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Intel — i915: Monitor Detection with Daisy Chaining Requires Improvement

Description

When using monitors with DisplayPort daisy chaining (MST functionality) with Intel graphics processors (e.g., in Celeron, Pentium, Core i3/i5/i7), it's possible to experience occasional monitor-detection variations on Linux systems.

Affected users report that a monitor briefly appears at startup but then disappears — i.e., it's no longer xrandr visible or listed. /sys/class/drm/ as a DisplayPort connection.

Cause

The issue lies in MST (Multi-Stream Transport) support, which the Intel graphics driver enables by default (i915
This feature enables so-called daisy-chaining, in which multiple monitors are connected via a single DisplayPort connection.

However, MST detection shows limited reliability on certain Intel platforms, particularly on:

  • Jasper Lake (e.g., Celeron J6412)

  • Tiger Lake, Gemini Lake, Elkhart Lake

  • Combinations with certain monitors and docking stations

The result:
The driver may not detect the MST topology or complete the EDID (Extended Display Identification Data) query, and individual monitors may appear inactive.

Solution: Disable MST

To ensure reliable monitor detection, disable MST in the Intel driver, even when the monitors support daisy-chaining.

Add the following additional kernel parameter:

i915.enable_dp_mst=0

Important Note on Cabling

Although the monitors technically support daisy chaining, avoid daisy chaining once i915.enable_dp_mst=0 is set.

Instead, connect both monitors directly to separate graphics outputs using their own DisplayPort cables.

This configuration lets the kernel detect and manage the connections correctly.

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