Re: [PATCH v3 4/6] watchdog: sp805: set WDOG_HW_RUNNING when appropriate

[Ray Jui]

On 5/24/2018 9:19 AM, Guenter Roeck wrote:
> On Wed, May 23, 2018 at 05:15:22PM -0700, Ray Jui wrote:
> > If the watchdog hardware is already enabled during the boot process,
> > when the Linux watchdog driver loads, it should reset the watchdog and
> > tell the watchdog framework. As a result, ping can be generated from
> > the watchdog framework, until the userspace watchdog daemon takes over
> > control
> >
> > Signed-off-by: Ray Jui <ray.jui@xxxxxxxxxxxx>
> > Reviewed-by: Vladimir Olovyannikov <vladimir.olovyannikov@xxxxxxxxxxxx>
> > Reviewed-by: Scott Branden <scott.branden@xxxxxxxxxxxx>
>
> Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
>
> I have one question, though: Is it really correct that both
> INT_ENABLE _and_ RESET_ENABLE have to be set to enable the watdog ?
> What if only RESET_ENABLE is set ?

According to the SP805 TRM, INT_ENABLE needs to be set to high to enable 
the counter and the interrupt. Counter will be stopped if INT_ENABLE is 
cleared. So yes, INT_ENABLE needs to be set.

Thanks,

Ray

> Thanks,
> Guenter
>
> > ---
> >   drivers/watchdog/sp805_wdt.c | 19 +++++++++++++++++++
> >   1 file changed, 19 insertions(+)
> >
> > diff --git a/drivers/watchdog/sp805_wdt.c b/drivers/watchdog/sp805_wdt.c
> > index 1484609..d662a6f 100644
> > --- a/drivers/watchdog/sp805_wdt.c
> > +++ b/drivers/watchdog/sp805_wdt.c
> > @@ -42,6 +42,7 @@
> >   	/* control register masks */
> >   	#define	INT_ENABLE	(1 << 0)
> >   	#define	RESET_ENABLE	(1 << 1)
> > +	#define	ENABLE_MASK	(INT_ENABLE | RESET_ENABLE)
> >   #define WDTINTCLR		0x00C
> >   #define WDTRIS			0x010
> >   #define WDTMIS			0x014
> > @@ -74,6 +75,15 @@ module_param(nowayout, bool, 0);
> >   MODULE_PARM_DESC(nowayout,
> >   		"Set to 1 to keep watchdog running after device release");
> >   
> > +/* returns true if wdt is running; otherwise returns false */
> > +static bool wdt_is_running(struct watchdog_device *wdd)
> > +{
> > +	struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
> > +	u32 wdtcontrol = readl_relaxed(wdt->base + WDTCONTROL);
> > +
> > +	return (wdtcontrol & ENABLE_MASK) == ENABLE_MASK;
> > +}
> > +
> >   /* This routine finds load value that will reset system in required timout */
> >   static int wdt_setload(struct watchdog_device *wdd, unsigned int timeout)
> >   {
> > @@ -239,6 +249,15 @@ sp805_wdt_probe(struct amba_device *adev, const struct amba_id *id)
> >   	watchdog_init_timeout(&wdt->wdd, 0, &adev->dev);
> >   	wdt_setload(&wdt->wdd, wdt->wdd.timeout);
> >   
> > +	/*
> > +	 * If HW is already running, enable/reset the wdt and set the running
> > +	 * bit to tell the wdt subsystem
> > +	 */
> > +	if (wdt_is_running(&wdt->wdd)) {
> > +		wdt_enable(&wdt->wdd);
> > +		set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
> > +	}
> > +
> >   	ret = watchdog_register_device(&wdt->wdd);
> >   	if (ret) {
> >   		dev_err(&adev->dev, "watchdog_register_device() failed: %d\n",
> > --
> > 2.1.4
> >
> > --
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