Messages in this thread | | | Subject | Re: [PATCH 3/5] watchdog: sp805: set WDOG_HW_RUNNING when appropriate | From | Robin Murphy <> | Date | Wed, 23 May 2018 18:15:14 +0100 |
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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@broadcom.com> >>>>>> Reviewed-by: Vladimir Olovyannikov >>>>>> <vladimir.olovyannikov@broadcom.com> >>>>>> Reviewed-by: Scott Branden <scott.branden@broadcom.com> >>>>>> --- >>>>>> 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;
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 ;)
Robin.
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