linux-kernel - Re: [PATCH 1/2] dt-bindings: watchdog: airoha: document watchdog for Airoha EN7581

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Message-ID: <85e5e88b-524f-4e57-a5cf-6e7eed65839d@roeck-us.net>
Date: Thu, 19 Sep 2024 06:23:24 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Christian Marangi <ansuelsmth@...il.com>,
 Krzysztof Kozlowski <krzk@...nel.org>
Cc: Wim Van Sebroeck <wim@...ux-watchdog.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, linux-watchdog@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 Lorenzo Bianconi <lorenzo@...nel.org>, upstream@...oha.com
Subject: Re: [PATCH 1/2] dt-bindings: watchdog: airoha: document watchdog for
 Airoha EN7581

On 9/19/24 05:39, Christian Marangi wrote:
> On Thu, Sep 19, 2024 at 02:35:02PM +0200, Krzysztof Kozlowski wrote:
>> On 19/09/2024 14:26, Christian Marangi wrote:
>>> Document watchdog for Airoha EN7581. This SoC implement a simple
>>> watchdog that supports a max timeout of 28 seconds.
>>>
>>> The watchdog ticks on half the BUS clock and require the BUS frequency
>>> to be provided.
>>
>> Clock provider should implement clk_get_rate()...
>>
> 
> The BUS clock is internal and not exposed to the system hence
> clk_get_rate is not possible saddly.
> 
>>>
>>
>> ...
>>
>>> +maintainers:
>>> +  - Christian Marangi <ansuelsmth@...il.com>
>>> +
>>> +allOf:
>>> +  - $ref: watchdog.yaml#
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: airoha,en7581-wdt
>>> +
>>> +  reg:
>>> +    maxItems: 1
>>> +
>>> +  clock-frequency:
>>> +    description: BUS frequency in Hz (timer ticks at half the BUS freq)
>>> +    const: 300000000
>>
>> Which bus frequency? Aren't you missing here clock input?
> 
> I'm putting here property to describe the internal clock to what the
> watchdog is attached. Should I drop this and just hardcode it
> internally to the driver or maybe declare the clock to be 150000000
> directly?
> 
> Tick frequency is already not well defined so I tought it was a good
> idea to describe it in DT.
> 

If the value is a constant it should not be in devicetree.

Guenter