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PM: Introduce docs for s2idle #562

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@DhruvaG2000 DhruvaG2000 commented Dec 8, 2025

Document all about s2idle and PSCI and how the whole stack helps us in selecting between low power modes on the TI AM62L

@DhruvaG2000 DhruvaG2000 changed the title feat(linux): Add s2idle docs [WIP][DNM] Add s2idle docs Dec 8, 2025
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github-actions bot commented Dec 8, 2025

New warnings found with rstcheck:

source/linux/Foundational_Components/Power_Management/pm_psci_s2idle.rst:25: (ERROR/3) Unexpected indentation.

cshilwant
cshilwant reviewed Dec 8, 2025
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source/linux/Foundational_Components/Power_Management/pm_psci_s2idle.rst Outdated
Suspend-to-Idle (s2idle), also known as "freeze," is a generic, pure software, light-weight variant of system suspend.
In this state, the Linux kernel freezes user space tasks, suspends devices, and then puts all CPUs into their deepest available idle state.

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The section identifier line should be of equal length to the section name.

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DhruvaG2000 commented Dec 9, 2025

@cshilwant , and rest I'll mark the PR ready for review once it has undergone LPM team internal review. Till then requesting you to hold off reviews.
This is going to be a major documentation update for AM62L PM story hence might take some time to get reviews and complete.

Thanks!

kwillis01
kwillis01 suggested changes Dec 9, 2025
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New warnings found with rstcheck:

source/linux/Foundational_Components/Power_Management/pm_psci_s2idle.rst:48: (WARNING/2) Bullet list ends without a blank line; unexpected unindent.
source/linux/Foundational_Components/Power_Management/pm_psci_s2idle.rst:29: (ERROR/3) Error parsing content block for the "list-table" directive: two-level bullet list expected, but row 4 does not contain a second-level bullet list.

@DhruvaG2000 DhruvaG2000 force-pushed the s2idle_doc branch 2 times, most recently from c7f9288 to 4a0b798 Compare December 23, 2025 13:14
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New warnings found with rstcheck:

source/linux/Foundational_Components/Power_Management/pm_psci_s2idle.rst:302: (WARNING/2) Bullet list ends without a blank line; unexpected unindent.
source/linux/Foundational_Components/Power_Management/pm_psci_s2idle.rst:283: (ERROR/3) Error parsing content block for the "list-table" directive: two-level bullet list expected, but row 4 does not contain a second-level bullet list.

kwillis01
kwillis01 suggested changes Dec 29, 2025
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Besides the execution level things, everything else looks good to me! Good work on adding all of this, it's very infomative

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feat(linux): Add s2idle docs
09ca039 
Introduce the concept of s2idle and how we use it for mode
selection

Signed-off-by: Dhruva Gole <[email protected]>
@DhruvaG2000 DhruvaG2000 changed the title [WIP][DNM] Add s2idle docs PM: Introduce docs for s2idle Dec 30, 2025
@DhruvaG2000 DhruvaG2000 marked this pull request as ready for review January 2, 2026 04:34
ti-scaria
ti-scaria reviewed Jan 2, 2026
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source/linux/Foundational_Components/Power_Management/pm_psci_s2idle.rst
Why OSI?
========

OSI mode allows the OS to make better power decisions because it has visibility into:
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The below 3 points are coming on a single line as seen in the preview. It would be better if they are in separate lines as bullets

source/linux/Foundational_Components/Power_Management/pm_psci_s2idle.rst
| v
| CPU enters low-power
| hardware state
|
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should there be something in the flow as to indicate why / on what kind of event the system is resuming

source/linux/Foundational_Components/Power_Management/pm_psci_s2idle.rst
``idle-state`` nodes using the ``arm,psci-suspend-param`` property. This mechanism,
leveraging ``cpuidle`` and ``s2idle``, allows the kernel to abstract complex platform-specific
low-power modes into a generic framework. The ``idle-state`` nodes in the Device Tree define these power states,
including their entry/exit latencies and target power consumption, enabling the ``cpuidle`` governor to make informed
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should it be mentioned that in the case of s2idle, the governor picks the deepest possible idle state

source/linux/Foundational_Components/Power_Management/pm_psci_s2idle.rst
* - **Latency**
- Lower
- High, primarily due to the overhead of **CPU Hotplug** for non-boot CPUs

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since s2idle will allow the mode selection using QoS paramter, should the details regarding that be mentioned here

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