[Bug 221142] New: ucsi_acpi actively breaks USB-C PD charging on Lenovo Legion Pro 7 (Arrow Lake)

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=221142

            Bug ID: 221142
           Summary: ucsi_acpi actively breaks USB-C PD charging on Lenovo
                    Legion Pro 7 (Arrow Lake)
           Product: Drivers
           Version: 2.5
          Hardware: Intel
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: USB
          Assignee: drivers_usb@kernel-bugs.kernel.org
          Reporter: alex@alstergee.com
        Regression: No

The ucsi_acpi driver actively interferes with USB-C Power Delivery negotiation
on the Lenovo Legion Pro 7 16IAX10H (83F5, Intel Arrow Lake, BIOS Q7CN44WW).
Blacklisting ucsi_acpi completely fixes the issue — the EC's PD controller
negotiates correctly on its own.

SYSTEM:
- Lenovo Legion Pro 7 16IAX10H (product ID 83F5)
- Intel Core Ultra 9 275HX (Arrow Lake)
- BIOS Q7CN44WW (Nov 2025, latest available)
- Kernel 6.18.0

SYMPTOMS WITH ucsi_acpi LOADED:
- USB-C PD chargers connect briefly then drop after 1-3 minutes
- voltage_now always reads 0 in /sys/class/power_supply/ucsi-source-psy-*/
- usb_power_delivery_revision on partner reports 0.0 (should be 3.0)
- No source-capabilities PDO objects ever appear in sysfs
- GET_PDOS appears to return empty data from the EC
- GET_CONNECTOR_STATUS returns incomplete RDO
- Some chargers never establish a PD contract at all (Shargeek 100W: only 1.4W)
- Failed PD negotiations wedge the UCSI PPM — requires full reboot to recover
- ACPI workqueue warnings: "acpi_os_execute_deferred hogged CPU for >10000us"

RESULTS WITH ucsi_acpi BLACKLISTED:
- Shargeek 100W: 1.4W → 40-55W (full PD negotiation at proper voltage)
- Anker 65W: 5W → expected full power
- Barrel jack 330W: unaffected (70W, bypasses USB-C)

The EC's PD controller handles negotiation correctly without OS involvement.
The ucsi_acpi driver queries the broken UCSI mailbox and interferes with what
would otherwise be a working PD contract.

This is the same class of Lenovo EC firmware bug as:
- ThinkPad T14 Gen 5: https://github.com/fwupd/firmware-lenovo/issues/521
  (Lenovo internal ticket LO-4169 — EC returns static/dummy RDO)
- Framework Laptop 16: PDOs read as 0x00000000 despite successful PD
negotiation

RELATED KERNEL PATCHES:
- Benson Leung, Dec 2025: Fix voltage_now/current_now for non-PD sources
  https://lkml.org/lkml/2025/12/8/912
- Benson Leung, Dec 2025: Fix voltage/current max for non-Fixed PDOs
  https://lkml.org/lkml/2025/12/8/913 (commit 6811e0a08bdc)
  (These fix reporting but don't address the EC returning empty PDO data)

PROPOSED FIX:
The kernel could add a quirk for Lenovo platforms where the UCSI PPM is known
to return broken PDO data, either:
1. Skip GET_PDOS calls on affected platforms (let EC handle PD autonomously)
2. Add a module parameter to make ucsi_acpi passive/read-only
3. Detect empty GET_PDOS responses and back off instead of interfering

WORKAROUND:
echo "blacklist ucsi_acpi" > /etc/modprobe.d/blacklist-ucsi.conf

STEPS TO REPRODUCE:
1. Boot Lenovo Legion Pro 7 16IAX10H with kernel 6.18
2. Plug in any USB-C PD charger
3. Observe charging starts briefly then drops (BAT0/status → Discharging)
4. Check /sys/class/power_supply/ucsi-source-psy-*/voltage_now → always 0
5. Blacklist ucsi_acpi, reboot, plug charger → charges at full PD power

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