Bug 101290 - Radeon R9 390X regression - No output (CVT) or corruption (CVT-R) at 4096x2160@60Hz over DisplayPort
Summary: Radeon R9 390X regression - No output (CVT) or corruption (CVT-R) at 4096x216...
Status: RESOLVED MOVED
Alias: None
Product: DRI
Classification: Unclassified
Component: DRM/Radeon (show other bugs)
Version: unspecified
Hardware: Other All
: medium major
Assignee: Default DRI bug account
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Reported: 2017-06-03 17:21 UTC by freedesktop
Modified: 2019-11-19 09:29 UTC (History)
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Description freedesktop 2017-06-03 17:21:57 UTC 
I had thought I had filed this bug a long time ago on here, but I can't find it...

Graphics card: Radeon R9 390X (Saphhire 11241-04-20G)
Display: LG 31MU97 (via DisplayPort)

With Linux 4.4.x, 4096 x 2160 @ 60 Hz progressive output was working with standard CVT timing.

With Linux 4.5.x onwards, standard CVT timing at that resolution fails (no signal) with the following dmesg output:

kernel: [drm:radeon_dp_link_train [radeon]] *ERROR* channel eq failed
kernel: [drm:radeon_dp_link_train [radeon]] *ERROR* channel eq failed: 5 tries

CVT-R timing results in output, but with a flickering/corrupted full-height band down the right hand side (it approximates the intended output, but pixels seem be to be corrupt in single-pixel horizontal bands and/or flicker in horizontal single-pixel bands) It could be complete coincidence, but the width of the corrupt band seems to be the difference in width vs. 3840x2160, i.e. aobut 256 pixels. With this timing there are no messages in dmesg.

There's a downstream Fedora bug report here: https://bugzilla.redhat.com/show_bug.cgi?id=1353341
Comment 1 Michel Dänzer 2017-06-05 02:41:23 UTC 
Can you bisect between 4.4 and 4.5?
Comment 2 freedesktop 2017-06-05 10:26:55 UTC 
I've tried with a couple of "distro-friendly" bisection approaches so far but run into problems both times, probably partly due to the relative age of the kernels; I can try vanilla bisection but haven't looked into the details of that yet.

Is there anything else I can do that might help identify the problem in the interim, or is bisection the only option?
Comment 3 Martin Peres 2019-11-19 09:29:13 UTC 
-- GitLab Migration Automatic Message --

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