[Bug 221776] HP OmniBook X Flip - Broken UCSI firmware / Slow charging

https://bugzilla.kernel.org/show_bug.cgi?id=221776

--- Comment #3 from David Del Sol ([email protected]) ---
Updating this report with the verified root cause, found since the original
filing.

The slow-charging issue is NOT UCSI firmware corruption. Root cause: the EC
only enables normal charging when the OS claims _OSI("Windows 2022"). Verified:
- DSDT/SSDT (via strings on /sys/firmware/acpi/tables/*) contain OSI checks
only up to "Windows 2022"; the kernel's default claimed OSI strings stop before
that.
- Adding acpi_osi=! acpi_osi="Windows 2022" to the kernel cmdline restores
31-33 W charging immediately, reproducibly, on kernels 7.1.6 and 6.18.42-LTS,
across multiple charge cycles (currently 27.8 W, battery 79%).
- This works with ucsi_acpi loaded -- the driver does not need to be
blacklisted, so the proposed ucsi_acpi.c DMI quirk in Comment 1 is unnecessary
and is withdrawn.

Per Greg's note: the correct upstream fix is a DMI-scoped OSI quirk in
drivers/acpi/osi.c (linux-acpi mailing list). Filed as a new report with full
evidence and EC RAM attachments:
  https://bugzilla.kernel.org/show_bug.cgi?id=221866

Separate, intermittent issue (still open, tracked in 221866): on ~1 in 4
plug/unplug events the 65 W charger's PD contract occasionally sticks at 5 V /
3 A (~0.2 W to battery) until reboot. UCSI driver reload and suspend/resume did
not recover it. Not reproduced in later cycles; appears to be a PD
renegotiation race.

Closing this bug as resolved-by-workaround: acpi_osi=! acpi_osi="Windows 2022"
on the kernel command line.

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