Re: [PATCH] dt-bindings: timer: renesas,rz-mtu3: Use #pwm-cells = <3>

["u.kleine-koenig@baylibre.com" <u.kleine-koenig@baylibre.com>]

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Hello,

On Wed, Mar 25, 2026 at 01:24:40PM +0000, Cosmin-Gabriel Tanislav wrote:
> Sorry for replying to an old patch, but the context is relevant to my
> question.
> 
> I'm working on adding MTU3 support for a new platform, Renesas RZ/T2H.
> 
> From this patch, it is clear that new platforms should use
> #pwm-cells = <3>; as <2> is deprecated.
> 
> What I would like to clarify is whether existing platforms are also
> expected to be migrated from #pwm-cells = <2> to #pwm-cells = <3>.
> 
> My understanding is that changing the provider to #pwm-cells = <3> would
> break existing consumers that still specify only two cells in their PWM
> specifiers, since those references would then fail the checks inside
> of_phandle_iterator_next().

The conversion doesn't break dtbs, because in a single dtb consumer and
PWM device are consistent. So from my POV updating is fine.

> There are no existing consumers in-tree, but there might be out-of-tree
> ones that depend on #pwm-cells = <2>;.

That might happen for out-of-tree dts files that include the SoC's
.dtsi. IMHO it's ok to break these.

> If we're okay with the ABI breakage I can proceed with the changes for
> existing platforms too.

The reason that made me stop continuing the conversion myself is the
somewhat stuck discussion at
https://patchwork.ozlabs.org/project/linux-pwm/patch/crk42dsypmbyqk7avldghjq32vslmalfmmouwxzgtdci4agfhz@rkbmxj5z22fx/
.

Best regards
Uwe

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