Re: [PATCH v2 1/7] dt-bindings: pwm: Document Tegra194 and Tegra264 controllers

[Krzysztof Kozlowski <krzk@kernel.org>]

On Wed, Mar 25, 2026 at 03:22:13PM +0100, Thierry Reding wrote:
> On Wed, Mar 25, 2026 at 07:16:59PM +0900, Mikko Perttunen wrote:
> > From: Thierry Reding <treding@nvidia.com>
> > 
> > The PWM controller found on Tegra264 is largely compatible with the one
> > on prior generations, but it comes with some extra features, hence a new
> > compatible string is needed.
> > 
> > Signed-off-by: Thierry Reding <treding@nvidia.com>
> > Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
> > ---
> >  Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.yaml | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.yaml b/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.yaml
> > index 41cea4979132..15706d2a808d 100644
> > --- a/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.yaml
> > +++ b/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.yaml
> > @@ -16,6 +16,8 @@ properties:
> >        - enum:
> >            - nvidia,tegra20-pwm
> >            - nvidia,tegra186-pwm
> > +          - nvidia,tegra194-pwm
> > +          - nvidia,tegra264-pwm
> 
> I think this was lost during the earlier conversation we had on the
> split of these patches. Krzysztof had pointed out that tegra194-pwm is
> now a duplicate entry. I don't know exactly how it ended up like this,
> but I'm pretty sure what I meant was:
> 
> 	- items:
> 	    - const: tegra264-pwm
> 	    - const: tegra194-pwm
> 
> This mirrors the fact that this is in fact backwards-compatible with
> Tegra194 but also has additional features that we need the Tegra264
> compatible string for.

If the devices are compatible. You have quite a lot of differences in
the driver, so the question is whether driver will work fine when bound
via old interface.

This was EXACTLY explained in DTS101 last year. I really focused on that
because after repeating for few years and two previous speeches people
still claim compatibility is something else. :(

Best regards,
Krzysztof