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

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Message-ID: <981498bb-70d8-4304-9b53-065576ae8dc7@kernel.org>
Date: Tue, 8 Apr 2025 11:39:40 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: 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 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.


Best regards,
Krzysztof