drm/i915: Fix modeset handling during gpu reset, v5.

This function would call drm_modeset_lock_all, while the suspend/resume
functions already have their own locking. Fix this by factoring out
__intel_display_resume, and calling the atomic helpers for duplicating
atomic state and disabling all crtc's during suspend.

Changes since v1:
- Deal with -EDEADLK right after lock_all and clean up calls
  to hw readout.
- Always take all modeset locks so updates during gpu reset are blocked.
Changes since v2:
- Fix deadlock in intel_update_primary_planes.
- Move WARN_ON(EDEADLK) to __intel_display_resume.
- pctx -> ctx
- only call __intel_display_resume on success in intel_display_resume.
Changes since v3:
- Rebase on top of dev_priv -> dev change.
- Use drm_modeset_lock_all_ctx instead of drm_modeset_lock_all.
Changes since v4 [by vsyrjala]:
- Deal with skip_intermediate_wm
- Update comment w.r.t. mode_config.mutex vs. ->detect()
- Rebase due to INTEL_GEN() etc.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Fixes: e2c8b8701e ("drm/i915: Use atomic helpers for suspend, v2.")
Cc: stable@vger.kernel.org
Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470428910-12125-2-git-send-email-ville.syrjala@linux.intel.com
(cherry picked from commit 7397489399)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -1854,6 +1854,7 @@ struct drm_i915_private {
 	enum modeset_restore modeset_restore;
 	struct mutex modeset_restore_lock;
 	struct drm_atomic_state *modeset_restore_state;
+	struct drm_modeset_acquire_ctx reset_ctx;
 
 	struct list_head vm_list; /* Global list of all address spaces */
 	struct i915_ggtt ggtt; /* VM representing the global address space */