Re: [PATCH 4/6] watchdog/hpwdt: Add module parameter kdumptimeout.

[Guenter Roeck <linux@roeck-us.net>]

On Fri, May 17, 2019 at 02:59:41PM -0600, Jerry Hoemann wrote:
> Instead of unconditionally stopping the watchdog timer after receipt of
> a pretimeout NMI, reprogram the timeout based upon module parameter
> kdumptimeout.
> 
> The provides a more flexible override than the depricated allow_kdump.
> 
> Signed-off-by: Jerry Hoemann <jerry.hoemann@hpe.com>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
>  drivers/watchdog/hpwdt.c | 27 ++++++++++++++++++++++++---
>  1 file changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/watchdog/hpwdt.c b/drivers/watchdog/hpwdt.c
> index aa4101c..dc65006 100644
> --- a/drivers/watchdog/hpwdt.c
> +++ b/drivers/watchdog/hpwdt.c
> @@ -29,7 +29,8 @@
>  #define HPWDT_VERSION			"2.0.2"
>  #define SECS_TO_TICKS(secs)		((secs) * 1000 / 128)
>  #define TICKS_TO_SECS(ticks)		((ticks) * 128 / 1000)
> -#define HPWDT_MAX_TIMER			TICKS_TO_SECS(65535)
> +#define HPWDT_MAX_TICKS			65535
> +#define HPWDT_MAX_TIMER			TICKS_TO_SECS(HPWDT_MAX_TICKS)
>  #define DEFAULT_MARGIN			30
>  #define PRETIMEOUT_SEC			9
>  
> @@ -37,6 +38,7 @@
>  static unsigned int soft_margin = DEFAULT_MARGIN;	/* in seconds */
>  static bool nowayout = WATCHDOG_NOWAYOUT;
>  static bool pretimeout = IS_ENABLED(CONFIG_HPWDT_NMI_DECODING);
> +static int kdumptimeout = -1;
>  
>  static void __iomem *pci_mem_addr;		/* the PCI-memory address */
>  static unsigned long __iomem *hpwdt_nmistat;
> @@ -56,6 +58,7 @@
>  	{0},			/* terminate list */
>  };
>  
> +static struct watchdog_device hpwdt_dev;
>  /*
>   *	Watchdog operations
>   */
> @@ -94,12 +97,18 @@ static int hpwdt_stop_core(struct watchdog_device *wdd)
>  	return 0;
>  }
>  
> +static void hpwdt_ping_ticks(int val)
> +{
> +	val = min(val, HPWDT_MAX_TICKS);
> +	iowrite16(val, hpwdt_timer_reg);
> +}
> +
>  static int hpwdt_ping(struct watchdog_device *wdd)
>  {
>  	int reload = SECS_TO_TICKS(min(wdd->timeout, wdd->max_hw_heartbeat_ms/1000));
>  
>  	dev_dbg(wdd->parent, "ping  watchdog 0x%08x:0x%08x\n", wdd->timeout, reload);
> -	iowrite16(reload, hpwdt_timer_reg);
> +	hpwdt_ping_ticks(reload);
>  
>  	return 0;
>  }
> @@ -175,7 +184,14 @@ static int hpwdt_pretimeout(unsigned int ulReason, struct pt_regs *regs)
>  	if (ilo5 && !pretimeout && !mynmi)
>  		return NMI_DONE;
>  
> -	hpwdt_stop();
> +	if (kdumptimeout < 0)
> +		hpwdt_stop();
> +	else if (kdumptimeout == 0)
> +		;
> +	else {
> +		unsigned int val = max((unsigned int)kdumptimeout, hpwdt_dev.timeout);
> +		hpwdt_ping_ticks(SECS_TO_TICKS(val));
> +	}
>  
>  	hex_byte_pack(panic_msg, mynmi);
>  	nmi_panic(regs, panic_msg);
> @@ -328,6 +344,7 @@ static int hpwdt_init_one(struct pci_dev *dev,
>  		pretimeout = 0;
>  	}
>  	hpwdt_dev.pretimeout = pretimeout ? PRETIMEOUT_SEC : 0;
> +	kdumptimeout = min(kdumptimeout, HPWDT_MAX_TIMER);
>  
>  	hpwdt_dev.parent = &dev->dev;
>  	retval = watchdog_register_device(&hpwdt_dev);
> @@ -342,6 +359,7 @@ static int hpwdt_init_one(struct pci_dev *dev,
>  				hpwdt_dev.timeout, nowayout);
>  	dev_info(&dev->dev, "pretimeout: %s.\n",
>  				pretimeout ? "on" : "off");
> +	dev_info(&dev->dev, "kdumptimeout: %d.\n", kdumptimeout);
>  
>  	if (dev->subsystem_vendor == PCI_VENDOR_ID_HP_3PAR)
>  		ilo5 = true;
> @@ -387,6 +405,9 @@ static void hpwdt_exit(struct pci_dev *dev)
>  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
>  		__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
>  
> +module_param(kdumptimeout, int, 0444);
> +MODULE_PARM_DESC(kdumptimeout, "Timeout applied for crash kernel transition in seconds");
> +
>  #ifdef CONFIG_HPWDT_NMI_DECODING
>  module_param(pretimeout, bool, 0);
>  MODULE_PARM_DESC(pretimeout, "Watchdog pretimeout enabled");