5.4.0-56: External Display not recognized

[Mathias GW]

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.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1906452

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Rejohn Cuares (rcuares)]

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

[Launchpad Janitor (janitor)]

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