Re: [PATCH 3/5] watchdog: sp805: set WDOG_HW_RUNNING when appropriate

[Ray Jui]

Hi Robin,

On 5/23/2018 4:48 AM, Robin Murphy wrote:
> On 23/05/18 08:52, Scott Branden wrote:
> > On 18-05-22 04:24 PM, Ray Jui wrote:
> > > Hi Guenter,
> > >
> > > On 5/22/2018 1:54 PM, Guenter Roeck wrote:
> > > > On Tue, May 22, 2018 at 11:47:18AM -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>
> > > > > ---
> > > > > Â drivers/watchdog/sp805_wdt.c | 22 ++++++++++++++++++++++
> > > > > Â 1 file changed, 22 insertions(+)
> > > > >
> > > > > diff --git a/drivers/watchdog/sp805_wdt.c 
> > > > > b/drivers/watchdog/sp805_wdt.c
> > > > > index 1484609..408ffbe 100644
> > > > > --- a/drivers/watchdog/sp805_wdt.c
> > > > > +++ b/drivers/watchdog/sp805_wdt.c
> > > > > @@ -42,6 +42,7 @@
> > > > > ÂÂÂÂÂ /* control register masks */
> > > > > ÂÂÂÂÂ #defineÂÂÂ INT_ENABLEÂÂÂ (1 << 0)
> > > > > ÂÂÂÂÂ #defineÂÂÂ RESET_ENABLEÂÂÂ (1 << 1)
> > > > > +ÂÂÂ #defineÂÂÂ ENABLE_MASKÂÂÂ (INT_ENABLE | RESET_ENABLE)
> > > > > Â #define WDTINTCLRÂÂÂÂÂÂÂ 0x00C
> > > > > Â #define WDTRISÂÂÂÂÂÂÂÂÂÂÂ 0x010
> > > > > Â #define WDTMISÂÂÂÂÂÂÂÂÂÂÂ 0x014
> > > > > @@ -74,6 +75,18 @@ module_param(nowayout, bool, 0);
> > > > > Â MODULE_PARM_DESC(nowayout,
> > > > > ÂÂÂÂÂÂÂÂÂ "Set to 1 to keep watchdog running after device release");
> > > > > Â +/* returns true if wdt is running; otherwise returns false */
> > > > > +static bool wdt_is_running(struct watchdog_device *wdd)
> > > > > +{
> > > > > +ÂÂÂ struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
> > > > > +
> > > > > +ÂÂÂ if ((readl_relaxed(wdt->base + WDTCONTROL) & ENABLE_MASK) ==
> > > > > +ÂÂÂÂÂÂÂ ENABLE_MASK)
> > > > > +ÂÂÂÂÂÂÂ return true;
> > > > > +ÂÂÂ else
> > > > > +ÂÂÂÂÂÂÂ return false;
> > > >
> > > > ÂÂÂÂreturn !!(readl_relaxed(wdt->base + WDTCONTROL) & ENABLE_MASK));
> > >
> > > Note ENABLE_MASK contains two bits (INT_ENABLE and RESET_ENABLE); 
> > > therefore, a simple !!(expression) would not work? That is, the 
> > > masked result needs to be compared against the mask again to ensure 
> > > both bits are set, right?
> > Ray - your original code looks correct to me. Easier to read and less 
> > prone to errors as shown in the attempted translation to a single 
> > statement.
>
>  ÂÂÂÂif (<boolean condition>)
>  ÂÂÂÂÂÂÂ return true;
>  ÂÂÂÂelse
>  ÂÂÂÂÂÂÂ return false;
>
> still looks really dumb, though, and IMO is actually harder to read than 
> just "return <boolean condition>;" because it forces you to stop and 
> double-check that the logic is, in fact, only doing the obvious thing.

If you can propose a way to modify my original code above to make it 
more readable, I'm fine to make the change.

As I mentioned, I don't think the following change proposed by Guenter 
will work due to the reason I pointed out:

return !!(readl_relaxed(wdt->base + WDTCONTROL) & ENABLE_MASK));

> Robin.
>
>
>
> p.s. No thanks for making me remember the mind-boggling horror of 
> briefly maintaining part of this legacy codebase... :P
>
> $ grep -r '? true : false' --include=*.cpp . | wc -l
> 951