On Thu, Jun 27, 2024 at 04:42:24PM +0100, Conor Dooley wrote:

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+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.

quoted

- 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@microchip.com>

Thanks,
Conor.