Subject: [PATCH 1/4] watchdog: at91sam9_wdt: better watchdog support

From: [email-masked] (boris brezillon)
Date: Thu, 03 Oct 2013 19:55:04 +0200

Hi Guenter,

On 03/10/2013 19:31, Guenter Roeck wrote:
> On Thu, Oct 03, 2013 at 02:19:18PM +0200, 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 <[email-masked]>
> Hi Boris,
>
> deeper dive this time ...
>
>> ---
>>   drivers/watchdog/at91sam9_wdt.c |  300 ++++++++++++++++++++++++++++-----------
>>   1 file changed, 217 insertions(+), 83 deletions(-)
>>
>> diff --git a/drivers/watchdog/at91sam9_wdt.c b/drivers/watchdog/at91sam9_wdt.c
>> index be37dde..8f44528 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>
>> @@ -31,22 +33,33 @@
>>   #include <linux/bitops.h>
>>   #include <linux/uaccess.h>
>>   #include <linux/of.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 ms_to_ticks(t)	(((t << 8) / 1000) - 1)
>> -#define ticks_to_ms(t)	(((t + 1) * 1000) >> 8)
>> +#define ticks_to_hz_rounddown(t)	((((t) + 1) * HZ) >> 8)
>> +#define ticks_to_hz_roundup(t)		(((((t) + 1) * HZ) + 255) >> 8)
>> +#define ticks_to_secs(t)		(((t) + 1) >> 8)
>> +#define secs_to_ticks(s)		(((s) << 8) - 1)
>> +
>> +#define WDT_MR_RESET	0x3FFF2FFF
>> +
>> +/* Watchdog max counter value in ticks */
>> +#define WDT_COUNTER_MAX_TICKS	0xFFF
>> +
>> +/* Watchdog max delta/value in secs */
>> +#define WDT_COUNTER_MAX_SECS	ticks_to_secs(WDT_COUNTER_MAX_TICKS)
>>   
>>   /* Hardware timeout in seconds */
>>   #define WDT_HW_TIMEOUT 2
>> @@ -66,23 +79,40 @@ 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)) {
>> +		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 +120,20 @@ 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)) {
>> +		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 +149,84 @@ static int at91_wdt_set_timeout(struct watchdog_device *wdd, unsigned int new_ti
> at91_wdt_set_timeout only sets the new timeout but does not update
> next_heartbeat. That is ok if the timeout decreases, but if it is
> increased (say, from 1 second to 1 minute) it might result in a missed
> ping as userspace will subsequently believe that the new (larger)
> timeout was accepted by the driver. So I think you should also call
> at91_wdt_ping here or set wdt->next_heartbeat directly.
Absolutely, I'll call at91_wdt_ping (or start as it will be renamed).

>>   	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;
>> +	unsigned long min_heartbeat = 1;
>> +
>> +	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);
>> +		}
>>   	}
>>   
>> -	/*
>> -	 * 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 & AT91_WDT_WDDIS) {
>> +		if (wdt->mr & AT91_WDT_WDDIS)
>> +			return 0;
>> +		dev_err(wdt->wdd.parent, "watchdog is disabled\n");
> Took me a while to get why you use "wdt->wdd.parent" :).
> I would just have passed the 'dev' argument. Your call, though.

I can't use wdt->wdd.dev, because the watchdog device is not registered yet,
but I can use &pdev->dev instead.
What do you prefer ?

>> +		return -EINVAL;
>> +	}
>> +
>> +	value = tmp & AT91_WDT_WDV;
>> +	delta = (tmp & AT91_WDT_WDD) >> 16;
>> +
>> +	if (delta < value)
>> +		min_heartbeat = ticks_to_hz_roundup(value - delta);
>> +
>> +	wdt->heartbeat = ticks_to_hz_rounddown(value);
>> +	if (!wdt->heartbeat) {
>> +		dev_err(wdt->wdd.parent,
>> +			"heartbeat is too small for the system to handle it correctly\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (wdt->heartbeat < min_heartbeat + 3) {
>> +		wdt->heartbeat = min_heartbeat;
>> +		dev_warn(wdt->wdd.parent,
>> +			 "min heartbeat and max heartbeat might be too close for the system to handle it correctly\n");
>> +		if (wdt->heartbeat < 4)
>> +			dev_warn(wdt->wdd.parent,
>> +				 "heartbeat might be too small for the system to handle it correctly\n");
>> +	} else
>> +		wdt->heartbeat -= 4;
> That means heartbeat can be 0, correct (if min_heartbeat == 1) ?
Yes, this is a mistake. It should be

if (wdt->heartbeat < min_heartbeat + 4) {
...
}

> Will that work ?
Absolutely not :)
I'll fix 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;
>> +	}
>> +
>> +	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 +239,125 @@ 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,
> Notpick, but you don't need both start and ping. If both are the same, providing
> start is sufficient. Given this, it might be cleaner to name the function
> at91_wdt_start and not provide ping.
I'll change this too.

Thanks, for catching these bugs.

Regards,

Boris

>>   	.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 = WDT_COUNTER_MAX_SECS;
>> +	const char *tmp;
>> +
>> +	/* 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)) {
>> +		if (!max || max > WDT_COUNTER_MAX_SECS)
>> +			max = WDT_COUNTER_MAX_SECS;
>> +
>> +		if (!of_property_read_u32_index(np, "atmel,min-heartbeat-sec",
>> +						0, &min)) {
>> +			if (min >= max)
>> +				min = max - 1;
>> +		}
>> +	}
>> +
>> +	min = secs_to_ticks(min);
>> +	max = secs_to_ticks(max);
>> +
>> +	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;
>> +	int err;
>> +	struct at91wdt *wdt;
>>   
>> -	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");
>> +	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
>> +	if (!wdt)
>>   		return -ENOMEM;
>> -	}
>>   
>> -	at91_wdt_dev.parent = &pdev->dev;
>> -	watchdog_init_timeout(&at91_wdt_dev, heartbeat, &pdev->dev);
>> -	watchdog_set_nowayout(&at91_wdt_dev, nowayout);
>> +	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;
>>   
>> -	/* Set watchdog */
>> -	res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
>> -	if (res)
>> -		return res;
>> +	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +	wdt->base = devm_ioremap_resource(&pdev->dev, r);
>> +	if (IS_ERR(wdt->base))
>> +		return PTR_ERR(wdt->base);
>> +
>> +	if (pdev->dev.of_node) {
>> +		err = of_at91wdt_init(pdev->dev.of_node, wdt);
>> +		if (err)
>> +			return err;
>> +	}
>>   
>> -	res = watchdog_register_device(&at91_wdt_dev);
>> -	if (res)
>> -		return res;
>> +	err = at91_wdt_init(pdev, wdt);
>> +	if (err)
>> +		return err;
>>   
>> -	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;
>>   }
>>   
>>   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);
>>   
>>   	return 0;
>>   }
>> -- 
>> 1.7.9.5
>>
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