linux-kernel - Re: [PATCH 3/5] watchdog: sp805: set WDOG_HW

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Message-ID: <76d47e02-7a5f-3fc2-3905-cd4aa03ac69c@arm.com>
Date:   Wed, 23 May 2018 12:48:10 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Scott Branden <scott.branden@...adcom.com>,
        Ray Jui <ray.jui@...adcom.com>,
        Guenter Roeck <linux@...ck-us.net>
Cc:     Mark Rutland <mark.rutland@....com>, devicetree@...r.kernel.org,
        linux-watchdog@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Frank Rowand <frowand.list@...il.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/5] watchdog: sp805: set WDOG_HW_RUNNING when appropriate

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@...adcom.com>
>>>> Reviewed-by: Vladimir Olovyannikov <vladimir.olovyannikov@...adcom.com>
>>>> Reviewed-by: Scott Branden <scott.branden@...adcom.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.

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