Created attachment 122622 [details]
dmesg with drm.debug=14

I'm using two monitors plugged to a Skylake IGP. This setup works well on Fedora 23, using kernel 4.4.6-300.fc23.x86_64.

I tried Fedora 24 Alpha and noticed that one of the monitor gets black after boot. It happens when the mouse cursor is on that monitor. If I move it to the other monitor the screen output comes back.

I built a 4.6.0-rc1+ kernel from drm-intel-nighlty where the problem can be reproduced. In attachment is a dmesg output booted with drm.debug=14. The monitor gets black just after the "[drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun" message.

When I move the cursor to the other monitor (which brings back the output on my main monitor), I see the "flush pipe" messages at the same time.

Output of /sys/kernel/debug/dri/0/i915_frequency_info if that might help:

PM IER=0x00000070 IMR=0xffffff8f ISR=0x00000000 IIR=0x00000000, MASK=0x80003ffe
GT_PERF_STATUS: 0x00000000
Render p-state ratio: 0
Render p-state VID: 0
Render p-state limit: 23
RPSTAT1: 0x0a808006
RPMODECTL: 0x00000d92
RPINCLIMIT: 0x00002c88
RPDECLIMIT: 0x00004fb0
RPNSWREQ: 350MHz
CAGF: 350MHz
RP CUR UP EI: 196us
RP CUR UP: 75us
RP PREV UP: 0us
Up threshold: 95%
RP CUR DOWN EI: 198us
RP CUR DOWN: 77us
RP PREV DOWN: 0us
Down threshold: 85%
Lowest (RPN) frequency: 350MHz
Nominal (RP1) frequency: 350MHz
Max non-overclocked (RP0) frequency: 1150MHz
Max overclocked frequency: 1150MHz
Current freq: 350 MHz
Actual freq: 350 MHz
Idle freq: 350 MHz
Min freq: 350 MHz
Max freq: 1150 MHz
efficient (RPe) frequency: 350 MHz
Current CD clock frequency: 675000 kHz
Max CD clock frequency: 675000 kHz
Max pixel clock frequency: 675000 kHz