drm/i915: Use the g4x+ approach on gen2 for handling display stuff around GPU reset

We don't have GPU reset support for gen2, which means the display
hardware is unaffected when a GPU hang is handled. However as the ring
has in fact stopped, any flips still in the ring will never complete,
and thus the display base address updates will never happen. So we
really need to fix that up manually just like we do on g4x+.

In fact, let's just use intel_has_gpu_reset() instead of IS_GEN2()
since that'll also handle cases where someone would disable the GPU
reset support on gen3/4 for whatever reason.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470428910-12125-5-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -3137,7 +3137,8 @@ __intel_display_resume(struct drm_device *dev,
 
 static bool gpu_reset_clobbers_display(struct drm_i915_private *dev_priv)
 {
-	return INTEL_GEN(dev_priv) < 5 && !IS_G4X(dev_priv);
+	return intel_has_gpu_reset(dev_priv) &&
+		INTEL_GEN(dev_priv) < 5 && !IS_G4X(dev_priv);
 }
 
 void intel_prepare_reset(struct drm_i915_private *dev_priv)
@@ -3147,10 +3148,6 @@ void intel_prepare_reset(struct drm_i915_private *dev_priv)
 	struct drm_atomic_state *state;
 	int ret;
 
-	/* no reset support for gen2 */
-	if (IS_GEN2(dev_priv))
-		return;
-
 	/*
 	 * Need mode_config.mutex so that we don't
 	 * trample ongoing ->detect() and whatnot.
@@ -3210,10 +3207,6 @@ void intel_finish_reset(struct drm_i915_private *dev_priv)
 	 */
 	intel_complete_page_flips(dev_priv);
 
-	/* no reset support for gen2 */
-	if (IS_GEN2(dev_priv))
-		return;
-
 	dev_priv->modeset_restore_state = NULL;
 
 	/* reset doesn't touch the display */