drm/i915: fix module unload after context merge

commit 8e96d9c4d9843f00ebeb4a9b33596d96602ea101
Author: Ben Widawsky <ben@bwidawsk.net>
Date:   Mon Jun 4 14:42:56 2012 -0700

    drm/i915: reset the GPU on context fini

broke module unload because it reset the gpu before we've stopped
touching it. Later on in the unload sequence the ringbuffer code
complained that the gpu would idle properly (because intel_gpu_reset
only resets the hw and not our sw state).

v2: Reorder things so that we reset the gpu _before_ we release the
backing storage of the default context.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=51183
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_dma.c

@@ -1669,7 +1669,6 @@ int i915_driver_unload(struct drm_device *dev)
 	if (ret)
 		DRM_ERROR("failed to idle hardware: %d\n", ret);
 	i915_gem_retire_requests(dev);
-	i915_gem_context_fini(dev);
 	mutex_unlock(&dev->struct_mutex);
 
 	/* Cancel the retire work handler, which should be idle now. */
@@ -1720,6 +1719,7 @@ int i915_driver_unload(struct drm_device *dev)
 		mutex_lock(&dev->struct_mutex);
 		i915_gem_free_all_phys_object(dev);
 		i915_gem_cleanup_ringbuffer(dev);
+		i915_gem_context_fini(dev);
 		mutex_unlock(&dev->struct_mutex);
 		i915_gem_cleanup_aliasing_ppgtt(dev);
 		i915_gem_cleanup_stolen(dev);

drivers/gpu/drm/i915/i915_gem_context.c

@@ -277,11 +277,14 @@ void i915_gem_context_fini(struct drm_device *dev)
 	if (dev_priv->hw_contexts_disabled)
 		return;
 
+	/* The only known way to stop the gpu from accessing the hw context is
+	 * to reset it. Do this as the very last operation to avoid confusing
+	 * other code, leading to spurious errors. */
+	intel_gpu_reset(dev);
+
 	i915_gem_object_unpin(dev_priv->ring[RCS].default_context->obj);
 
 	do_destroy(dev_priv->ring[RCS].default_context);
-
-	intel_gpu_reset(dev);
 }
 
 void i915_gem_context_open(struct drm_device *dev, struct drm_file *file)