linux-kernel - Re: [PATCH] dt-bindings: microchip: atmel,at91rm9200-tcb: remove mandatory interrupts property

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Message-ID: <YgZw/IB1V7NTRUJQ@robh.at.kernel.org>
Date:   Fri, 11 Feb 2022 08:21:48 -0600
From:   Rob Herring <robh@...nel.org>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Eugen.Hristev@...rochip.com, Nicolas.Ferre@...rochip.com,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, clement.leger@...tlin.com
Subject: Re: [PATCH] dt-bindings: microchip: atmel,at91rm9200-tcb: remove
 mandatory interrupts property

On Fri, Feb 04, 2022 at 11:36:02AM +0100, Alexandre Belloni wrote:
> On 04/02/2022 10:28:43+0000, Eugen.Hristev@...rochip.com wrote:
> > On 2/4/22 11:46 AM, Alexandre Belloni wrote:
> > > On 04/02/2022 10:14:46+0200, Eugen Hristev wrote:
> > >> The timer block can be used only to be read and to measure time in a polling
> > >> fashion. This can be used by Linux like this for example, or it can be used
> > >> by different projects which do not have interrupt controllers, or do not
> > >> wish to enable them (e.g. U-boot).
> > >> As DT is ABI, the binding should relate to all possible use cases and describe
> > >> the hardware and the requirements.
> > >> The interrupt is not a hard requirement for the timer to function in a
> > >> specific way.
> > >> Thus, choose to remove the interrupts property from the mandatory list of
> > >> properties.
> > >>
> > > 
> > > The correct hardware description is that the interrupt is present on the
> > > IP. Having software behave differently depending on the presence of that
> > > property is configuration, not hardware description.
> > 
> > I agree. The interrupt is present on the IP, thus the property exists 
> > and it's described.
> > However, the interrupt is not mandatory for IP operations. Thus it 
> > should not be in the list of mandatory properties.
> > 
> 
> If the interrupt is always present, it is mandatory, it doesn't matter
> whether is is used or necessary to get the IP to work.

Agreed.