linux-kernel - Re: [PATCH v2 4/5] dt-bindings: gpio: convert Atmel GPIO to json-schema

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Date: Thu, 27 Jun 2024 16:44:54 +0100
From: Conor Dooley <conor@...nel.org>
To: Manikandan.M@...rochip.com
Cc: linus.walleij@...aro.org, brgl@...ev.pl, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org,
	Nicolas.Ferre@...rochip.com, alexandre.belloni@...tlin.com,
	claudiu.beznea@...on.dev, arnd@...db.de,
	Durai.ManickamKR@...rochip.com, linux-gpio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/5] dt-bindings: gpio: convert Atmel GPIO to
 json-schema

On Thu, Jun 27, 2024 at 04:42:24PM +0100, Conor Dooley wrote:
> > >>>> +properties:
> > >>>> +  compatible:
> > >>>> +    oneOf:
> > >>>> +      - items:
> > >>>> +          - enum:
> > >>>> +              - atmel,at91sam9x5-gpio
> > >>>> +              - microchip,sam9x60-gpio
> > >>>> +          - const: atmel,at91rm9200-gpio
> > >>>> +      - items:
> > >>>> +          - enum:
> > >>>> +              - microchip,sam9x7-gpio
> > >>>> +          - const: microchip,sam9x60-gpio
> > >>>> +          - const: atmel,at91rm9200-gpio
> > >>> It's worth pointing out that this is required, because the driver
> > >>> implements a different set of ops for the sam9x60. There's not just more
> > >>> of them, they're different too.
> > >>> Are the sam9x60 and at91rm9200 are actually compatible, or is the
> > >>> fallback here some mistake that originated in the dts?
> > >>>
> > >> The PIO3 pinctrl driver uses the compatible "atmel,at91rm9200-gpio" to
> > >> find the number of active GPIO banks and also to differentiate them from
> > >> the pinmux child nodes.The driver probe fails if the at91rm9200 is not
> > >> present in the GPIO bank compatible property list.
> > >> For sam9x7, "microchip,sam9x60-gpio" is used as the fallback compatible
> > >> and "atmel,at91rm9200-gpio" is added by default to avoid probe issues
> > >> and help find the number of GPIO banks by the driver.
> > > That's unfortunately not what I asked. Forget about
> > > at91_pinctrl_child_count() for a minute and answer the question again:
> > > Are the sam9x60 and at91rm9200 actually compatible?
> > > 
> > > Hints:
> > > - Do the registers that are in the at91rm9200 have the same behaviour in
> > >    the sam9x60?
> > The registers in at91rm9200 have the same behavior as sam9x60 expect 
> > that the former supports only 2 Peripheral function per pin while 
> > sam9x60 supports 4.
> > > - Are the new registers in sam9x60 optional, so that if all sam9x60 code
> > >    was deleted from the driver, the driver would still work for the subset
> > >    of features that the at91rm9200 already supports?
> > at91rm9200 function will work for sam9x60 but not up-to its full 
> > potential.The new registers in sam9x60 for drive-strength, slew-rate, 
> > debounce, pull-down will help drive the the current pinmux configs for 
> > sam9x60/9x7 board DT.
> 
> Right. The compatible setup makes sense then, just an explanation for
> why should go into your commit message.

Gah, I forgot to say, with that:
Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>

Thanks,
Conor.

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