linux-kernel - Re: [PATCH v2 3/4] dt-bindings: watchdog: da9062: add watchdog timeout mode

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Date:   Tue, 30 Nov 2021 08:40:17 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
        Andrej Picej <andrej.picej@...ik.com>
Cc:     Support Opensource <Support.Opensource@...semi.com>,
        "wim@...ux-watchdog.org" <wim@...ux-watchdog.org>,
        "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "linux-imx@....com" <linux-imx@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 3/4] dt-bindings: watchdog: da9062: add watchdog
 timeout mode

On 11/30/21 8:11 AM, Adam Thomson wrote:
> On Guenter Roeck wrote:
> 
>>> Document the watchdog timeout mode property. If this property is used
>>> the user can select what happens on watchdog timeout. Set this property
>>> to 1 to enable SHUTDOWN (the device resets), set it to 0 and the device
>>> will go to POWERDOWN on watchdog timeout.
>>>
>>> Signed-off-by: Andrej Picej <andrej.picej@...ik.com>
>>> ---
>>>    Documentation/devicetree/bindings/watchdog/da9062-wdt.txt | 3 +++
>>>    1 file changed, 3 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/watchdog/da9062-wdt.txt
>> b/Documentation/devicetree/bindings/watchdog/da9062-wdt.txt
>>> index 950e4fba8dbc..e3e6e56cee21 100644
>>> --- a/Documentation/devicetree/bindings/watchdog/da9062-wdt.txt
>>> +++ b/Documentation/devicetree/bindings/watchdog/da9062-wdt.txt
>>> @@ -10,6 +10,9 @@ Optional properties:
>>>    - dlg,use-sw-pm: Add this property to disable the watchdog during suspend.
>>>    	Only use this option if you can't use the watchdog automatic suspend
>>>    	function during a suspend (see register CONTROL_B).
>>> +- dlg,wdt-sd: Set what happens on watchdog timeout. If this bit is set the
>>> +	watchdog timeout triggers SHUTDOWN, if cleared the watchdog triggers
>>> +	POWERDOWN. Can be 0 or 1.
>>>
>>
>> Why does it need a value ? Why not just bool ?
> 
> One argument might be that if the property isn't provided then the OTP
> configured value can persist without needing a FW change around this DT binding.
> 
> My belief though is that the majority of users would have this property set to 0
> by default in OTP, so a boolean would be OK I think here to enable watchdog
> shutdown.
> 

Sorry, you lost me.
	dlg,wdt-sd = <0>;
is the current situation, and identical to not having the property in
the first place.
	dlg,wdt-sd = <1>;
is new. I don't see the difference to
	dlg,wdt-sd;
vs. not having the property at all (which is, again, the current situation).
Since it has to be backward compatible,
	dlg,wdt-sd = <0>;
will always be identical to not having the property at all.
I can not find a situation where an integer would have any benefits over a boolean.

Guenter