| Message ID | 1686138469-1464-1-git-send-email-quic_rohiagar@quicinc.com |
|---|---|
| Headers | show |
| Series | Add devicetree support for SDX75 Modem and IDP | expand |
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@quicinc.com> > Acked-by: Viresh Kumar <viresh.kumar@linaro.org> > --- > 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. I ask this because, we don't add these compatible strings in the driver [1] which means there is not SoC specific handling and there is no module load assist (module alias matching by user space based on device presence). Thanks, Pavan
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@quicinc.com> >> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> >> --- >> 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") Konrad > > I ask this because, we don't add these compatible strings in the driver > [1] which means there is not SoC specific handling and there is no > module load assist (module alias matching by user space based on device > presence). > > Thanks, > Pavan
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@quicinc.com> > >> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> > >> --- > >> 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