<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div id="yui_3_16_0_1_1453944174350_51636"></div><div id="yiv0167210279yui_3_16_0_1_1453827574538_16712" class=""><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_28834">Hi All,</div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_28870"><br class="" id="yui_3_16_0_1_1453944174350_52364"></div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_28871">My
work recently updated our laptops to a Dell Lattitude E7450 laptop and
accompanying Dell E-Port plus advanced docking station. The machine has</div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_29104">Broadwell
Core I7 processor and integrated graphics. I've tried the latest
Ubuntu 15.10 (kernel version 4.2.0-25) with updated drivers from
01.org, and also running Linux Mint 17.3 based on the 14.4 Ubuntu LTS
release, which runs LInux kernel version 3.19.0-32.</div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_29483"><br class="" id="yui_3_16_0_1_1453944174350_52369"></div><div class="" dir="ltr" id="yiv0167210279yui_3_16_0_1_1453827574538_29604">I
have a 32" external 4k monitor connected to it through DP/miniDP cable.
I have checked that the monitor is set up to use DP 1.2 protocol.</div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_29797" dir="ltr"><br class="" id="yui_3_16_0_1_1453944174350_52373"></div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30081" dir="ltr">The
problem is that when I connect the monitor through the dock using a DP
cable, the monitor can't do 4k resolution. It tops out at 2560x1440 at
60Hz. However, if I connect the monitor directly to the laptop (with or
without the laptop being on the dock), it can drive the full 4k@60Hz.
Moreover, the laptop is able to drive the full 4k resolution on the
Windows 7 operating system, so the issue is definitely some device
driver related. Needless to say, I do not use Windows at all. Note that
I've tried using xrandr on the command line, and also through the GUI
widget that Ubuntu provides.<br class="" id="yui_3_16_0_1_1453944174350_52376"></div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30082" dir="ltr"><br class="" id="yui_3_16_0_1_1453944174350_52379"></div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30184" dir="ltr">When ever I connect/disconnect a monitor, I do get a bunch of warnings about interrupt controller, and FIFO underruns.</div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30408" dir="ltr"><br class="" id="yui_3_16_0_1_1453944174350_52383"></div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30514" dir="ltr"><font class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30754" face="Courier New, courier, monaco, monospace, sans-serif">Jan 25 13:03:53 XXXX kernel: [ 536.304816] [drm:gen8_irq_handler [i915_bpo]] *ERROR* The master control interrupt lied (SDE)!<br class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30528">....</font></div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30529" dir="ltr"><font class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30753" face="Courier New, courier, monaco, monospace, sans-serif">Jan
25 11:41:27 XXXX kernel: [26659.784376]
[drm:intel_cpu_fifo_underrun_irq_handler [i915_bpo]] *ERROR* CPU pipe B
FIFO underrun<br class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30663"></font></div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30872" dir="ltr"><br class="" id="yui_3_16_0_1_1453944174350_52392"></div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30871" dir="ltr"><font class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30978">Any help in resolving this would be appreciated. Is there a pointer to an existing bug report</font><font class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30753">/mailing
list email? I am sure I'll soon get tired of the two step process of
plonking down the laptop on the dock, and then additionally connecting
the display cable to the monitor.<br class="" id="yui_3_16_0_1_1453944174350_52397"></font></div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_31077" dir="ltr"><br class="" id="yui_3_16_0_1_1453944174350_52400"></div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_31182" dir="ltr"><font class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30753">Thanks in advance,</font></div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_31276" dir="ltr"><font class="" id="yiv0167210279yui_3_16_0_1_1453827574538_30753" face="Courier New, courier, monaco, monospace, sans-serif"><br class="" id="yui_3_16_0_1_1453944174350_52406"></font></div><div class="" id="yiv0167210279yui_3_16_0_1_1453827574538_29603"><div id="yui_3_16_0_1_1453944174350_52419" dir="ltr">Pankaj</div></div></div><br></div></body></html>