linux-kernel - Re: [PATCH V6 3/4] dt-bindings: interconnect: Add generic compatible qcom,epss-l3-perf

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Message-ID: <zchtx32wtii2mzy2pp4lp4gdaim7w56kih7jcqes4tyhu24r3n@dagazlsdgdcv>
Date: Wed, 27 Nov 2024 18:53:02 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Rob Herring <robh@...nel.org>
Cc: Raviteja Laggyshetty <quic_rlaggysh@...cinc.com>, 
	Georgi Djakov <djakov@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, Odelu Kukatla <quic_okukatla@...cinc.com>, 
	Mike Tipton <quic_mdtipton@...cinc.com>, Sibi Sankar <quic_sibis@...cinc.com>, 
	linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6 3/4] dt-bindings: interconnect: Add generic compatible
 qcom,epss-l3-perf

On Wed, Nov 27, 2024 at 08:23:04AM -0600, Rob Herring wrote:
> On Mon, Nov 25, 2024 at 05:45:10PM +0000, Raviteja Laggyshetty wrote:
> > EPSS instance on sc7280, sm8250 SoCs, use PERF_STATE register instead of
> > REG_L3_VOTE to scale L3 clocks, hence adding a new generic compatible
> > "qcom,epss-l3-perf" for these targets.
> 
> Is this a h/w difference from prior blocks or you just want to use B 
> instead of A while the h/w has both A and B? The latter sounds like 
> driver policy.
> 
> It is also an ABI break for s/w that didn't understand 
> qcom,epss-l3-perf.

As the bindings keep old compatible strings in addition to the new
qcom,epss-l3-perf, where is the ABI break? Old SW will use old entries,
newer can use either of those.

> 
> > 
> > Signed-off-by: Raviteja Laggyshetty <quic_rlaggysh@...cinc.com>
> > ---
> >  .../devicetree/bindings/interconnect/qcom,osm-l3.yaml      | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/interconnect/qcom,osm-l3.yaml b/Documentation/devicetree/bindings/interconnect/qcom,osm-l3.yaml
> > index 21dae0b92819..e24399ca110f 100644
> > --- a/Documentation/devicetree/bindings/interconnect/qcom,osm-l3.yaml
> > +++ b/Documentation/devicetree/bindings/interconnect/qcom,osm-l3.yaml
> > @@ -28,12 +28,15 @@ properties:
> >            - const: qcom,osm-l3
> >        - items:
> >            - enum:
> > -              - qcom,sc7280-epss-l3
> >                - qcom,sc8280xp-epss-l3
> >                - qcom,sm6375-cpucp-l3
> > -              - qcom,sm8250-epss-l3
> >                - qcom,sm8350-epss-l3
> >            - const: qcom,epss-l3
> > +      - items:
> > +          - enum:
> > +              - qcom,sc7280-epss-l3
> > +              - qcom,sm8250-epss-l3
> > +          - const: qcom,epss-l3-perf
> >  
> >    reg:
> >      maxItems: 1
> > -- 
> > 2.39.2
> > 

-- 
With best wishes
Dmitry