linux-kernel - Re: [PATCH v2 3/8] watchdog: JZ4740: Register a restart handler

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Date:   Sat, 20 Jan 2018 07:45:46 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>,
        Paul Cercueil <paul@...pouillou.net>
Cc:     Ralf Baechle <ralf@...ux-mips.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Wim Van Sebroeck <wim@...ana.be>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux-MIPS <linux-mips@...ux-mips.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-watchdog@...r.kernel.org
Subject: Re: [PATCH v2 3/8] watchdog: JZ4740: Register a restart handler

On 01/19/2018 11:31 PM, PrasannaKumar Muralidharan wrote:
> Hi Paul,
> 
> On 30 December 2017 at 19:21, Paul Cercueil <paul@...pouillou.net> wrote:
>> The watchdog driver can restart the system by simply configuring the
>> hardware for a timeout of 0 seconds.
>>
>> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
>> Reviewed-by: Guenter Roeck <linux@...ck-us.net>
>> ---
>>   drivers/watchdog/jz4740_wdt.c | 9 +++++++++
>>   1 file changed, 9 insertions(+)
>>
>>   v2: No change
>>
>> diff --git a/drivers/watchdog/jz4740_wdt.c b/drivers/watchdog/jz4740_wdt.c
>> index 92d6ca8ceb49..fa7f49a3212c 100644
>> --- a/drivers/watchdog/jz4740_wdt.c
>> +++ b/drivers/watchdog/jz4740_wdt.c
>> @@ -130,6 +130,14 @@ static int jz4740_wdt_stop(struct watchdog_device *wdt_dev)
>>          return 0;
>>   }
>>
>> +static int jz4740_wdt_restart(struct watchdog_device *wdt_dev,
>> +                             unsigned long action, void *data)
>> +{
>> +       wdt_dev->timeout = 0;
>> +       jz4740_wdt_start(wdt_dev);
>> +       return 0;
>> +}
>> +
>>   static const struct watchdog_info jz4740_wdt_info = {
>>          .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
>>          .identity = "jz4740 Watchdog",
>> @@ -141,6 +149,7 @@ static const struct watchdog_ops jz4740_wdt_ops = {
>>          .stop = jz4740_wdt_stop,
>>          .ping = jz4740_wdt_ping,
>>          .set_timeout = jz4740_wdt_set_timeout,
>> +       .restart = jz4740_wdt_restart,
>>   };
>>
>>   #ifdef CONFIG_OF
>> --
>> 2.11.0
>>
>>
> 
> Noticed that min_timeout of the watchdog device is set to 1 but this
> function calls start with timeout set to 0. Even though this works I
> feel it is better to set min_timeout to 0.
> 

No. That would be wrong. If you want to be pedantic, write a new function
__jz4740_wdt_set_timeout(u16 clock_div, u16 timeout_value) and call it
instead, but don't mess with min_timeout.

Guenter