ChromeOS Version: R61-9620.0.0
Board: Chell
Additional reqs: 4K monitor connected via HoHo dongle 

--- Case #1 :

What steps will reproduce the problem?
(1) Start ChromeOS

What is the expected result?
External display should be in maximum/preferred mode, which is 3840x2160 60Hz

What happens instead?
It shows that monitor is currently in 3840x2160 mode, but actual mode is 2560x1440 (modeprint and display info)

--- Case #2 :

What steps will reproduce the problem?
(1) Start ChromeOS
(2) Open Display Settings dialog
(3) Change resolution from 3840x2160 to 2560x1440
(4) Change resolution back to 3840x2160

What is the expected result?
Display should change resolution to 2560x1440 and then return back to 3840x2160

What happens instead?
Display stays in 2560x1440 mode and nothing is happening



Please use labels and text to provide additional information.

  modes:
  name refresh (Hz) hdisp hss hse htot vdisp vss vse vtot)
  3840x2160 60 3840 4016 4104 4400 2160 2168 2178 2250 594000 flags: phsync, pvsync; type: preferred, driver
  3840x2160 30 3840 4016 4104 4400 2160 2168 2178 2250 297000 flags: phsync, nvsync; type: driver
  3840x2160 30 3840 4016 4104 4400 2160 2168 2178 2250 297000 flags: phsync, pvsync; type: driver
  3840x2160 30 3840 4016 4104 4400 2160 2168 2178 2250 296703 flags: phsync, pvsync; type: driver
  3840x2160 25 3840 4896 4984 5280 2160 2168 2178 2250 297000 flags: phsync, pvsync; type: driver
  3840x2160 24 3840 5116 5204 5500 2160 2168 2178 2250 297000 flags: phsync, pvsync; type: driver
  3840x2160 24 3840 5116 5204 5500 2160 2168 2178 2250 296703 flags: phsync, pvsync; type: driver
  2560x1440 60 2560 2608 2640 2720 1440 1443 1448 1481 241500 flags: phsync, nvsync; type: driver
  1920x1080 60 1920 2008 2052 2200 1080 1084 1089 1125 148500 flags: phsync, nvsync; type: driver
  1920x1080 60 1920 2008 2052 2200 1080 1084 1089 1125 148500 flags: phsync, pvsync; type: driver
  1920x1080 60 1920 2008 2052 2200 1080 1084 1089 1125 148352 flags: phsync, pvsync; type: driver
  1920x1080i 60 1920 2008 2052 2200 1080 1084 1094 1125 74250 flags: phsync, pvsync, interlace; type: driver
  1920x1080i 60 1920 2008 2052 2200 1080 1084 1094 1125 74176 flags: phsync, pvsync, interlace; type: driver
  1920x1080 30 1920 2008 2052 2200 1080 1084 1089 1125 74250 flags: phsync, pvsync; type: driver
  1920x1080 30 1920 2008 2052 2200 1080 1084 1089 1125 74176 flags: phsync, pvsync; type: driver
  1920x1080 24 1920 2558 2602 2750 1080 1084 1089 1125 74250 flags: phsync, pvsync; type: driver
  1920x1080 24 1920 2558 2602 2750 1080 1084 1089 1125 74176 flags: phsync, pvsync; type: driver
  [...]


tail -f /var/log/ui/ui.LATEST 
[3104:3114:0605/144625.530621:ERROR:crtc_controller.cc(43)] Failed to modeset: crtc=30 connector=53 framebuffer_id=58 mode=3840x2160@60: Numerical result out of range
[3104:3114:0605/144625.530670:ERROR:screen_manager.cc(395)] Failed to modeset controller
[3104:3114:0605/144728.305538:ERROR:crtc_controller.cc(43)] Failed to modeset: crtc=30 connector=53 framebuffer_id=60 mode=3840x2160@60: Numerical result out of range
[3104:3114:0605/144728.305571:ERROR:screen_manager.cc(395)] Failed to modeset controller
[3104:3114:0605/144935.383684:ERROR:crtc_controller.cc(43)] Failed to modeset: crtc=30 connector=53 framebuffer_id=58 mode=3840x2160@60: Numerical result out of range
[3104:3114:0605/144935.383821:ERROR:screen_manager.cc(395)] Failed to modeset controller
[3104:3114:0605/144950.998701:ERROR:crtc_controller.cc(43)] Failed to modeset: crtc=30 connector=53 framebuffer_id=59 mode=3840x2160@60: Numerical result out of range
[3104:3114:0605/144950.998737:ERROR:screen_manager.cc(395)] Failed to modeset controller
[3104:3114:0605/145026.781563:ERROR:crtc_controller.cc(43)] Failed to modeset: crtc=30 connector=53 framebuffer_id=65 mode=3840x2160@60: Numerical result out of range
[3104:3114:0605/145026.781609:ERROR:screen_manager.cc(395)] Failed to modeset controller