[v4,0/4] Introduce SoC sleep stats driver

Changes in v4:
- Address bjorn's comments from v3 on change 2.
- Add bjorn's Reviewed-by on change 3 and 4.

Changes in v3:
- Address stephen's comments from v2 in change 1 and 2.
- Address bjorn's comments from v2 in change 3 and 4.
- Add Rob and bjorn's Reviewed-by on YAML change.

Changes in v2:
- Convert Documentation to YAML.
- Address stephen's comments from v1.
- Use debugfs instead of sysfs.
- Add sc7180 dts changes for sleep stats
- Add defconfig changes to enable driver
- Include subsystem stats from [1] in this single stats driver.
- Address stephen's comments from [1]
- Update cover letter inline to mention [1]

Qualcomm Technologies, Inc. (QTI)'s chipsets support SoC level low power
modes. SoCs Always On Processor/Resource Power Manager produces statistics
of the SoC sleep modes involving lowering or powering down of the rails and
the oscillator clock.

Additionally multiple subsystems present on SoC like modem, spss, adsp,
cdsp maintains their low power mode statistics in shared memory (SMEM).

Statistics includes SoC sleep mode type, number of times LPM entered, time
of last entry, exit, and accumulated sleep duration in seconds.

This series adds a driver to read the stats and export to debugfs.

[1] https://lore.kernel.org/patchwork/patch/1149381/

Mahesh Sivasubramanian (2):
  dt-bindings: Introduce soc sleep stats bindings for Qualcomm SoCs
  soc: qcom: Add SoC sleep stats driver

Maulik Shah (2):
  arm64: dts: qcom: sc7180: Enable soc sleep stats
  arm64: defconfig: Enable SoC sleep stats driver for Qualcomm

 .../bindings/soc/qcom/soc-sleep-stats.yaml         |  47 ++++
 arch/arm64/boot/dts/qcom/sc7180.dtsi               |   5 +
 arch/arm64/configs/defconfig                       |   1 +
 drivers/soc/qcom/Kconfig                           |  10 +
 drivers/soc/qcom/Makefile                          |   1 +
 drivers/soc/qcom/soc_sleep_stats.c                 | 279 +++++++++++++++++++++
 6 files changed, 343 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/soc/qcom/soc-sleep-stats.yaml
 create mode 100644 drivers/soc/qcom/soc_sleep_stats.c

Quoting Maulik Shah (2020-03-09 04:14:14)
> From: Mahesh Sivasubramanian <msivasub@codeaurora.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@vger.kernel.org
> Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>
> Signed-off-by: Lina Iyer <ilina@codeaurora.org>
> Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
> Reviewed-by: Rob Herring <robh@kernel.org>
> Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.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@codeaurora.org>
> +  - Lina Iyer <ilina@codeaurora.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@c3f0000 {
> +      compatible = "qcom,rpmh-sleep-stats";
> +      reg = <0 0xc3f0000 0 0x400>;
> +    };
> +  # Example of rpm sleep stats
> +  - |
> +    rpm_sleep_stats@4690000 {

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.