In my case setting hdmimhz=297 did the trick.
Hardware:
01:00.0 VGA compatible controller: NVIDIA Corporation GK107M [GeForce GT 650M
Mac Edition] (rev a1) (prog-if 00 [VGA controller])
Subsystem: Apple Inc. GK107M [GeForce GT 650M Mac Edition]
Flags: bus master, fast devsel, latency 0, IRQ 35
Memory at c0000000 (32-bit, non-prefetchable) [size=16M]
Memory at 90000000 (64-bit, prefetchable) [size=256M]
Memory at a0000000 (64-bit, prefetchable) [size=32M]
I/O ports at 2000 [size=128]
Expansion ROM at c1000000 [disabled] [size=512K]
Capabilities: <access denied>
Kernel driver in use: nouveau
Kernel modules: nvidiafb, nouveau
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https://bugs.launchpad.net/bugs/1655421
Title:
nouveau driver being too conservative about HDMI pixel clock, barring
usage of native resolution on 4K displays over HDMI
Status in linux package in Ubuntu:
New
Bug description:
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993311]
[drm:drm_add_edid_modes.part.22 [drm]] HDMI: DVI dual 0, max TMDS clock 300000
kHz
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993315] nouveau 0000:01:00.0:
DRM: native mode from largest: 1920x1080@60
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993342]
[drm:drm_mode_debug_printmodeline [drm]] Modeline 69:"3840x2160" 30 297000 3840
4016 4104 4400 2160 2168 2178 2250 0x48 0x5
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993348]
[drm:drm_mode_prune_invalid [drm]] Not using 3840x2160 mode: CLOCK_HIGH
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993353]
[drm:drm_mode_debug_printmodeline [drm]] Modeline 73:"2560x1440" 60 241500 2560
2608 2640 2720 1440 1443 1448 1481 0x40 0x9
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993358]
[drm:drm_mode_prune_invalid [drm]] Not using 2560x1440 mode: CLOCK_HIGH
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993363]
[drm:drm_mode_debug_printmodeline [drm]] Modeline 104:"3840x2160" 25 297000
3840 4896 4984 5280 2160 2168 2178 2250 0x40 0x5
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993368]
[drm:drm_mode_prune_invalid [drm]] Not using 3840x2160 mode: CLOCK_HIGH
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993373]
[drm:drm_mode_debug_printmodeline [drm]] Modeline 105:"3840x2160" 24 297000
3840 5116 5204 5500 2160 2168 2178 2250 0x40 0x5
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993378]
[drm:drm_mode_prune_invalid [drm]] Not using 3840x2160 mode: CLOCK_HIGH
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993383]
[drm:drm_mode_debug_printmodeline [drm]] Modeline 106:"3840x2160" 30 296703
3840 4016 4104 4400 2160 2168 2178 2250 0x40 0x5
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993387]
[drm:drm_mode_prune_invalid [drm]] Not using 3840x2160 mode: CLOCK_HIGH
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993392]
[drm:drm_mode_debug_printmodeline [drm]] Modeline 116:"3840x2160" 24 296703
3840 5116 5204 5500 2160 2168 2178 2250 0x40 0x5
Jan 10 18:56:03 frode-MacBookPro kernel: [ 4.993397]
[drm:drm_mode_prune_invalid [drm]] Not using 3840x2160 mode: CLOCK_HIGH
However it is perfectly valid to use higher pixel clock on some
graphic cards.
This patch will allow the end-user to adjust the pixel clock with the hdmimhz
kernel parameter until the detection code gets good enough:
https://github.com/torvalds/linux/commit/1a0c96c075bb4517d4ce4fb6750ee0a3cf38714c
This page contains a lot of useful information and lead me to a sollution to
my problem:
https://www.elstel.org/software/hunt-for-4K-UHD-2160p.html.en
I think this is worthy of consideration for backport to the Xenial
kernel as not being able to use the most recent LTS version of Ubuntu
Desktop with current hardware is a drag.
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