Description of problem: system is AMD A10-7860 Kaveri on Asus motherboard A88XM-PLUS having DVI, HDMI and VGA display ports. With three displays connected, the VGA display is no longer detected. Typical error messages are: Nov 17 01:35:21 xxxx kernel: [drm:construct [amdgpu]] *ERROR* construct: Invalid Connector ObjectID from Adapter Service for connector index:1! type 0 expected 3 Nov 17 01:35:21 xxxx kernel: [drm:construct [amdgpu]] *ERROR* construct: Invalid Connector ObjectID from Adapter Service for connector index:3! type 0 expected 3 Nov 17 01:35:21 xxxx kernel: [drm:construct [amdgpu]] *ERROR* construct: Invalid Connector ObjectID from Adapter Service for connector index:4! type 0 expected 3 Nov 17 01:35:21 xxxx kernel: [drm:construct [amdgpu]] *ERROR* construct: Invalid Connector ObjectID from Adapter Service for connector index:5! type 0 expected 3 Version-Release number of selected component (if applicable): How reproducible: Every boot with kernel 4.19.2 Steps to Reproduce: 1. boot 2. 3.
Created attachment 10484 [details] boot log from kernel-desktop-4.19.2 What looks like display detection errors can be found at Nov 17 01:35:21 in the log.
Created attachment 10485 [details] boot log from kernel-desktop-4.19.1 Correct display detection is noted in this log at Nov 17 01:27:16
CC: (none) => marja11Assignee: bugsquad => kernel
After reviewing boot logs from October I found the cause of the problem to be the use of the amdgpu.dc=1 parameter setting on the command line. Kernels since version 4.19.1-desktop-4.mga7 (the last one where this parameter was harmless) will fail to detect displays, perhaps just the VGA display, when this parameter is used set to 1. I have now set it to -1 but I do wonder if this is a regression or if my Kaveri is really not meant to use Display Core. This may therefore be nothing more than a workaround and a bug may still exist, but as I do not have the expertise to determine this I have elected to close this bug now. If I have time to do more research I may re-open it.
Status: NEW => RESOLVEDResolution: (none) => FIXED