FS#57605 - [linux] Can't use 144Hz monitor output on 4.15.3-2 with amdgpu DC enabled

Attached to Project: Arch Linux
Opened by Aleksei (nesk_bugs) - Thursday, 22 February 2018, 12:08 GMT
Last edited by Doug Newgard (Scimmia) - Sunday, 15 April 2018, 00:13 GMT
Task Type Bug Report
Category Kernel
Status Closed
Assigned To Tobias Powalowski (tpowa)
Jan Alexander Steffens (heftig)
Architecture All
Severity Low
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 0
Private No

Details

Description:

With DC being turned on (as it is by default) I can't set refresh rate to 144Hz. xrandr -r 144 fails with error, adding a new xrandr mode (as described in wiki) to the output fails as well. If I add amdgpu.dc=0 to kernel boot line (GRUB) - 144Hz is set successfully.

xrand output with amdgpu.dc=1:
DVI-D-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 531mm x 299mm
1920x1080 60.00 + 59.94*

xrand output with amdgpu.dc=0:
DVI-D-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 531mm x 299mm
1920x1080 60.00 + 144.00* 119.98 99.93 59.94


Additional info:
* linux-4.15.3-2
* X.org GPU config attached


Steps to reproduce:
1) Have a Radeon GPU and 144Hz monitor
2) Boot with stock vanilla kernel
3) Try to change refresh rate to 144Hz
   20-amd-only.conf (0.8 KiB)
This task depends upon

Closed by  Doug Newgard (Scimmia)
Sunday, 15 April 2018, 00:13 GMT
Reason for closing:  Fixed
Comment by Aleksei (nesk_bugs) - Saturday, 17 March 2018, 07:02 GMT
Further info: this happens only over DVI link, was reported upstream https://bugs.freedesktop.org/show_bug.cgi?id=103953 and fixed in Alex Deucher's amd-staging-drm-next branch https://cgit.freedesktop.org/~agd5f/linux/?h=amd-staging-drm-next.
Not sure what stable kernel it will end up in, looks like 4.16 - see pull request here https://lists.freedesktop.org/archives/dri-devel/2018-March/168630.html.

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