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

[Thierry Reding <thierry.reding@kernel.org>]

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On Thu, Mar 26, 2026 at 09:47:30AM +0900, Mikko Perttunen wrote:
> On 2026-03-25 15:22 +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
> 
> Ah, I see now.
> 
> > 
> > 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.
> 
> The Tegra264 PWM controller is in fact not backwards compatible with
> Tegra194. It is close but not quite. I will drop the duplicate tegra194
> compatible string and update the commit message accordingly.

Ah... I remembered this wrongly. Yes, since the enable bit was moved to
a different register, we cannot claim backwards-compatibility.

Thierry

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