| Message ID | 3c2dd41b585efe44d361f41fcea0181ff2a9c9c5.1702571292.git.robin.murphy@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | perf/arm_cspmu: Add devicetree support | expand |
On Thu, 14 Dec 2023 16:31:07 +0000, Robin Murphy wrote: > Add a binding for implementations of the Arm CoreSight Performance > Monitoring Unit Architecture. Not to be confused with CoreSight debug > and trace, the PMU architecture defines a standard MMIO interface for > event counters following a similar design to the CPU PMU architecture, > where the implementation and most of its features are discoverable > through ID registers. > > CC: Rob Herring <robh+dt@kernel.org> > CC: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org> > CC: Conor Dooley <conor+dt@kernel.org> > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > --- > v2: Use reg-io-width instead of a new property; tweak descriptions > --- > .../bindings/perf/arm,coresight-pmu.yaml | 39 +++++++++++++++++++ > 1 file changed, 39 insertions(+) > create mode 100644 Documentation/devicetree/bindings/perf/arm,coresight-pmu.yaml > My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check' on your patch (DT_CHECKER_FLAGS is new in v5.13): yamllint warnings/errors: ./Documentation/devicetree/bindings/perf/arm,coresight-pmu.yaml:27:111: [warning] line too long (114 > 110 characters) (line-length) dtschema/dtc warnings/errors: doc reference errors (make refcheckdocs): See https://patchwork.ozlabs.org/project/devicetree-bindings/patch/3c2dd41b585efe44d361f41fcea0181ff2a9c9c5.1702571292.git.robin.murphy@arm.com The base for the series is generally the latest rc1. A different dependency should be noted in *this* patch. If you already ran 'make dt_binding_check' and didn't see the above error(s), then make sure 'yamllint' is installed and dt-schema is up to date: pip3 install dtschema --upgrade Please check and re-submit after running the above command yourself. Note that DT_SCHEMA_FILES can be set to your schema file to speed up checking your schema. However, it must be unset to test all examples with your schema.
On Thu, 14 Dec 2023 16:31:07 +0000, Robin Murphy wrote: > Add a binding for implementations of the Arm CoreSight Performance > Monitoring Unit Architecture. Not to be confused with CoreSight debug > and trace, the PMU architecture defines a standard MMIO interface for > event counters following a similar design to the CPU PMU architecture, > where the implementation and most of its features are discoverable > through ID registers. > > CC: Rob Herring <robh+dt@kernel.org> > CC: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org> > CC: Conor Dooley <conor+dt@kernel.org> > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > --- > v2: Use reg-io-width instead of a new property; tweak descriptions > --- > .../bindings/perf/arm,coresight-pmu.yaml | 39 +++++++++++++++++++ > 1 file changed, 39 insertions(+) > create mode 100644 Documentation/devicetree/bindings/perf/arm,coresight-pmu.yaml > With the line wrapping fixed: Reviewed-by: Rob Herring <robh@kernel.org>
On 14/12/2023 17:31, Robin Murphy wrote: > + > + reg: > + items: > + - description: Register page 0 > + - description: Register page 1, if the PMU implements the dual-page extension > + minItems: 1 > + > + interrupts: > + items: > + - description: Overflow interrupt > + > + cpus: > + description: If the PMU is associated with a particular CPU or subset of CPUs, array of phandles to those CPUs > + > + reg-io-width: > + description: Granularity at which PMU register accesses are single-copy atomic > + default: 4 > + enum: [4, 8] > + > + If there is going to be new posting: just one blank line > +required: > + - compatible > + - reg > + > +additionalProperties: false Why no example to validate the binding? Best regards, Krzysztof
On 15/12/2023 9:44 am, Krzysztof Kozlowski wrote: > On 14/12/2023 17:31, Robin Murphy wrote: >> + >> + reg: >> + items: >> + - description: Register page 0 >> + - description: Register page 1, if the PMU implements the dual-page extension >> + minItems: 1 >> + >> + interrupts: >> + items: >> + - description: Overflow interrupt >> + >> + cpus: >> + description: If the PMU is associated with a particular CPU or subset of CPUs, array of phandles to those CPUs >> + >> + reg-io-width: >> + description: Granularity at which PMU register accesses are single-copy atomic >> + default: 4 >> + enum: [4, 8] >> + >> + > > If there is going to be new posting: just one blank line Ack, I've fixed that up locally along with the linewrap (since Will's already winding down for holidays, I'm assuming I'll resend this for 6.9 in the new year now). >> +required: >> + - compatible >> + - reg >> + >> +additionalProperties: false > > Why no example to validate the binding? IMO for such a trivial binding built out of common properties, an equally trivial example isn't going to add any value, since it won't do anything more than re-state the individual property definitions above. In bindings where we have conditional relationships between properties, or complex encodings where a practical example can help explain a definition (e.g. a map/mask pair for a set of input values), then absolutely, an example can add something more to help the author and/or users. But otherwise, the thing I've really grown to like about schema is how thoroughly self-describing the definitions themselves can now be. Thanks, Robin.
On 15/12/2023 19:39, Robin Murphy wrote: >>> +required: >>> + - compatible >>> + - reg >>> + >>> +additionalProperties: false >> >> Why no example to validate the binding? > > IMO for such a trivial binding built out of common properties, an > equally trivial example isn't going to add any value, since it won't do > anything more than re-state the individual property definitions above. > In bindings where we have conditional relationships between properties, > or complex encodings where a practical example can help explain a > definition (e.g. a map/mask pair for a set of input values), then > absolutely, an example can add something more to help the author and/or > users. But otherwise, the thing I've really grown to like about schema > is how thoroughly self-describing the definitions themselves can now be. The example is used to validate the schema. Best regards, Krzysztof
On 2023-12-18 7:03 am, Krzysztof Kozlowski wrote: > On 15/12/2023 19:39, Robin Murphy wrote: >>>> +required: >>>> + - compatible >>>> + - reg >>>> + >>>> +additionalProperties: false >>> >>> Why no example to validate the binding? >> >> IMO for such a trivial binding built out of common properties, an >> equally trivial example isn't going to add any value, since it won't do >> anything more than re-state the individual property definitions above. >> In bindings where we have conditional relationships between properties, >> or complex encodings where a practical example can help explain a >> definition (e.g. a map/mask pair for a set of input values), then >> absolutely, an example can add something more to help the author and/or >> users. But otherwise, the thing I've really grown to like about schema >> is how thoroughly self-describing the definitions themselves can now be. > > The example is used to validate the schema. Can you clarify what that *means*, though? As far as I can tell from a bit of experimentation, "make dt_bindings_check" picks up errors in the schema definition itself just the same whether an example is present or not. Thus I still fail to understand what else would be validated by me writing an example here, other than my personal ability to comprehend my own binding. Yes, I'm well aware that back when we were bootstrapping dtschema it was useful to confirm that schemas were written to correctly describe *existing* known-good DT fragments. However with new bindings like this we've already reached the end goal, where we write an authoritative schema first, then the users follow from there. As I alluded to above, there are reasons why I would actually prefer *not* to provide a usage example here - frankly if a user doesn't understand which parts of the architecture their hardware implements, and/or can't figure out how to copy a single compatible string and write a standard reg property, I would much rather they come to me asking how to write a DT entry, than blindly copy-paste a verbatim example into their DTS, then come to me reporting a "bug" with the driver crashing or failing to probe. I'd love to say I have no experience to base that judgement on, but... Thanks, Robin.
On 19/12/2023 15:24, Robin Murphy wrote: > On 2023-12-18 7:03 am, Krzysztof Kozlowski wrote: >> On 15/12/2023 19:39, Robin Murphy wrote: >>>>> +required: >>>>> + - compatible >>>>> + - reg >>>>> + >>>>> +additionalProperties: false >>>> >>>> Why no example to validate the binding? >>> >>> IMO for such a trivial binding built out of common properties, an >>> equally trivial example isn't going to add any value, since it won't do >>> anything more than re-state the individual property definitions above. >>> In bindings where we have conditional relationships between properties, >>> or complex encodings where a practical example can help explain a >>> definition (e.g. a map/mask pair for a set of input values), then >>> absolutely, an example can add something more to help the author and/or >>> users. But otherwise, the thing I've really grown to like about schema >>> is how thoroughly self-describing the definitions themselves can now be. >> >> The example is used to validate the schema. > > Can you clarify what that *means*, though? As far as I can tell from a > bit of experimentation, "make dt_bindings_check" picks up errors in the > schema definition itself just the same whether an example is present or > not. Thus I still fail to understand what else would be validated by me > writing an example here, other than my personal ability to comprehend my > own binding. You miss here the part that the actual binding is used to verify the example used. This is something entirely different than validating schema against meta-schema. > > Yes, I'm well aware that back when we were bootstrapping dtschema it was > useful to confirm that schemas were written to correctly describe > *existing* known-good DT fragments. However with new bindings like this > we've already reached the end goal, where we write an authoritative > schema first, then the users follow from there. As I alluded to above, > there are reasons why I would actually prefer *not* to provide a usage > example here - frankly if a user doesn't understand which parts of the > architecture their hardware implements, and/or can't figure out how to > copy a single compatible string and write a standard reg property, I > would much rather they come to me asking how to write a DT entry, than > blindly copy-paste a verbatim example into their DTS, then come to me > reporting a "bug" with the driver crashing or failing to probe. I'd love > to say I have no experience to base that judgement on, but... Sure, considering the size of the binding the benefits of the example here are rather low. Best regards, Krzysztof
On 2023-12-20 7:30 am, Krzysztof Kozlowski wrote: > On 19/12/2023 15:24, Robin Murphy wrote: >> On 2023-12-18 7:03 am, Krzysztof Kozlowski wrote: >>> On 15/12/2023 19:39, Robin Murphy wrote: >>>>>> +required: >>>>>> + - compatible >>>>>> + - reg >>>>>> + >>>>>> +additionalProperties: false >>>>> >>>>> Why no example to validate the binding? >>>> >>>> IMO for such a trivial binding built out of common properties, an >>>> equally trivial example isn't going to add any value, since it won't do >>>> anything more than re-state the individual property definitions above. >>>> In bindings where we have conditional relationships between properties, >>>> or complex encodings where a practical example can help explain a >>>> definition (e.g. a map/mask pair for a set of input values), then >>>> absolutely, an example can add something more to help the author and/or >>>> users. But otherwise, the thing I've really grown to like about schema >>>> is how thoroughly self-describing the definitions themselves can now be. >>> >>> The example is used to validate the schema. >> >> Can you clarify what that *means*, though? As far as I can tell from a >> bit of experimentation, "make dt_bindings_check" picks up errors in the >> schema definition itself just the same whether an example is present or >> not. Thus I still fail to understand what else would be validated by me >> writing an example here, other than my personal ability to comprehend my >> own binding. > > You miss here the part that the actual binding is used to verify the > example used. This is something entirely different than validating > schema against meta-schema. If I say "All cats are orange.", it's certainly meta-valid in terms of being a well-constructed English sentence, but is it true? If I then show you a picture of Garfield as an example to prove my assertion, does that make it any more true? As long as a definition is self-consistent to begin with, contriving a "correct" example *from* it does not and can not prove anything about the overall correctness of that definition. However, I guess that the subtlety of that initial condition might be where your argument comes from - I've been taking it for granted here since I'm sufficiently confident that I can write correct schema which means what I intend it to mean, but as a reviewer I appreciate that you're not necessarily going to make the same assumption, so there's value for you if patches include a sanity check to give the bot a chance to weed out stuff that's completely broken. I would still hesitate to call that "validation", though. Thanks, Robin. >> >> Yes, I'm well aware that back when we were bootstrapping dtschema it was >> useful to confirm that schemas were written to correctly describe >> *existing* known-good DT fragments. However with new bindings like this >> we've already reached the end goal, where we write an authoritative >> schema first, then the users follow from there. As I alluded to above, >> there are reasons why I would actually prefer *not* to provide a usage >> example here - frankly if a user doesn't understand which parts of the >> architecture their hardware implements, and/or can't figure out how to >> copy a single compatible string and write a standard reg property, I >> would much rather they come to me asking how to write a DT entry, than >> blindly copy-paste a verbatim example into their DTS, then come to me >> reporting a "bug" with the driver crashing or failing to probe. I'd love >> to say I have no experience to base that judgement on, but... > > Sure, considering the size of the binding the benefits of the example > here are rather low. > > Best regards, > Krzysztof >
diff --git a/Documentation/devicetree/bindings/perf/arm,coresight-pmu.yaml b/Documentation/devicetree/bindings/perf/arm,coresight-pmu.yaml new file mode 100644 index 000000000000..0fcc5bb610f3 --- /dev/null +++ b/Documentation/devicetree/bindings/perf/arm,coresight-pmu.yaml @@ -0,0 +1,39 @@ +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/perf/arm,coresight-pmu.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Arm Coresight Performance Monitoring Unit Architecture + +maintainers: + - Robin Murphy <robin.murphy@arm.com> + +properties: + compatible: + const: arm,coresight-pmu + + reg: + items: + - description: Register page 0 + - description: Register page 1, if the PMU implements the dual-page extension + minItems: 1 + + interrupts: + items: + - description: Overflow interrupt + + cpus: + description: If the PMU is associated with a particular CPU or subset of CPUs, array of phandles to those CPUs + + reg-io-width: + description: Granularity at which PMU register accesses are single-copy atomic + default: 4 + enum: [4, 8] + + +required: + - compatible + - reg + +additionalProperties: false
Add a binding for implementations of the Arm CoreSight Performance Monitoring Unit Architecture. Not to be confused with CoreSight debug and trace, the PMU architecture defines a standard MMIO interface for event counters following a similar design to the CPU PMU architecture, where the implementation and most of its features are discoverable through ID registers. CC: Rob Herring <robh+dt@kernel.org> CC: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org> CC: Conor Dooley <conor+dt@kernel.org> Signed-off-by: Robin Murphy <robin.murphy@arm.com> --- v2: Use reg-io-width instead of a new property; tweak descriptions --- .../bindings/perf/arm,coresight-pmu.yaml | 39 +++++++++++++++++++ 1 file changed, 39 insertions(+) create mode 100644 Documentation/devicetree/bindings/perf/arm,coresight-pmu.yaml