Re: [PATCH 1/3] dt-binding: document QCOM platforms for CTCU device

[Suzuki K Poulose]

On 03/02/2026 09:36, Konrad Dybcio wrote:
> On 2/3/26 10:31 AM, Suzuki K Poulose wrote:
> > On 03/02/2026 09:00, Jie Gan wrote:
> > > On 2/3/2026 4:50 PM, Konrad Dybcio wrote:
> > > > On 2/3/26 9:08 AM, Jie Gan wrote:
> > > > > Document the platforms that fallback to using the qcom,sa8775p-ctcu
> > > > > compatible for probing.
> > > > >
> > > > > Signed-off-by: Jie Gan <jie.gan@xxxxxxxxxxxxxxxx>
> > > > > ---
> > > > >    Documentation/devicetree/bindings/arm/qcom,coresight-ctcu.yaml | 4 ++++
> > > > >    1 file changed, 4 insertions(+)
> > > > >
> > > > > diff --git a/Documentation/devicetree/bindings/arm/qcom,coresight- ctcu.yaml b/Documentation/devicetree/bindings/arm/qcom,coresight- ctcu.yaml
> > > > > index e002f87361ad..68853db52bef 100644
> > > > > --- a/Documentation/devicetree/bindings/arm/qcom,coresight-ctcu.yaml
> > > > > +++ b/Documentation/devicetree/bindings/arm/qcom,coresight-ctcu.yaml
> > > > > @@ -29,6 +29,10 @@ properties:
> > > > >        oneOf:
> > > > >          - items:
> > > > >              - enum:
> > > > > +              - qcom,glymur-ctcu
> > > > > +              - qcom,hamoa-ctcu
> > > > > +              - qcom,kaanapali-ctcu
> > > > > +              - qcom,pakala-ctcu
> > > >
> > > > Platforms with existing numeric compatibles should continue to use them,
> > > > so that the mess is somewhat containable
> > >
> > > Sure Konrad. So for Pakala, I will change it back to qcom,sm8750-ctcu
> >
> > Why do we need different compatibles for the others ? Are they not all compliant to the CTCU programming model ? i.e., sa8775p-ctcu ? or even,
> > a generic,
> >
> > qcom,coresight-ctcu
>
> It's a huge anti-pattern with the DT maintainers, since a compatible is
> the only way to effectively differentiate different implementations (i.e.
> instances on different SoCs) of an IP block

Do you mean, same IP block integrated to different SoC ? Or are they
different implementations altogether ? Why are these not applicable for
other components ? (e.g., Tnoc, I-Tnoc, TPDA, TPDM etc ?)

> This is important for the case where a DTB is shipped as part of firmware
> and can not be replaced - if some quirk needs to be applied retroactively,
> we can look for "qcom,glymur-ctcu" without affecting all the 50 other'
> users of the effectively-identical IP block

Fair enough, thank for the explanation.

Kind regards
Suzuki

> In this case, we're already reducing the impact on the driver, as that
> only looks for the single fallback compatible (qcom,sa8775p-ctcu)
>
> Konrad