linux-kernel - Re: [PATCH v11 1/5] dt-bindings: Introduce QCOM Sleep stats bindings

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Date:   Fri, 8 Oct 2021 14:20:24 +0530
From:   Maulik Shah <mkshah@...eaurora.org>
To:     Stephan Gerhold <stephan@...hold.net>
Cc:     swboyd@...omium.org, mka@...omium.org, evgreen@...omium.org,
        bjorn.andersson@...aro.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,
        lsrao@...eaurora.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v11 1/5] dt-bindings: Introduce QCOM Sleep stats bindings

Hi Stephan,

On 10/8/2021 1:20 AM, Stephan Gerhold wrote:
> On Thu, Oct 07, 2021 at 03:27:25PM +0530, Maulik Shah wrote:
>> From: Mahesh Sivasubramanian <msivasub@...eaurora.org>
>>
>> Add device binding documentation for Qualcomm Technologies, Inc. (QTI)
>> Sleep stats driver. The driver is used for displaying 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>
>> Reviewed-by: Stephen Boyd <swboyd@...omium.org>
>> ---
>>   .../bindings/soc/qcom/qcom-sleep-stats.yaml        | 47 ++++++++++++++++++++++
>>   1 file changed, 47 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/soc/qcom/qcom-sleep-stats.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/soc/qcom/qcom-sleep-stats.yaml b/Documentation/devicetree/bindings/soc/qcom/qcom-sleep-stats.yaml
>> new file mode 100644
>> index 0000000..5213daf
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/soc/qcom/qcom-sleep-stats.yaml
>> @@ -0,0 +1,47 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/soc/qcom/qcom-sleep-stats.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Qualcomm Technologies, Inc. (QTI) Sleep stats bindings
>> +
>> +maintainers:
>> +  - Maulik Shah <mkshah@...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
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> +  # Example of rpmh sleep stats
>> +  - |
>> +    sram@...0000 {
>> +      compatible = "qcom,rpmh-sleep-stats";
>> +      reg = <0x0c3f0000 0x400>;
>> +    };
>> +  # Example of rpm sleep stats
>> +  - |
>> +    sram@...0000 {
>> +      compatible = "qcom,rpm-sleep-stats";
>> +      reg = <0x04690000 0x400>;
>> +    };
> 
> Does this region really only contain "rpm-*sleep*-stats"? AFAICT this is
> really a more generic memory region where various offsets are read from.

Right the area contains all kind of sleep stats/logs.

> 
> These are all the offsets in msm8998-pm.dtsi downstream [1]:
>    ...9000c: rpm-rail-stats offset
>    ...90014: rpm-sleep-stats offset (RPM_DYNAMIC_ADDR in your driver)
>    ...90018: rpm-log offset
>    ...9001c: "RPM FREE HEAP SPACE"
> 
> How would you set up any of the other drivers if the entire region
> is declared as "rpm-sleep-stats"?

We don't need to setup other drivers.
The idea is to have single stats driver (qcom_sleep_stats) that can be 
enahanced to to read other stats also on both RPM/ PRMH targets.

Today this driver reads only sleep stats from offset 0x90014.
if in future say, we want to read rpm-rail-stats from offset 0x9000c 
then it can be added in the existing driver.

In the rpm data, add one more entry to indicate reading rpm-rail-stats,
something like below and add new compatible flag for the target, may be
"qcom,rpm-sleep-stats-legacy" and should work like,

#define RPM_RAIL_STATS_ADDR 0xc

static const struct stats_config rpm_data = {
         .stats_offset = 0,
         .num_records = 2,
         .appended_stats_avail = true,
         .dynamic_offset = true,
         .rpm_rail_stats = true,
};

and check in driver probe like

         if (config->rpm_rail_stats) {
	//create rpm rail stats related files.
         }

Similarly for other rpm-logs / any other stats can be added in same driver.

Hope this clarifies.

> 
> Perhaps this region should have a more generic name that represents what
> it actually is and not only one of the information it contains, similar
> to "qcom,rpm-msg-ram"?

sram looks good to me. Actually on RPM targets its RPM data ram and RPMH 
targets its msgram. To keep the name common sram is used here.

Thanks,
Maulik

> 
> Thanks,
> Stephan
> 
> [1]: https://source.codeaurora.org/quic/la/kernel/msm-4.4/tree/arch/arm/boot/dts/qcom/msm8998-pm.dtsi?h=LA.UM.8.4.1.c25#n271
> 

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