linux-kernel - Re: [PATCH v6 1/4] dt-bindings: Introduce SoC sleep stats bindings

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Date:   Fri, 12 Mar 2021 11:14:09 -0600
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Maulik Shah <mkshah@...eaurora.org>, evgreen@...omium.org,
        mka@...omium.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, agross@...nel.org,
        dianders@...omium.org, linux@...ck-us.net, rnayak@...eaurora.org,
        ilina@...eaurora.org, lsrao@...eaurora.org,
        Mahesh Sivasubramanian <msivasub@...eaurora.org>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v6 1/4] dt-bindings: Introduce SoC sleep stats bindings

On Mon 08 Feb 18:23 CST 2021, Stephen Boyd wrote:

> Quoting Maulik Shah (2021-02-04 06:21:45)
> > +
> > +description:
> > +  Always On Processor/Resource Power Manager maintains statistics of the SoC
> > +  sleep modes involving powering down of the rails and oscillator clock.
> > +
> > +  Statistics includes SoC sleep mode type, number of times low power mode were
> > +  entered, time of last entry, time of last exit and accumulated sleep duration.
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - qcom,rpmh-sleep-stats
> > +      - qcom,rpm-sleep-stats
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +
> > +examples:
> > +  # Example of rpmh sleep stats
> > +  - |
> > +    rpmh-sleep-stats@...0000 {
> > +      compatible = "qcom,rpmh-sleep-stats";
> > +      reg = <0 0x0c3f0000 0 0x400>;
> > +    };
> 
> Maybe it should just be another reg property of the rpmh or rpm node?
> Then the rpmh driver can create the stats "device" at driver probe time,
> or just roll it into the same thing. It looks pretty weird to have a
> device in DT for this given that it's not really hardware, more like a
> place that the processor writes some stuff about what's going on in the
> SoC related to power management. 
> 

Given that there is some hardware (although just a chunk of sram) and
that the same driver is used for RPM, which we don't represent on the
mmio bus I think the proposed design makes sense.

Regards,
Bjorn

> > +  # Example of rpm sleep stats
> > +  - |
> > +    rpm-sleep-stats@...0000 {
> > +      compatible = "qcom,rpm-sleep-stats";
> > +      reg = <0 0x04690000 0 0x400>;
> > +    };
> > +...