On Wed, May 23, 2018 at 06:15:14PM +0100, Robin Murphy wrote:
> On 23/05/18 17:29, Ray Jui wrote:
> >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>
> >>>>>>---
> >>>>>> drivers/watchdog/sp805_wdt.c | 22 ++++++++++++++++++++++
> >>>>>> 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 @@
> >>>>>> /* 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 +75,18 @@ 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);
> >>>>>>+
> >>>>>>+ if ((readl_relaxed(wdt->base + WDTCONTROL) & ENABLE_MASK) ==
> >>>>>>+ ENABLE_MASK)
> >>>>>>+ return true;
> >>>>>>+ else
> >>>>>>+ return false;
> >>>>>
> >>>>> return !!(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.
> >>
> >> if (<boolean condition>)
> >> return true;
> >> else
> >> 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.
>
> Well,
>
> return readl_relaxed(wdt->base + WDTCONTROL) & ENABLE_MASK == ENABLE_MASK;
>
> would probably be reasonable to anyone other than the 80-column zealots, but
> removing the silly boolean-to-boolean translation idiom really only
> emphasises the fact that it's fundamentally a big complex statement; for
> maximum clarity I'd be inclined to separate the two logical operations (read
> and comparison), e.g.:
>
> u32 wdtcontrol = readl_relaxed(wdt->base + WDTCONTROL);
>
> return wdtcontrol & ENABLE_MASK == ENABLE_MASK;
== has higher precendence than bitwise &, so this will need ( ),
but otherwise I agree.
>
> which is still -3 lines vs. the original.
>
> >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));
>
> FWIW, getting the desired result should only need one logical not swapping
> for a bitwise one there:
>
> return !(~readl_relaxed(wdt->base + WDTCONTROL) & ENABLE_MASK);
>
> but that's well into "too clever for its own good" territory ;)
Yes, that would be confusing.
>
> Robin.
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
