On Fri, Jun 09, 2023 at 11:17:08AM +0200, Konrad Dybcio wrote: > > > On 9.06.2023 07:00, Pavan Kondeti wrote: > > On Wed, Jun 07, 2023 at 05:17:48PM +0530, Rohit Agarwal wrote: > >> Add compatible for EPSS CPUFREQ-HW on SDX75. > >> > >> Signed-off-by: Rohit Agarwal <quic_rohiagar@xxxxxxxxxxx> > >> Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx> > >> --- > >> Documentation/devicetree/bindings/cpufreq/cpufreq-qcom-hw.yaml | 1 + > >> 1 file changed, 1 insertion(+) > >> > >> diff --git a/Documentation/devicetree/bindings/cpufreq/cpufreq-qcom-hw.yaml b/Documentation/devicetree/bindings/cpufreq/cpufreq-qcom-hw.yaml > >> index a6b3bb8..866ed2d 100644 > >> --- a/Documentation/devicetree/bindings/cpufreq/cpufreq-qcom-hw.yaml > >> +++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-qcom-hw.yaml > >> @@ -36,6 +36,7 @@ properties: > >> - qcom,sa8775p-cpufreq-epss > >> - qcom,sc7280-cpufreq-epss > >> - qcom,sc8280xp-cpufreq-epss > >> + - qcom,sdx75-cpufreq-epss > >> - qcom,sm6375-cpufreq-epss > >> - qcom,sm8250-cpufreq-epss > >> - qcom,sm8350-cpufreq-epss > > > > This is a very basic question, not completely related to this patch. > > Apologies in advance. > > > > What is the rationale for adding a new soc string under compatible and > > using it in the new soc device tree? Is it meant for documentation purpose? > > i.e one know what all SoCs / boards supported by this device node. > It's two-fold: > > 1. The device tree describes the hardware, and for lack of better terms (e.g. > an SoC-specific version number of the block that is identical to all other > implementations of that revision on all SoCs that use it), we tend to > associate it with the SoC it's been (first) found on. > > 2. In case we ever needed to introduce a SoC-specific quirk, we can just add > an of_is_compatible-sorta check to the driver and not have to update the > device trees. This is very important for keeping backwards compatibility, > as it's assumed that not everybody may be running the latest one. This > means we have to avoid ABI breaks (unless we have *very* good reasons, like > "this would have never worked anyway" or "it was not described properly > and worked on this occasion by pure luck") > Thanks Konrad for the explanation. The #2 is a clear winner here. It makes complete sense. In devices like USB, we have PID/VID through which quirks can be implemented later. So I guess the same analogy applies here. Like you said in (1), the devices are identified with SoC compatible string. Thanks, Pavan
