External Display Fails to Reconnect After Sleep (Post BIOS update)

[rclendan]

Product: ASUS TUF Gaming Advantage Edition Laptop  (FA617NS)
BIOS Version: 422
Operating Systems Tested: Windows 11 (latest), Linux (Kubuntu 24.04 / Plasma 6 / Wayland + X11)
Issue Summary:
After updating to BIOS 422, the laptop no longer properly re-establishes a connection with an external monitor connected via a USB-C to DisplayPort adapter after the monitor goes to sleep or the laptop suspends. The external display remains undetectable until the cable is physically disconnected and reconnected. This occurs regardless of operating system, cable quality, or power settings.

Steps to Reproduce:

1. Connect an external ultrawide monitor via USB-C to DisplayPort.

2. Allow the monitor to enter sleep mode (either by system suspend or display timeout).

3. Resume the laptop or wake the monitor.

4. Observe that the display remains black or undetected until the cable is unplugged and replugged.

Additional Notes:

• The issue did not occur on previous BIOS versions.

• Tested with high-quality DisplayPort 1.4 active cable (Cable Matters).

• Occurs on both Windows 11 and modern Linux distributions.

• Plasma 6 (Wayland) eliminates input lag issues introduced in BIOS 422, but does not resolve display detection failure.

• Numerous scripting and systemd resume hooks fail to reinitialize display.

• The issue appears to be due to broken Hot Plug Detect or DisplayPort alt-mode re-negotiation logic in BIOS 422.

• BIOS downgrade is locked and not permitted on this model.

Impact:
This breaks external display usability in both professional and development workflows, and severely reduces the functionality of the USB-C DisplayPort feature, especially in docking or dual-monitor environments.

Request:
Please investigate and release a BIOS update to correct Hot Plug Detect (HPD) or DisplayPort link training behavior for USB-C following suspend/resume or display sleep states.

[Anbby_ROG]

Thank you for reporting this issue. Since the latest BIOS version for the FA617NS on our official website is 419, we would like to further confirm if the actual model of your laptop is FA617NT? If the actual model is FA617NT, have you tried using EZ Flash to install BIOS version 419 to test if the issue persists?

Additionally, we would like to ask if this issue occurs with both USB-C ports or only one of them? Does the same problem happen when connecting the display via the HDMI port?

To further clarify the problem, could you please record a video of the issue and provide the following information via private message? We will forward this to the relevant department for confirmation. Thank you for your cooperation.

• Serial Number:
• Windows Build Version: (Settings - System - About)
• iGPU/dGPU Driver Version:
• Display Brand and Model:
• Cable Matters actual model or relevant link: