Hello,
I have the same problem. When I upgraded my Ubuntu 18.04.05 LTS system
from Kernel linux-image-5.4.0-53-generic to linux-image-5.4.0-56-generic
my second screen was not detected.
The output of "sudo lshw -c video" had *display-unclaimed" similar to
the output below.
*-display UNCLAIMED
description: VGA compatible controller
product: Kabini [Radeon HD 8400 / R3 Series]
vendor: Advanced Micro Devices, Inc. [AMD/ATI]
physical id: 1
bus info: pci@0000:00:01.0
version: 00
width: 64 bits
clock: 33MHz
The next output is from "sudo lshw -c video" after I reverted to Kernel
linux-image-5.4.0-53-generic.
sudo lshw -c video
*-display
description: VGA compatible controller
product: Kaveri [Radeon R7 Graphics]
vendor: Advanced Micro Devices, Inc. [AMD/ATI]
physical id: 1
bus info: pci@0000:00:01.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
configuration: driver=amdgpu latency=0
resources: irq:49 memory:b0000000-bfffffff memory:d0000000-d07fffff
ioport:f000(size=256) memory:feb00000-feb3ffff memory:feb40000-feb5ffff
*-display
description: VGA compatible controller
product: Oland XT [Radeon HD 8670 / R7 250/350]
vendor: Advanced Micro Devices, Inc. [AMD/ATI]
physical id: 0
bus info: pci@0000:01:00.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
configuration: driver=amdgpu latency=0
resources: irq:52 memory:c0000000-cfffffff memory:fea00000-fea3ffff
ioport:e000(size=256) memory:fea40000-fea5ffff
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https://bugs.launchpad.net/bugs/1906452
Title:
5.4.0-56: External Display not recognized
Status in linux package in Ubuntu:
Incomplete
Bug description:
Machine: Type: Laptop System: Acer product: Aspire A515-44 v: V1.02 serial:
<filter>
Mobo: RO model: Calla_RN v: V1.02 serial: <filter> UEFI: INSYDE v:
1.02
date: 03/23/2020
CPU: Topology: 8-Core model: AMD Ryzen 7 4700U with Radeon Graphics
bits: 64 type: MCP
arch: Zen rev: 1 L2 cache: 4096 KiB
flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 sse4a ssse3
svm bogomips: 31939
Speed: 1397 MHz min/max: 1400/2000 MHz Core speeds (MHz): 1: 1397
2: 1397 3: 1397
4: 1396 5: 1863 6: 1863 7: 1863 8: 4180
Graphics: Device-1: AMD Renoir vendor: Acer Incorporated ALI driver: amdgpu
v: 5.6.0.20.20
bus ID: 05:00.0 chip ID: 1002:1636
Display: x11 server: X.Org 1.20.8 driver: amdgpu,ati unloaded:
fbdev,modesetting,vesa
compositor: marco resolution: 1920x1080~60Hz, 2560x1080~60Hz
OpenGL: renderer: AMD Radeon Graphics v: 4.6.14736 Core Profile
Context 20.20
compat-v: 4.6.14736 direct render: Yes
If I use kernel linux-5.6.0.56, no external display is recognized.
With linux-5.6.0.54 it works.
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