Subject: Re: [PATCH] watchdog: mpc8xxx: use the core worker function

From: Guenter Roeck <[email-masked]>
Date: Tue, 7 Nov 2017 14:56:04 -0800

On Tue, Nov 07, 2017 at 05:23:56PM +0100, Christophe Leroy wrote:
> The watchdog core includes a worker function which pings the
> watchdog until user app starts pinging it and which also
> pings it if the HW require more frequent pings.
> Use that function instead of the dedicated timer.
> In the mean time, we can allow the user to change the timeout.
> 
> Then change the timeout module parameter to use seconds and
> use the watchdog_init_timeout() core function.
> 
> On some HW (eg: the 8xx), SWCRR contains bits unrelated to the
> watchdog which have to be preserved upon write.
> 
> This driver has nothing preventing the use of the magic close, so
> enable it.
> 
> Signed-off-by: Christophe Leroy <[email-masked]>
> ---
>  drivers/watchdog/mpc8xxx_wdt.c | 86 ++++++++++++++++++++----------------------
>  1 file changed, 40 insertions(+), 46 deletions(-)
> 
> diff --git a/drivers/watchdog/mpc8xxx_wdt.c b/drivers/watchdog/mpc8xxx_wdt.c
> index 366e5c7e650b..c2ac4b6b1253 100644
> --- a/drivers/watchdog/mpc8xxx_wdt.c
> +++ b/drivers/watchdog/mpc8xxx_wdt.c
> @@ -22,7 +22,6 @@
>  #include <linux/fs.h>
>  #include <linux/init.h>
>  #include <linux/kernel.h>
> -#include <linux/timer.h>
>  #include <linux/of_address.h>
>  #include <linux/of_platform.h>
>  #include <linux/module.h>
> @@ -31,10 +30,13 @@
>  #include <linux/uaccess.h>
>  #include <sysdev/fsl_soc.h>
>  
> +#define WATCHDOG_TIMEOUT 10
> +
>  struct mpc8xxx_wdt {
>  	__be32 res0;
>  	__be32 swcrr; /* System watchdog control register */
>  #define SWCRR_SWTC 0xFFFF0000 /* Software Watchdog Time Count. */
> +#define SWCRR_SWF  0x00000008 /* Software Watchdog Freeze (mpc8xx). */
>  #define SWCRR_SWEN 0x00000004 /* Watchdog Enable bit. */
>  #define SWCRR_SWRI 0x00000002 /* Software Watchdog Reset/Interrupt Select bit.*/
>  #define SWCRR_SWPR 0x00000001 /* Software Watchdog Counter Prescale bit. */
> @@ -52,14 +54,15 @@ struct mpc8xxx_wdt_type {
>  struct mpc8xxx_wdt_ddata {
>  	struct mpc8xxx_wdt __iomem *base;
>  	struct watchdog_device wdd;
> -	struct timer_list timer;
>  	spinlock_t lock;
> +	int prescaler;
>  };
>  
> -static u16 timeout = 0xffff;
> +static u16 timeout;
>  module_param(timeout, ushort, 0);
>  MODULE_PARM_DESC(timeout,
> -	"Watchdog timeout in ticks. (0<timeout<65536, default=65535)");
> +	"Watchdog timeout in seconds. (1<timeout<65535, default="
> +	__MODULE_STRING(WATCHDOG_TIMEOUT) ")");
>  
>  static bool reset = 1;
>  module_param(reset, bool, 0);
> @@ -80,31 +83,35 @@ static void mpc8xxx_wdt_keepalive(struct mpc8xxx_wdt_ddata *ddata)
>  	spin_unlock(&ddata->lock);
>  }
>  
> -static void mpc8xxx_wdt_timer_ping(unsigned long arg)
> -{
> -	struct mpc8xxx_wdt_ddata *ddata = (void *)arg;
> -
> -	mpc8xxx_wdt_keepalive(ddata);
> -	/* We're pinging it twice faster than needed, just to be sure. */
> -	mod_timer(&ddata->timer, jiffies + HZ * ddata->wdd.timeout / 2);
> -}
> -
>  static int mpc8xxx_wdt_start(struct watchdog_device *w)
>  {
>  	struct mpc8xxx_wdt_ddata *ddata =
>  		container_of(w, struct mpc8xxx_wdt_ddata, wdd);
> -
> -	u32 tmp = SWCRR_SWEN | SWCRR_SWPR;
> +	u32 tmp;
> +	u32 timeout;
>  
>  	/* Good, fire up the show */
> +	tmp = in_be32(&ddata->base->swcrr);
> +	tmp &= ~(SWCRR_SWTC | SWCRR_SWF | SWCRR_SWEN | SWCRR_SWRI | SWCRR_SWPR);
> +	tmp |= SWCRR_SWEN | SWCRR_SWPR;
> +
>  	if (reset)
>  		tmp |= SWCRR_SWRI;
>  
> -	tmp |= timeout << 16;
> +	timeout = ddata->wdd.timeout * fsl_get_sys_freq() / ddata->prescaler;
> +	tmp |= min(timeout, 0xffffU) << 16;
>  
>  	out_be32(&ddata->base->swcrr, tmp);
>  
> -	del_timer_sync(&ddata->timer);
> +	tmp = in_be32(&ddata->base->swcrr);
> +	if (!(tmp & SWCRR_SWEN))
> +		return -EOPNOTSUPP;
> +
> +	ddata->wdd.max_hw_heartbeat_ms = ((tmp >> 16) * ddata->prescaler) /
> +					 (fsl_get_sys_freq() / 1000);
> +	ddata->wdd.min_timeout = ddata->wdd.max_hw_heartbeat_ms / 1000;

That is odd. Why set the minimum timeout period to the maximum hardware
timeout, rounded down to a full second ?

Note that it is wrong to set the values for min_timeout and
max_hw_heartbeat_ms in the _start function; they should be set
in the probe function. The start function should also not update
ddata->wdd.timeout; that should happen in set_timeout if supported,
or in probe.

> +	if (ddata->wdd.timeout < ddata->wdd.min_timeout)
> +		ddata->wdd.timeout = ddata->wdd.min_timeout;
>  
>  	return 0;
>  }
> @@ -118,17 +125,8 @@ static int mpc8xxx_wdt_ping(struct watchdog_device *w)
>  	return 0;
>  }
>  
> -static int mpc8xxx_wdt_stop(struct watchdog_device *w)
> -{
> -	struct mpc8xxx_wdt_ddata *ddata =
> -		container_of(w, struct mpc8xxx_wdt_ddata, wdd);
> -
> -	mod_timer(&ddata->timer, jiffies);
> -	return 0;
> -}
> -
>  static struct watchdog_info mpc8xxx_wdt_info = {
> -	.options = WDIOF_KEEPALIVEPING,
> +	.options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT,
>  	.firmware_version = 1,
>  	.identity = "MPC8xxx",
>  };
> @@ -137,7 +135,6 @@ static struct watchdog_ops mpc8xxx_wdt_ops = {
>  	.owner = THIS_MODULE,
>  	.start = mpc8xxx_wdt_start,
>  	.ping = mpc8xxx_wdt_ping,
> -	.stop = mpc8xxx_wdt_stop,

That means the watchdog can not be stopped ?

>  };
>  
>  static int mpc8xxx_wdt_probe(struct platform_device *ofdev)
> @@ -148,7 +145,6 @@ static int mpc8xxx_wdt_probe(struct platform_device *ofdev)
>  	struct mpc8xxx_wdt_ddata *ddata;
>  	u32 freq = fsl_get_sys_freq();
>  	bool enabled;
> -	unsigned int timeout_sec;
>  
>  	wdt_type = of_device_get_match_data(&ofdev->dev);
>  	if (!wdt_type)
> @@ -173,35 +169,34 @@ static int mpc8xxx_wdt_probe(struct platform_device *ofdev)
>  	}
>  
>  	spin_lock_init(&ddata->lock);
> -	setup_timer(&ddata->timer, mpc8xxx_wdt_timer_ping,
> -		    (unsigned long)ddata);
>  
>  	ddata->wdd.info = &mpc8xxx_wdt_info,
>  	ddata->wdd.ops = &mpc8xxx_wdt_ops,
>  
> -	/* Calculate the timeout in seconds */
> -	timeout_sec = (timeout * wdt_type->prescaler) / freq;
> -
> -	ddata->wdd.timeout = timeout_sec;
> +	ddata->wdd.timeout = WATCHDOG_TIMEOUT;
> +	watchdog_init_timeout(&ddata->wdd, timeout, &ofdev->dev);
> +	ddata->prescaler = wdt_type->prescaler;
>  
>  	watchdog_set_nowayout(&ddata->wdd, nowayout);
>  
> +	/*
> +	 * If the watchdog was previously enabled or we're running on
> +	 * MPC8xxx, we should ping the wdt from the kernel until the
> +	 * userspace handles it.
> +	 */
> +	if (enabled) {
> +		mpc8xxx_wdt_start(&ddata->wdd);
> +		set_bit(WDOG_HW_RUNNING, &ddata->wdd.status);
> +	}
> +
>  	ret = watchdog_register_device(&ddata->wdd);
>  	if (ret) {
>  		pr_err("cannot register watchdog device (err=%d)\n", ret);
>  		return ret;
>  	}
>  
> -	pr_info("WDT driver for MPC8xxx initialized. mode:%s timeout=%d (%d seconds)\n",
> -		reset ? "reset" : "interrupt", timeout, timeout_sec);
> -
> -	/*
> -	 * If the watchdog was previously enabled or we're running on
> -	 * MPC8xxx, we should ping the wdt from the kernel until the
> -	 * userspace handles it.
> -	 */
> -	if (enabled)
> -		mod_timer(&ddata->timer, jiffies);
> +	pr_info("WDT driver for MPC8xxx initialized. mode:%s timeout=%d sec\n",
> +		reset ? "reset" : "interrupt", ddata->wdd.timeout);
>  
>  	platform_set_drvdata(ofdev, ddata);
>  	return 0;
> @@ -213,7 +208,6 @@ static int mpc8xxx_wdt_remove(struct platform_device *ofdev)
>  
>  	pr_crit("Watchdog removed, expect the %s soon!\n",
>  		reset ? "reset" : "machine check exception");
> -	del_timer_sync(&ddata->timer);
>  	watchdog_unregister_device(&ddata->wdd);
>  
>  	return 0;
> -- 
> 2.13.3
>