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

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Date:   Tue, 22 May 2018 16:24:25 -0700
From:   Ray Jui <ray.jui@...adcom.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Frank Rowand <frowand.list@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH 3/5] watchdog: sp805: set WDOG_HW_RUNNING when appropriate

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?

Thanks,

Ray