thermal: gov_step_wise: fix trip hysteresis to actually honour it

[lukaszsobala]

This makes hysteresis actually do something. Affects 28 mainline-style boards. Split from #532, narrower changes.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 579d0939-6a8c-455b-b1a9-eb53286adbbc

📥 Commits

Reviewing files that changed from the base of the PR and between c615710 and 9d81102.

📒 Files selected for processing (2)

• drivers/thermal/gov_step_wise.c
• include/linux/thermal.h

Included review availability: Your plan provides up to 2 included reviews per hour; 0 remain after this review.

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Walkthrough

The thermal zone device now stores a trips_engaged bitmap. The step-wise thermal governor reads optional trip hysteresis and keeps a trip engaged until the temperature falls below its hysteresis band. Without hysteresis, the governor retains the previous disengagement behavior.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 9d811

The change is narrowly scoped to thermal step-wise hysteresis behavior, and no actionable merge-blocking risk remains beyond normal checks and review.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the fix to trip hysteresis handling in the step-wise thermal governor.
Description check	✅ Passed	The description directly explains that the change makes hysteresis effective and identifies its scope.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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