Re: usb: typec: ucsi: DP alt mode fails on hotplug on Acer Swift SF314-57 (Ice Lake), "failed to register partner alt modes (-5)"

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

Hi,

Thanks for the report, and sorry to keep you waiting.

On Mon, Oct 05, 2026 at 01:22:07PM +0900, Mohammad Fadhil Rasyidin Parinduri wrote:
> Hi Heikki,
> 
> DisplayPort alternate mode does not come up when I hotplug a USB-C to
> DisplayPort cable into the USB-C port of an Acer Swift SF314-57. Each plug
> event logs "con1: failed to register partner alt modes (-5)", the cable
> enumerates as a USB Billboard device, and the DP connector stays
> disconnected. The monitor wakes and then goes back to standby.
> 
> If the cable is plugged in before power-on, the display works, which I take
> to mean the firmware enters DP mode during boot. After one unplug and
> replug, the display does not come back until the next reboot.
> 
> My setup:
> 
>    - Machine: Acer Swift SF314-57 (board Floris_IL)
>    - CPU: Intel Core i5-1035G1 (Ice Lake)
>    - BIOS/EC: Insyde V1.21, 2021-01-18 (newest version I can find for this
>    model)
>    - UCSI: ucsi_acpi, USBC000:00, Type-C revision 1.3, PD revision 3.0
>    - Kernels: 7.2.3-arch1-3 (stock Arch) and 7.2.5 (Arch-based downstream
>    build). Both behave the same.
>    - Cable: USB-C to DisplayPort cable with a Genesys Logic converter
>    (Billboard device 05e3:0f01). The same cable and monitor work on another
>    USB-C device.
>    - Monitor: Samsung LS27FG53x
> 
> To reproduce:
> 
>    1. Boot with the cable plugged in. The external display works.
>    2. Unplug the cable, wait about 10 seconds, plug it back in.
>    3. The display stays dark and the DP connector reports disconnected.
> 
> Reloading ucsi_acpi (modprobe -r ucsi_acpi && modprobe ucsi_acpi) and
> replugging does not help.
> 
> With ucsi_acpi and typec_ucsi both unloaded, a replug also fails: the
> Billboard device enumerates, no UCSI messages are logged, and DP-1 stays
> disconnected. So the firmware does not enter DP mode on its own after boot,
> even with the OS sending no UCSI commands.
> 
> After a failed hotplug, sysfs shows:
> 
> /sys/class/drm/card2-DP-1/status          disconnected
> /sys/class/typec/port0/port0.0/svid        8087  (active: yes)
> /sys/class/typec/port0-partner/number_of_alternate_modes   1
> /sys/class/typec/port0-partner/port0-partner.0/svid        ff01
> /sys/class/typec/port0-partner/port0-partner.0/active      no
> /sys/class/typec/port0-partner/supports_usb_power_delivery no
> 
> The port lists only the 8087 alternate mode, with no ff01 entry, although
> the platform drives DP over this port at boot. There is no INTC1043 (PMC
> mux) ACPI device, and intel_pmc_mux is not loaded.

The muxes are handled in FW. The UCSI on your system is only an
"optional" status interface. You have no real control over the ports
from the operating system, and as we can see, even the status
information is unreliable.

> Hotplug on 7.2.3-arch1-3, 2026-10-05:
> 
>   usb 3-3: USB disconnect, device number 2
>   usb 3-3: new full-speed USB device number 6 using xhci_hcd
>   ucsi_acpi USBC000:00: unknown error 0
>   ucsi_acpi USBC000:00: con1: failed to register partner alt modes (-5)
>   usb 3-3: not running at top speed; connect to a high speed hub
>   usb 3-3: New USB device found, idVendor=05e3, idProduct=0f01, bcdDevice=
> 1.00
>   usb 3-3: Product: Billboard Device
>   ucsi_acpi USBC000:00: unknown error 0
>   ucsi_acpi USBC000:00: con1: failed to register partner alt modes (-5)
> 
> Boot with the cable connected (display works, same error logged):
> 
>   usb 3-3: New USB device found, idVendor=05e3, idProduct=0f01, bcdDevice=
> 1.00
>   typec port0: bound usb3-port3 (ops connector_ops)
>   typec port0: bound usb2-port1 (ops connector_ops)
>   ucsi_acpi USBC000:00: unknown error 0
>   ucsi_acpi USBC000:00: unknown error 0
>   ucsi_acpi USBC000:00: con1: failed to register partner alt modes (-5)
> 
> Earlier the same day on 7.2.5, the first plug event logged:
> 
>   ucsi_acpi USBC000:00: ucsi_handle_connector_change: GET_CONNECTOR_STATUS
> failed (-110)
>   ucsi_acpi USBC000:00: possible UCSI driver bug 1
>   ucsi_acpi USBC000:00: failed to re-enable notifications (-22)
>   ucsi_acpi USBC000:00: unknown error 0
>   ucsi_acpi USBC000:00: con1: failed to register partner alt modes (-5)
> 
> "unknown error 0" also appears once at boot without anything plugged in.
> 
> Is the OS expected to trigger DP mode entry on this platform, and if so,
> through which interface? I can run debug patches, enable dynamic debug for
> typec_ucsi and ucsi_acpi, or dump the ACPI tables if that helps.

The operating system has no control over the alternate modes on this
system. It's all handled in firmware.

Let's make sure that the ucsi drive is not having any effect with this
issue. Please remove the ucsi module completely, and then reproduce
the issue. There should be no difference.

If that's the case then we simply can't do anything from the operating
system to improve the situation unfortunately. The firmware has to be
fixed.

Thanks,

-- 
heikki