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

[Conor Dooley <conor@kernel.org>]

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On Thu, Jun 27, 2024 at 06:08:15AM +0000, Manikandan.M@microchip.com wrote:
> Hi Conor,
> 
> On 26/06/24 2:29 pm, Conor Dooley wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > 
> > ForwardedMessage.eml
> > 
> > Subject:
> > Re: [PATCH v2 4/5] dt-bindings: gpio: convert Atmel GPIO to json-schema
> > From:
> > Conor Dooley <conor@kernel.org>
> > Date:
> > 26/06/24, 2:29 pm
> > 
> > To:
> > Manikandan.M@microchip.com
> > CC:
> > linus.walleij@linaro.org, brgl@bgdev.pl, robh@kernel.org, 
> > krzk+dt@kernel.org, conor+dt@kernel.org, Nicolas.Ferre@microchip.com, 
> > alexandre.belloni@bootlin.com, claudiu.beznea@tuxon.dev, arnd@arndb.de, 
> > Durai.ManickamKR@microchip.com, linux-gpio@vger.kernel.org, 
> > devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, 
> > linux-kernel@vger.kernel.org
> > 
> > 
> > On Wed, Jun 26, 2024 at 08:32:41AM +0000,Manikandan.M@microchip.com  wrote:
> >> On 25/06/24 10:04 pm, Conor Dooley wrote:
> >>> Re: [PATCH v2 4/5] dt-bindings: gpio: convert Atmel GPIO to json-schema
> >>> From: Conor Dooley<conor@kernel.org>
> >>> On Tue, Jun 25, 2024 at 10:05:24AM +0530, Manikandan Muralidharan wrote:
> >>>> Convert the Atmel GPIO controller binding document to DT schema format
> >>>> using json-schema.
> >>>> The compatible string "microchip,sam9x7-gpio" is added as well.
> >>>>
> >>>> Signed-off-by: Manikandan Muralidharan<manikandan.m@microchip.com>
> >>>> ---
> >>>> changes in v2:
> >>>> - Fix bot errors with 'make dt_binding_check', missed to add
> >>>> "atmel,at91rm9200-gpio" as separate compatible for devices that uses it
> >>>> - Remove label from example
> >>>> - Add default entry for #gpio-lines property
> >>>> - Add new compatible string details in commit message
> >>>> ---
> >>>>    .../bindings/gpio/atmel,at91rm9200-gpio.yaml  | 81 +++++++++++++++++++
> >>>>    .../devicetree/bindings/gpio/gpio_atmel.txt   | 31 -------
> >>>>    2 files changed, 81 insertions(+), 31 deletions(-)
> >>>>    create mode 100644 Documentation/devicetree/bindings/gpio/atmel,at91rm9200-gpio.yaml
> >>>>    delete mode 100644 Documentation/devicetree/bindings/gpio/gpio_atmel.txt
> >>>>
> >>>> diff --git a/Documentation/devicetree/bindings/gpio/atmel,at91rm9200-gpio.yaml b/Documentation/devicetree/bindings/gpio/atmel,at91rm9200-gpio.yaml
> >>>> new file mode 100644
> >>>> index 000000000000..3dd70933ed8e
> >>>> --- /dev/null
> >>>> +++ b/Documentation/devicetree/bindings/gpio/atmel,at91rm9200-gpio.yaml
> >>>> @@ -0,0 +1,81 @@
> >>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >>>> +%YAML 1.2
> >>>> +---
> >>>> +$id:http://devicetree.org/schemas/gpio/atmel,at91rm9200-gpio.yaml#
> >>>> +$schema:http://devicetree.org/meta-schemas/core.yaml#
> >>>> +
> >>>> +title: Microchip GPIO controller (PIO)
> >>>> +
> >>>> +maintainers:
> >>>> +  - Manikandan Muralidharan<manikandan.m@microchip.com>
> >>>> +
> >>>> +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.

Thanks,
Conor.

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