Comment 136 for bug 1275794

I tried applying the two patches which you posted on intel-gfx[1], ported to 3.13.

[1] http://article.gmane.org/gmane.comp.freedesktop.xorg.drivers.intel/33737

Using a T540p and an Ultradock, connected to a Dell U2410 via a DisplayPort cable --- and it worked! Not only were there no hangs, but in fact I could enable and disable the external display. The "too many retries" did indeed trigger:

[ 4.152360] [drm] GMBUS [i915 gmbus dpb] timed out, falling back to bit banging on pin 5
...
[ 4.245174] fbcon: inteldrmfb (fb0) is primary device
...
[ 5.952436] [drm:intel_dp_aux_native_write] *ERROR* too many retries, giving up
[ 6.004766] [drm] Enabling RC6 states: RC6 on, RC6p off, RC6pp off
[ 6.129836] Console: switching to colour frame buffer device 240x75
[ 6.134854] i915 0000:00:02.0: fb0: inteldrmfb frame buffer
[ 6.134856] i915 0000:00:02.0: registered panic notifier
[ 6.275753] ACPI: Video Device [VID] (multi-head: yes rom: no post: no)
[ 6.276089] input: Video Bus as /devices/LNXSYSTM:00/device:00/PNP0A08:00/LNXVIDEO:00/input/input11
[ 6.276620] [drm] Initialized i915 1.6.0 20080730 for 0000:00:02.0 on minor 0
[ 6.277149] snd_hda_intel 0000:00:03.0: irq 46 for MSI/MSI-Xdevice

When I tried disabling the external monitor, undocking, and redocking, and then tried enabled the external monitor again, the too many retries did trigger again:

[ 1066.879571] drm: not enough stolen space for compressed buffer (need 33554432 more bytes), disabling. Hint: you may be able to increase stolen memory size in the BIOS to avoid this.
[ 1070.884851] [drm:intel_dp_aux_native_write] *ERROR* too many retries, giving up