linux-kernel - Re: [PATCH v3 1/2] dt-bindings: watchdog: Add NXP Software Watchdog Timer

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Message-ID: <0ac343fe-e835-1c0d-55e7-5963cc24fc45@oss.nxp.com>
Date: Tue, 8 Apr 2025 13:30:18 +0300
From: Ghennadi Procopciuc <ghennadi.procopciuc@....nxp.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>, wim@...ux-watchdog.org
Cc: linux@...ck-us.net, linux-watchdog@...r.kernel.org,
 linux-kernel@...r.kernel.org, S32@....com, ghennadi.procopciuc@....com,
 thomas.fossati@...aro.org, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 1/2] dt-bindings: watchdog: Add NXP Software Watchdog
 Timer

On 4/8/2025 12:39 PM, Krzysztof Kozlowski wrote:
> On 08/04/2025 11:03, Daniel Lezcano wrote:
>> On 08/04/2025 10:21, Krzysztof Kozlowski wrote:
>>> On 07/04/2025 18:03, Daniel Lezcano wrote:
>>>> +
>>>> +allOf:
>>>> +  - $ref: watchdog.yaml#
>>>> +
>>>> +properties:
>>>> +  compatible:
>>>> +    oneOf:
>>>> +      - const: nxp,s32g2-swt
>>>> +      - items:
>>>> +          - const: nxp,s32g3-swt
>>>> +          - const: nxp,s32g2-swt
>>>> +
>>>> +  reg:
>>>> +    maxItems: 1
>>>> +
>>>> +  clocks:
>>>> +    items:
>>>> +      - description: Counter clock
>>>> +      - description: Module clock
>>>> +      - description: Register clock
>>>> +    minItems: 1
>>>
>>> Why clocks are flexible? The SoC does not change between boards. It
>>> should be a fixed list - block receives that number of clocks or does
>>> not... unless you meant that different instances of the block have
>>> different clocks?
>>
>> The documentation describe the watchdog module with a clock for the 
>> counter, a clock for the register and the last one for the module.
>>
>> IIUC, these clocks are enabled when the system is powered-on or exits 
>> suspend.
>>
>> The driver does not have a control on them.
>>
>> The only usage of the clock is to retrieve the rate of the counter in 
>> order to compute the maximum timeout. So only one is needed.
>>
>> However Ghennadi would like to describe the register and the module 
>> clocks in case there is SoC variant where it is possible to have control 
>> on them [1]
> 
> Different SoC means different compatible, so I don't get why this is
> relevant here. Either these clocks inputs are there in the hardware or not.
> 
>>
>> The goal is to give the description the flexibility to describe just one 
>> because the other ones are not needed for this s32g2/3 platform.
> 
> But bindings are not meant to be flexible but accurately describe the
> hardware. If hardware always has these clock inputs, then they are
> supposed to be always provided.
> 

Indeed, as mentioned in my previous replies, the SWT hardware module has
three clocks as inputs: counter, module, and register.

> 
> Best regards,
> Krzysztof
> 
> 

-- 
Regards,
Ghennadi