M4-POWER-02 integrated physical qualification

Source 83d475ef71a3dd84f6e3cc483a7637b13520e4f7 builds one integrated production hardware candidate. Exact build receipt and hashes. M4 remains ACTIVE/PARTIAL. No new hardware pass is implied by compilation.

Latest result, 2026-09-15: [fresh authenticated inspection and full image-length readback](../hardware-evidence/2026-09-15-m5-entry/README.md) match this BOOTIMG. PC charging subsequently stops at 4.200073 V with latched voltage fault 0x8 and remains off after the reading falls. This is separate from the earlier OVP failure. SPM entries/resumes remain zero on the inspected boot; M4 is not ready to close or serve as a qualified M5 entry. No new deployment is requested.

Subsequent owner result, 2026-09-14: wall charging showed animation without recovery, requiring stock recharge. After Linux reinstall, read-only SSH evidence confirms POWER-02 starts 450-mA charging from a recognized PC source, then stops after about one second with latched OVP fault 0x10. Charging qualification has failed; the exact detector and earlier wall-session cause remain unresolved. The sequence below is the original candidate handoff, not a successful result or a new request to repeat flashing. The prior 70-mA gain baseline also failed.

2026-09-15 runtime workaround: two physical USB reconnects now pass with the MUSB child's runtime-PM policy held at on. The matching change is installed in /etc/init.d/S20y2-usb and scoped to POWER-02; it does not require flashing. This is a workaround, not a kernel fix. Added idle consumption is unmeasured. The short DCP wall test had no fault, but the prior charging failure and full M4 acceptance remain unresolved. A bounded persistent recorder now preserves diagnostics when a restart is necessary.

Deploy only BOOTIMG

Package: /home/luca/Dokumente/Code/Y2Linux/out/y2linux-m4-power-02/. Use its MT6582_BOOTIMG_only_scatter.txt in the established SP Flash Tool. Select Download Only, BOOTIMG only, and the package's BOOTIMG.img. Keep PRELOADER, LK/UBOOT, all partition tables, recovery, root/data and NVRAM unchecked. Never select Format or Firmware Upgrade. The user's authorization covers this integrated M4 pass; no bootloader modification is needed.

After a successful flash, disconnect USB and leave the Y2 off. Connect a normal wall charger without pressing Power. Record the actual screen text and whether the screen blanks automatically. Expected: a charging activity display for eight seconds, then darkness; a brief Power press shows status again. A fresh two-second Power hold and release requests normal boot only once voltage has been at least 3.4 V for three samples. Do not hold for the hardware emergency reset interval. Charging may continue offline indefinitely through normal termination/hold/recharge, without automatically starting Buildroot.

At low battery, remain in offline charging. No SSH/ECM is expected there. Minute-spaced kernel records preserve voltage, source, programmed limit, watchdog service, PMIC temperature, raw BATON/ISENSE and charge state for later retrieval after deliberate normal boot. No development process controls charging.

The prior kernel is preserved at fallback/BOOTIMG-previous.img. It restores M4-CHARGE-01 and its known limitations, including inhibition below 3.4 V. It must not be represented as an empty-battery recovery path.

One coherent physical session

The agent uses tools/development/qualify-m4-power.sh for explicit normal-API inventory, root/data sentinels, bounded OPP testing, audio, suspend and power phases. Both host shell and the actual production ARM BusyBox syntax check pass. It is a qualification helper, never a charger/watchdog or production PM owner.

1. Demonstrate wall-source offline entry, timed blanking and brief status input.

   Then perform deliberate normal Power-on with the source still connected. Retrieve boot metadata and the retained offline charge history. Establish sustained gain before heavy load or repeated power-transition tests.

2. Test PC and power-bank source classification/charging, including off-state

   insertion without normal userspace. Check the PC offline ACM-only descriptor and absence of ECM/SSH. Wall/bank charging must not require enumeration.

3. In normal userspace retain boot ID, RTC, root/data sentinels, complete power,

   thermal, clock, regulator and device inventory. Use normal interfaces only. Check fresh thermal acquisition against actual response before any load test.

4. Qualify each 598/747.5/1040-MHz OPP repeatedly at the retained 1.15 V, bounded

   load and cooling constraints; verify WFI usage. Do not call fixed-voltage frequency scaling voltage DVFS.

5. Verify charger-active suspend inhibition while screen-off charging continues.

   After charging is safely inhibited or disconnected, test s2idle fallback, then SPM deep suspend with Power and RTC wake. Require an unchanged boot ID, actual cpu_resume counter advancement and no PCM debug fault. Record real duration and voltage behavior; no calibrated standby current is available.

6. After resume test display/backlight, Power, volume, navigation/wheel, optional

   external SD, root/data sentinels, ALSA/CS43131 and the proven 44.1-kHz playback. No mounted-filesystem fsck, raw storage changes or emergency reset cycles. Wider M3 48-kHz/channel/repeat tests and #27 remain separate unless blocking.

7. Set RTC through its standard API using the recorded host UTC time, preserving

   any unrelated alarm and all RTC spare/boot words. Check reboot persistence, suspend alarm, deep wake, and hardware-off persistence where supported.

8. Qualify ordinary reboot and actual BBPU hardware poweroff with the cable

   removed, subsequent ordinary Power boot, then poweroff while connected returning to offline charging. Offline unplug must turn off; reinsertion must return offline. A black screen alone is not proof of power removal.

9. Retain the final-current termination and recharge evidence, including the

   unattended-by-userspace offline path. Low-voltage source entry must show actual recovery; crossing 3.4 V must never automatically boot the full OS.

Every physical result goes into the current M4 acceptance matrix. Unrun, failed or unobservable cases remain open. Neither simulated charger completion nor a host suspend-sequence test closes a hardware gate. M5 is not started during this session.