Created attachment 116382 [details] dmesg output when I run 'xrandr --output DP1 --mode 3840x2160' I have a Lenovo ThinkPad X240 with a Intel Graphics HD 4400 [Haswell-ULT GPU 8086:0a16] and I'm running Arch Linux x86_64 with kernel 4.1.0-rc6-drm_intel_nightly_20150607. I've recently got a Dell P2415Q monitor and I can't get 3840x2160@60Hz via Mini DisplayPort to work (right now I'm running 3840x2160@35Hz). When I run "xrandr --output DP1 --mode 3840x2160", I get a "drm:intel_set_cpu_fifo_underrun_reporting" (complete dmesg output attached). Kernel options: video.use_native_backlight=0 i915.enable_ips=0 This looks similtar to https://bugs.freedesktop.org/show_bug.cgi?id=90043 (except that I have a HSW instead of BDW) but the latest drm-intel-nightly did not fix it for me. Any clue on what's going on or plans to fix it? Any other info I can provide to help? Thanks, Tiago
Please add 'drm.debug=0x1e log_buf_len=4M' to your kernel command line and attach full dmesg (from boot).
Created attachment 116395 [details] Full dmesg with drm.debug=0x1e log_buf_len=4M There it goes.
Created attachment 116396 [details] dmesg with monitor MST configuration set to secundary Sorry, it turns out I had MST disabled in my monitor. I enabled MST-secondary and now the output is different (dmesg attached). To start with, xrandr shows me a DP1-8 instead of DP1: Screen 0: minimum 8 x 8, current 5206 x 2160, maximum 32767 x 32767 eDP1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 277mm x 156mm 1366x768 60.00*+ 1024x768 60.00 800x600 60.32 56.25 640x480 59.94 DP1 disconnected (normal left inverted right x axis y axis) DP1-1 disconnected (normal left inverted right x axis y axis) DP1-8 connected 3840x2160+1366+0 (normal left inverted right x axis y axis) 527mm x 296mm 3840x2160 29.98*+ 2560x1440 59.95 2048x1280 59.99 1920x1200 59.88 1920x1080 60.00 60.00 50.00 59.94 30.00 25.00 24.00 29.97 23.98 1600x1200 60.00 1600x900 59.98 1280x1024 75.02 60.02 1152x864 75.00 1280x720 60.00 50.00 59.94 1024x768 75.08 60.00 800x600 75.00 60.32 720x576 50.00 720x480 60.00 59.94 640x480 75.00 60.00 59.94 720x400 70.08 DP2 disconnected (normal left inverted right x axis y axis) HDMI1 disconnected (normal left inverted right x axis y axis) HDMI2 disconnected (normal left inverted right x axis y axis) VIRTUAL1 disconnected (normal left inverted right x axis y axis) However, I still can't get 60Hz. If I change to MST-primary, X crashes. According to the monitor user guide: MST “Off”: Default mode - 4k2k 60Hz with MST function Disabled. “Primary”: Set as primary mode at 4K2K 30Hz with MST (DP out) enabled. “Secondary”: Set as secondary mode at 4K2K 30Hz with MST (DP out) disabled. NOTE: Secondary mode can be set using hot key to switch to DP 1.1 when there is no display. See Troubleshooting. Not sure what configuration the driver expects me to use here. I believe HSW is supposed to support 4k@60Hz with MST enabled, right?
There's been plenty of updates to DP MST code in the past months. Presumed fixed, please reopen if the problem persists with the latest kernels and userspace.
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