sun60iw2: fix RTC on Orange Pi Zero 3W (use SoC RTC, drop phantom hym8563)

[periqles]

Description

Every Zero 3W boot currently starts in 1970 with rtc-hym8563 15-0051: could not init device, -22. Root cause: the board DTS enables an external hym8563 RTC that is not
populated on this board (schematic has no external RTC — only the SoC VCC-RTC domain),
while the SoC's own RTC (rtc-v201 @0x7090000, driver already built in) is explicitly
disabled with a /*Disable soc rtc*/ comment — likely inherited from a reference design.

Consequences of the wrong clock until NTP syncs: apt refuses repos ("Release file not
valid yet"), wrong early-boot timestamps, and no timekeeping at all for offline use.

Fix

• Enable the SoC RTC node, disable the phantom hym8563 (DTS patch 0009).
• Point RTC_HCTOSYS_DEVICE and RTC_SYSTOHC_DEVICE at rtc0, so the kernel restores the
  system clock from the RTC at boot and writes NTP-corrected time back to it every ~11 min.
  (With the phantom gone the SoC RTC registers as rtc0; rtc0 is also the kernel default and
  remains correct for family boards where a real external RTC registers first. Note this
  config is family-wide for sun60iw2 — reasoned through the 4 Pro / Cubie A7Z cases.)

Testing (Orange Pi Zero 3W hardware)

• /dev/rtc0 registers as sunxi-rtc 7090000.rtc; probe error gone
• Time set via RTC_SET_TIME is held and correctly advanced across reboots
• systemd-timesyncd keeps the RTC updated after NTP sync (11-min kernel sync)

Follow-up candidate (not this PR): the same phantom node pattern may exist on other
sun60iw2 family DTs.

Summary by CodeRabbit

• Bug Fixes
  • Improved system timekeeping by using the board’s built-in RTC for reading and saving system time.
  • Disabled the unavailable external RTC configuration to prevent incorrect or phantom clock detection.
  • Enabled reliable RTC support on Orange Pi Zero 3W devices.

[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between ee00ac7 and 741efdb.

📒 Files selected for processing (2)

• config/kernel/linux-sun60iw2-vendor.config
• patch/kernel/archive/sun60iw2-opi-vendor/0009-orangepizero3w-use-soc-rtc-drop-phantom-hym8563.patch

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📝 Walkthrough

Walkthrough

The Orange Pi Zero 3W device tree now enables the SoC RTC and disables the phantom external RTC. Kernel RTC settings now use rtc0 for system time synchronization.

Changes

RTC source selection

Layer / File(s)	Summary
Enable SoC RTC and disable phantom RTC patch/kernel/archive/sun60iw2-opi-vendor/0009-orangepizero3w-use-soc-rtc-drop-phantom-hym8563.patch	The device tree enables the SoC RTC and disables the external hym8563 RTC node.
Select rtc0 for system time config/kernel/linux-sun60iw2-vendor.config	Kernel boot-time clock reading and system-time-to-hardware-clock synchronization now use rtc0.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 741ef

This localized change enables the SoC RTC, disables the unpopulated external RTC, and directs system time synchronization to rtc0. No actionable merge-blocking risk remains beyond normal checks and review.

Suggested reviewers: shkolnik

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
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.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: fixing the Orange Pi Zero 3W RTC by using the SoC RTC and disabling the phantom hym8563 device.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (2 skipped: 2 unsupported.)

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[periqles]

the Orange Pi 4 Pro DTS has the identical pattern (&rtc disabled + hym8563 node on s_twi2). If the 4 Pro doesn't populate the external RTC either (no hardware to test it), it has the same 1970-boot bug and the same two-line fix applies. Worth a check by a 4 Pro owner; happy to extend this PR or follow up if confirmed.

[github-actions]

✅ This PR has been reviewed and approved — all set for merge!