_probe(struct platform_device *pdev)
>>>>   {
>>>>   	struct resource	*r;
>>>> -	int res;
>>>> -
>>>> -	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>>> -	if (!r)
>>>> -		return -ENODEV;
>>>> -	at91wdt_private.base = ioremap(r->start, resource_size(r));
>>>> -	if (!at91wdt_private.base) {
>>>> -		dev_err(&pdev->dev, "failed to map registers, aborting.\n");
>>>> -		return -ENOMEM;
>>>> -	}
>>>> +	int err;
>>>> +	struct at91wdt *wdt;
>>>> -	at91_wdt_dev.parent = &pdev->dev;
>>>> -	watchdog_init_timeout(&at91_wdt_dev, heartbeat, &pdev->dev);
>>>> -	watchdog_set_nowayout(&at91_wdt_dev, nowayout);
>>>> +	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
>>>> +	if (!wdt)
>>>> +		return -ENOMEM;
>>>> -	/* Set watchdog */
>>>> -	res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
>>>> -	if (res)
>>>> -		return res;
>>>> +	wdt->mr = (WDT_HW_TIMEOUT * 256) | AT91_WDT_WDRSTEN | AT91_WDT_WDD |
>>>> +		  AT91_WDT_WDDBGHLT | AT91_WDT_WDIDLEHLT;
>>>> +	wdt->mr_mask = 0x3FFFFFFF;
>>>> +	wdt->nowayout = nowayout;
>>>> +	wdt->wdd.parent = &pdev->dev;
>>>> +	wdt->wdd.info = &at91_wdt_info;
>>>> +	wdt->wdd.ops = &at91_wdt_ops;
>>>> +	wdt->wdd.timeout = WDT_HEARTBEAT;
>>>> +	wdt->wdd.min_timeout = 1;
>>>> +	wdt->wdd.max_timeout = 0xFFFF;
>>>> +
>>>> +	if (pdev->dev.of_node) {
>>>> +		err = of_at91wdt_init(pdev->dev.of_node, wdt);
>>>> +		if (err)
>>>> +			goto out_free_watchdog;
>>>> +	} else {
>>>> +		r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>>> +		if (!r) {
>>>> +			err = -ENODEV;
>>>> +			goto out_free_watchdog;
>>>> +		}
>>>> +
>>>> +		wdt->base = ioremap(r->start, resource_size(r));
>>>> +		if (!wdt->base) {
>>>> +			dev_err(&pdev->dev, "failed to map registers, aborting.\n");
>>>> +			err = -ENOMEM;
>>>> +			goto out_free_watchdog;
>>>> +		}
>>>> +	}
>>>> -	res = watchdog_register_device(&at91_wdt_dev);
>>>> -	if (res)
>>>> -		return res;
>>>> +	err = at91_wdt_init(pdev, wdt);
>>>> +	if (err)
>>>> +		goto out_iounmap;
>>>> -	at91wdt_private.next_heartbeat = jiffies + at91_wdt_dev.timeout * HZ;
>>>> -	setup_timer(&at91wdt_private.timer, at91_ping, 0);
>>>> -	mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
>>>> +	platform_set_drvdata(pdev, wdt);
>>>>   	pr_info("enabled (heartbeat=%d sec, nowayout=%d)\n",
>>>> -		at91_wdt_dev.timeout, nowayout);
>>>> +		wdt->wdd.timeout, wdt->nowayout);
>>>>   	return 0;
>>>> +
>>>> +out_iounmap:
>>>> +	iounmap(wdt->base);
>>>> +out_free_watchdog:
>>>> +	devm_kfree(&pdev->dev, wdt);
>>> The whole point of using devm_kzalloc() is that you don't have to call kfree()
>>> or devm_kfree(). So this call (and with it the label) is unnecessary.
>>>
>>>> +	return err;
>>>>   }
>>>>   static int __exit at91wdt_remove(struct platform_device *pdev)
>>>>   {
>>>> -	watchdog_unregister_device(&at91_wdt_dev);
>>>> +	struct at91wdt *wdt = platform_get_drvdata(pdev);
>>>> +	watchdog_unregister_device(&wdt->wdd);
>>>>   	pr_warn("I quit now, hardware will probably reboot!\n");
>>>> -	del_timer(&at91wdt_private.timer);
>>>> +	del_timer(&wdt->timer);
>>>> +
>>>> +	iounmap(wdt->base);
>>>> +	devm_kfree(&pdev->dev, wdt);
>>> The call to devm_kfree() is unnecessary.
>>>
>>>>   	return 0;
>>>>   }
>>

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