[i915_bdw] Add a patch to fix crashes

[Timo Aaltonen]

We need a new patch from bdw-backports branch to fix a number of crashers in the i915_bdw driver:

commit 17ef4e5850c6fc48a3af2ca89aea19fec7298ace
Author: Ben Widawsky <email address hidden>
Date: Fri May 9 15:09:26 2014 -0700

    drm/i915/bdw: Use MMIO for loading PDPs

    This is a partial-functional backport of:
    commit eeb9488e751a0a6401e7516a893efaf9d1f77fb5
    Author: Ben Widawsky <email address hidden>
    Date: Fri Dec 6 14:11:10 2013 -0800

        drm/i915: Extract mm switching to function

    In that commit, the new mm switching function introduced the ability to
    either load the page tables via the ring, or via MMIO. The issue we have
    is during reset, we do not have the ability to use the rings. Trying to
    do so will fail, and prevent our Aliasing PPGTT from coming back. In
    current upstream, we use the MMIO on reset, and LRI for everything else.

    Here however, we always use the MMIO (in spite of what docs say, I've
    used this for a long time, and it's never *not* worked.). During
    development, we were using MMIO, and it was changed toward the end on
    code review. We do not have enough of the other code in place to be as
    smart as we are for current upstream.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=77587
    Signed-off-by: Ben Widawsky <email address hidden>

[Timo Aaltonen (tjaalton)]

this is fixed in v3.15-rc which utopic seems to have

[Timo Aaltonen (tjaalton)]

Just for reference, the crasher can be reproduced most easily by playing a HD video with vlc. Resume from suspend will also trigger it eventually, but it needs to happen by using the lid, not scripting with fwts or such.

[Timo Aaltonen (tjaalton)]

this is actually fixed by 1321729 in another way