linux-kernel - Re: [PATCH v4 1/4] dt-bindings: Introduce SoC sleep stats bindings

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Message-ID: <158378046147.66766.9861199454487445583@swboyd.mtv.corp.google.com>
Date:   Mon, 09 Mar 2020 12:01:01 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Maulik Shah <mkshah@...eaurora.org>, evgreen@...omium.org,
        mka@...omium.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, agross@...nel.org,
        dianders@...omium.org, rnayak@...eaurora.org, ilina@...eaurora.org,
        lsrao@...eaurora.org,
        Mahesh Sivasubramanian <msivasub@...eaurora.org>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v4 1/4] dt-bindings: Introduce SoC sleep stats bindings

Quoting Bjorn Andersson (2020-03-09 11:51:20)
> On Mon 09 Mar 11:23 PDT 2020, Stephen Boyd wrote:
> 
> > Quoting Maulik Shah (2020-03-09 04:14:14)
> > > From: Mahesh Sivasubramanian <msivasub@...eaurora.org>
> > > 
> > > Add device binding documentation for Qualcomm Technologies, Inc. (QTI)
> > > SoC sleep stats driver. The driver is used for displaying SoC sleep
> > > statistic maintained by Always On Processor or Resource Power Manager.
> > > 
> > > Cc: devicetree@...r.kernel.org
> > > Signed-off-by: Mahesh Sivasubramanian <msivasub@...eaurora.org>
> > > Signed-off-by: Lina Iyer <ilina@...eaurora.org>
> > > Signed-off-by: Maulik Shah <mkshah@...eaurora.org>
> > > Reviewed-by: Rob Herring <robh@...nel.org>
> > > Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > > ---
> > >  .../bindings/soc/qcom/soc-sleep-stats.yaml         | 46 ++++++++++++++++++++++
> > >  1 file changed, 46 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/soc/qcom/soc-sleep-stats.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/soc/qcom/soc-sleep-stats.yaml b/Documentation/devicetree/bindings/soc/qcom/soc-sleep-stats.yaml
> > > new file mode 100644
> > > index 00000000..7c29c61
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/soc/qcom/soc-sleep-stats.yaml
> > > @@ -0,0 +1,46 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/soc/qcom/soc-sleep-stats.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Qualcomm Technologies, Inc. (QTI) SoC sleep stats bindings
> > > +
> > > +maintainers:
> > > +  - Maulik Shah <mkshah@...eaurora.org>
> > > +  - Lina Iyer <ilina@...eaurora.org>
> > > +
> > > +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 0xc3f0000 0 0x400>;
> > > +    };
> > > +  # Example of rpm sleep stats
> > > +  - |
> > > +    rpm_sleep_stats@...0000 {
> > 
> > Node names don't have underscores. It really feels like we should be able
> > to get away with not having this device node at all. Why can't we have
> > the rpm message ram be a node that covers the entire range and then have
> > that either create a platform device for debugfs stats or just have it
> > register the stat information from whatever driver attaches to that
> > node?
> > 
> > Carving this up into multiple nodes and making compatible strings
> > doesn't seem very useful here because we're essentially making device
> > nodes in DT for logical software components that exist in the rpm
> > message ram.
> 
> It's been a while since I discussed this with Lina, but iirc I opted for
> the model you suggest and we concluded that it wouldn't fit with the RPM
> case.
> 
> And given that, for reasons unknown to me, msgram isn't a single region,
> but a set of adjacent memory regions, this does seem to represent
> hardware better.
> 

I guess there's message ram and code ram or something like that? Maybe
that's the problem? Either way it sounds like the node name needs to be
fixed to have dashes and then this is fine to keep. Describing memory
like this in DT just makes me sad.