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

[Krzysztof Kozlowski]

On 27/11/2024 17:53, Dmitry Baryshkov wrote:
> 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.
No, this change drops qcom,epss-l3 and adds new fallback. How old
software can work in such case? It's broken.

Best regards,
Krzysztof