[Intel-gfx] regression bisected: display sync drops after 7221fc33

[dann frazier]

I've got a Lenovo T410 w/ an external display (DisplayPort<->HDMI). After
upgrading from a 4.2 kernel to a 4.3, I started hitting an issue where
the display thinks it has lost input for a few moments. Oddly, it
usually happens when I start typing in a terminal after a short period
of inactivity.

I see no OS-side symptoms - there are no new messages in dmesg/syslog/Xorg
log, etc. I reproduced with latest Linus master (@ 3e1e21c7b), and then
bisected down to the following commit:

commit 7221fc333dbe1743a3dff155b03527fda90d4ec1
Author: Matt Roper <matthew.d.roper at intel.com>
Date:   Thu Sep 24 15:53:08 2015 -0700

    drm/i915: Eliminate usage of pipe_wm_parameters from ILK-style WM (v2)
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: not available
URL: <http://lists.freedesktop.org/archives/intel-gfx/attachments/20160125/6264d05a/attachment.sig>