From: Daniel Vetter Date: Wed, 12 Sep 2012 21:24:09 +0000 (+0200) Subject: drm/i915: rip out early dp port write for gm45/ilk X-Git-Tag: omap-for-v3.7-rc1/fixes-cpufreq-signed~20^2~14^2~25 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fba92150aa9959b8f1fa39455315f5e8c59bb702;p=pandora-kernel.git drm/i915: rip out early dp port write for gm45/ilk It's bogus. If I've followed the history of this piece of code correctly, i.e. the initial register write with the following vblank wait, this goes all the way back to the original enabling of DP support in commit a4fc5ed69817c73e32571ad7837bb707f9890009 Author: Keith Packard Date: Tue Apr 7 16:16:42 2009 -0700 drm/i915: Add Display Port support Unfortunately it seems to be nothing more than glorified duct-tape and sometimes actively harmful. Adam Jackson noticed this for CPT platforms with commit e85194641bec56179dcf5e1704ce5c6bf30340c6 Author: Adam Jackson Date: Thu Jul 21 17:48:38 2011 -0400 drm/i915/dp: Don't turn CPT DP ports on too early Unfortunately this kept the code around for ilk and gm45. The specific failure case I'm seeing here is that after a dpms off/on cycle we have the bits from the last link training (hopefully successful link training) set in intel_dp->DP. This is requiered so that complete_link_train can enable the port with the right tuning values. Unfortunately writing these again to the disabled port at dpms on time kills the port somehow until it's disabled - dp link training fails in an endless loop without this patch on my mobile ilk and gm45. Cc: Chris Wilson Tested-by: Chris Wilson Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=51493 Signed-Off-by: Daniel Vetter --- Reading git-diff-tree failed