> -----Messaggio originale----- > Da: Sudeep Holla <sudeep.holla@xxxxxxx> > Inviato: lunedì 10 agosto 2020 14:45 > A: ansuelsmth@xxxxxxxxx > Cc: 'Viresh Kumar' <viresh.kumar@xxxxxxxxxx>; 'Rafael J. Wysocki' > <rjw@xxxxxxxxxxxxx>; 'Rob Herring' <robh+dt@xxxxxxxxxx>; linux- > pm@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx > Oggetto: Re: R: [RFC PATCH v2 2/2] dt-bindings: cpufreq: Document Krait > CPU Cache scaling > > On Mon, Aug 10, 2020 at 01:15:24PM +0200, ansuelsmth@xxxxxxxxx > wrote: > > > > > > > -----Messaggio originale----- > > > Da: Sudeep Holla <sudeep.holla@xxxxxxx> > > > Inviato: lunedì 10 agosto 2020 10:02 > > > A: Ansuel Smith <ansuelsmth@xxxxxxxxx> > > > Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx>; Rafael J. Wysocki > > > <rjw@xxxxxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; linux- > > > pm@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux- > > > kernel@xxxxxxxxxxxxxxx > > > Oggetto: Re: [RFC PATCH v2 2/2] dt-bindings: cpufreq: Document Krait > CPU > > > Cache scaling > > > > > > On Sat, Aug 08, 2020 at 01:49:12AM +0200, Ansuel Smith wrote: > > > > Document dedicated Krait CPU Cache Scaling driver. > > > > > > > > Signed-off-by: Ansuel Smith <ansuelsmth@xxxxxxxxx> > > > > --- > > > > .../bindings/cpufreq/krait-cache-scale.yaml | 92 > > > +++++++++++++++++++ > > > > 1 file changed, 92 insertions(+) > > > > create mode 100644 > Documentation/devicetree/bindings/cpufreq/krait- > > > cache-scale.yaml > > > > > > > > diff --git a/Documentation/devicetree/bindings/cpufreq/krait-cache- > > > scale.yaml b/Documentation/devicetree/bindings/cpufreq/krait-cache- > > > scale.yaml > > > > new file mode 100644 > > > > index 000000000000..f10b1f386a99 > > > > --- /dev/null > > > > +++ b/Documentation/devicetree/bindings/cpufreq/krait-cache- > > > scale.yaml > > > > @@ -0,0 +1,92 @@ > > > > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause > > > > +%YAML 1.2 > > > > +--- > > > > +$id: http://devicetree.org/schemas/cpufreq/krait-cache-scale.yaml# > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml# > > > > + > > > > +title: Krait Cpu Cache Frequency Scaling dedicated driver > > > > + > > > > +maintainers: > > > > + - Ansuel Smith <ansuelsmth@xxxxxxxxx> > > > > + > > > > +description: | > > > > + This Scale the Krait CPU Cache Frequency and optionally voltage > > > > + when the Cpu Frequency is changed (using the cpufreq notifier). > > > > + > > > > + Cache is scaled with the max frequency across all core and the cache > > > > + frequency will scale based on the configured threshold in the dts. > > > > + > > > > + The cache is hardcoded to 3 frequency bin, idle, nominal and high. > > > > + > > > > +properties: > > > > + compatible: > > > > + const: qcom,krait-cache > > > > + > > > > > > How does this fit in the standard cache hierarchy nodes ? Extend the > > > example to cover that. > > > > > > > I think i didn't understand this question. You mean that I should put > > in the example how the standard l2 cache nodes are defined? > > > > I was referring to something like below which I found now in > arch/arm/boot/dts/qcom-msm8974.dtsi: > L2: l2-cache { > compatible = "cache"; > cache-level = <2>; > qcom,saw = <&saw_l2>; > }; > > > > > + clocks: > > > > + description: Phandle to the L2 CPU clock > > > > + > > > > + clock-names: > > > > + const: "l2" > > > > + > > > > + voltage-tolerance: > > > > + description: Same voltage tollerance of the Krait CPU > > > > + > > > > + l2-rates: > > > > + description: | > > > > + Frequency the L2 cache will be scaled at. > > > > + Value is in Hz. > > > > + $ref: /schemas/types.yaml#/definitions/uint32-array > > > > + items: > > > > + - description: idle > > > > + - description: nominal > > > > + - description: high > > > > + > > > > > > Why can't you re-use the standard OPP v2 bindings ? > > > > > > > Isn't overkill to use the OPP v2 bindings to represent the the microvolt > > related to the le freq? Is the OPP v1 sufficient? > > Should be fine if it is allowed. v2 came out in the flow of my thought > and was not intentional. > > > Also I can't find a way to reflect this specific case where the l2 rates > > are changed based on the cpu freq value? Any idea about that? > > > > OK, I am always opposed to giving such independent controls in the kernel > as one can play around say max cpu freq and lowest cache or vice-versa > and create instabilities. IMO this should be completely hidden from OS. > But I know these are old platforms, so I will shut my mouth ;) > If we really want to deny this practice, I can add a check in the probe function to fail if the l2 freq threshold is less than the cpu freq. > -- > Regards, > Sudeep
