Setup: Lenovo P50, Gentoo Linux, kernel 4.14.X (all same behaviour); one externally connected monitor (HDMI), tried both Dell U2415 and HP z24i. The laptop has one integrated card (Intel) and one discrete card (nvidia)
The behaviour is the following:
Let’s assume that the system boots correctly and both monitors (internal and external) are working fine.
Any change to the configuration, either by removing the external monitor or using the tools to change any monitor configuration (like layout: relative position of the screens, resolution and so on) causes the monitors to flash several times, often without stopping until reboot.
More details:
The behaviour is way more serious when the laptop is on the docking station, hence the external monitor is connected thru the docking station hdmi plug.
On the same machine (dual boot) windows has no issues.
The behaviour happens when changing the layout using kde systemsetting tool or nvidia-settings. In the latter case, also changing the Force Composition switch triggers the issue.
When using the docking station, one way to stop monitor flashing is to hit several times shift/alt/F12, thus disabling and reenabling composition quickly; however if this stops monitors to flash, often the configuration is not the desired one, so the whole process has to be repeated several times.
The beaviour is more evident with the HP monitor and really annoying with the docking station, this leads me to think that the driver has some timing issues (say, the monitor is still settling after configuration change and the driver thinks it is off or something like this).
The behaviour happens both when using only discrete card (via bios) or when using prime setup.
When this happens, logs are full of messages like this:
[ 34.901] (–) NVIDIA(GPU-0): DFP-0: disconnected
[ 34.901] (–) NVIDIA(GPU-0): DFP-0: Internal TMDS
[ 34.901] (–) NVIDIA(GPU-0): DFP-0: 165.0 MHz maximum pixel clock
[ 34.901] (–) NVIDIA(GPU-0):
[ 35.032] (–) NVIDIA(GPU-0): DELL U2415 (DFP-1): connected
[ 35.032] (–) NVIDIA(GPU-0): DELL U2415 (DFP-1): Internal TMDS
[ 35.032] (–) NVIDIA(GPU-0): DELL U2415 (DFP-1): 340.0 MHz maximum pixel clock
[ 35.032] (–) NVIDIA(GPU-0):
[ 35.033] (–) NVIDIA(GPU-0): DFP-2: disconnected
[ 35.033] (–) NVIDIA(GPU-0): DFP-2: Internal TMDS
[ 35.033] (–) NVIDIA(GPU-0): DFP-2: 165.0 MHz maximum pixel clock
[ 35.033] (–) NVIDIA(GPU-0):
[ 35.033] (–) NVIDIA(GPU-0): DFP-3: disconnected
[ 35.033] (–) NVIDIA(GPU-0): DFP-3: Internal DisplayPort
[ 35.033] (–) NVIDIA(GPU-0): DFP-3: 960.0 MHz maximum pixel clock
[ 35.033] (–) NVIDIA(GPU-0):
[ 35.033] (–) NVIDIA(GPU-0): DFP-4: disconnected
[ 35.033] (–) NVIDIA(GPU-0): DFP-4: Internal DisplayPort
[ 35.033] (–) NVIDIA(GPU-0): DFP-4: 960.0 MHz maximum pixel clock
[ 35.033] (–) NVIDIA(GPU-0):
[ 35.033] (–) NVIDIA(GPU-0): DFP-5: disconnected
[ 35.033] (–) NVIDIA(GPU-0): DFP-5: Internal DisplayPort
[ 35.033] (–) NVIDIA(GPU-0): DFP-5: 960.0 MHz maximum pixel clock
[ 35.033] (–) NVIDIA(GPU-0):
[ 36.304] (II) NVIDIA(0): Setting mode “DP-1: nvidia-auto-select @1920x1200 +1920+0 {ViewPortIn=1920x1200, ViewPortOut=1920x1200+0+0}”
[ 36.480] (–) NVIDIA(GPU-0): DFP-0: disconnected
[ 36.480] (–) NVIDIA(GPU-0): DFP-0: Internal TMDS
[ 36.480] (–) NVIDIA(GPU-0): DFP-0: 165.0 MHz maximum pixel clock
[ 36.480] (–) NVIDIA(GPU-0):
[ 36.611] (–) NVIDIA(GPU-0): DELL U2415 (DFP-1): connected
[ 36.611] (–) NVIDIA(GPU-0): DELL U2415 (DFP-1): Internal TMDS
[ 36.611] (–) NVIDIA(GPU-0): DELL U2415 (DFP-1): 340.0 MHz maximum pixel clock
[ 36.611] (–) NVIDIA(GPU-0):
[ 36.612] (–) NVIDIA(GPU-0): DFP-2: disconnected
[ 36.612] (–) NVIDIA(GPU-0): DFP-2: Internal TMDS
[ 36.612] (–) NVIDIA(GPU-0): DFP-2: 165.0 MHz maximum pixel clock
nvidia-bug-report.log.gz (227 KB)