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

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Date:   Wed, 23 May 2018 00:52:27 -0700
From:   Scott Branden <scott.branden@...adcom.com>
To:     Ray Jui <ray.jui@...adcom.com>, 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



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.
>
> Thanks,
>
> Ray