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

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Message-ID: <66f3cf7b.050a0220.3af9f1.2fe0@mx.google.com>
Date: Wed, 25 Sep 2024 10:53:11 +0200
From: Christian Marangi <ansuelsmth@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Wim Van Sebroeck <wim@...ux-watchdog.org>,
	Guenter Roeck <linux@...ck-us.net>, 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 Thu, Sep 19, 2024 at 02:42:33PM +0200, Krzysztof Kozlowski wrote:
> On 19/09/2024 14:39, 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?
> 
> If this stays, then please mention "internal watchdog bus frequency".
> 
> If this is internal and it is part of an SoC (so not board!) why would
> we need it in DT? I would imagine this is fixed per SoC, thus deduced
> from the compatible.
> 
> clock-frequency property is legacy and in general discouraged. This
> might be an exception, but for that I would like to see more of
> explanations.
>

Ok it took a while but finally I got my answer. The Documentation had a
mistake and conflicting info. (one bus was said running at 250Mhz instead
of 300Mhz) With this error fixed I can correctly attach a clock and drop
this stupiud thing. Win-Win for everyone!

> > 
> > Tick frequency is already not well defined so I tought it was a good
> > idea to describe it in DT.
> > 
> 

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