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Bug 1519500 - Flickering external displays on Lenovo T460
Summary: Flickering external displays on Lenovo T460
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: kernel
Version: 7.4
Hardware: Unspecified
OS: Unspecified
Target Milestone: rc
: ---
Assignee: Lyude
QA Contact: Desktop QE
Depends On:
TreeView+ depends on / blocked
Reported: 2017-11-30 19:10 UTC by Paul Gozart
Modified: 2018-06-15 22:18 UTC (History)
2 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Last Closed: 2018-05-16 20:17:19 UTC
Target Upstream Version:

Attachments (Terms of Use)

Description Paul Gozart 2017-11-30 19:10:12 UTC
Description of problem:
Customer says, "i have a problem attaching external displays to the Lenovo T460 sometimes. After booting the T460 to the Desktop and starting to attach the both displays one after the other i sometimes end with two flickering external displays. I can't reproduce this problem always but in most cases it happens when attaching the Display Port first and after that the HDMI display.  Doing it in the reverse order (HDMI and than the DP) doesn't seem to cause any problems. Booting the T460 with both displays attached works fine too."

Version-Release number of selected component (if applicable):
RHEL 7.4 Workstation

How reproducible:

Steps to Reproduce:
1.  Boot up RHEL 7.4 Workstation on a Lenovo T460
2.  Plug in external monitor via Display Port first
3.  Plug in external monitor via HDMI second

Actual results:
Both monitors flicker 

Expected results:
Neither monitor flickers regardless of order attached

Additional info:

Comment 2 Lyude 2018-01-27 00:15:25 UTC
Hi, can you get me the following information?

A full dmesg log with drm.debug=0x6 added to your kernel cmdline
The output of /sys/kernel/debug/dri/0/i915_display_info from after plugging in the monitors
Whether or not the 7.5 beta fixes this issue
A description of what kind of setup you have these monitors hooked up to, along with what kind of monitors we're talking about here. e.g. is it hooked up through a dock, directly to the laptop, through adaptors? etc.

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