drm/i915: Disable all outputs early, before KMS takeover

If the outputs are active and continuing to access the GATT when we
teardown the PTEs, then there is a potential for us to hang the GPU.
The hang tends to be a PGTBL_ER with either an invalid host access or
an invalid display plane fetch.

v2: Reorder IRQ initialisation to defer until after GEM is setup.

Reported-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Daniel Vetter <daniel.vetter@ffwll.ch> (855GM)
Tested-by: Pekka Enberg <penberg@kernel.org>
           # note that this doesn't fix the underlying problem of the
             PGTBL_ER and pipe underruns being reported immediately upon
             init on his 965GM MacBook
Reported-and-tested-by: Rick Bramley <richard.bramley@hp.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=35635
Reported-and-tested-by: Zdenek Kabelac <zdenek.kabelac@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=36048
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 7a791f8..4b862f3 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1277,6 +1277,7 @@
 
 /* modesetting */
 extern void intel_modeset_init(struct drm_device *dev);
+extern void intel_modeset_gem_init(struct drm_device *dev);
 extern void intel_modeset_cleanup(struct drm_device *dev);
 extern int intel_modeset_vga_set_state(struct drm_device *dev, bool state);
 extern void i8xx_disable_fbc(struct drm_device *dev);