[Intel-gfx] ironlake wierdness bisection result

[Dave Airlie]

Okay I spent today bisecting this and although I'm not 100% sure I got
it right the whole way down, I think where I landed seems sane, so I
said I'd share

This seems to cause the blank rendering zones people have been reporting.

Dave.

commit c07496fa61f4c5cb2addd1c57f6b22fcaeea2eeb
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Fri Apr 13 15:51:51 2012 +0200

drm/i915: don't pwrite tiled objects through the gtt

    ... we will botch up the bit17 swizzling. Furthermore tiled pwrite is
    a (now) unused slowpath, so no one really cares.

    This fixes the last swizzling issues I have with i-g-t on my bit17
    swizzling i915G. No regression, it's been broken since the dawn of
    gem, but it's nice for regression tracking when really _all_ i-g-t
    tests work.

    Actually this is not true, Chris Wilson noticed while reviewing this
    patch that the commit

    commit d9e86c0ee60f323e890484628f351bf50fa9a15d
    Author: Chris Wilson <chris at chris-wilson.co.uk>
    Date:   Wed Nov 10 16:40:20 2010 +0000

        drm/i915: Pipelined fencing [infrastructure]
contained a functional change that broke things.

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter at ffwll.ch>