drm/i915: Extend debugfs/i915_drop_caches to call i915_gem_shrink_all()

Sometimes we want to explicitly page out all available objects from igt,
i.e. call i915_gem_shrink_all() and check that subsequent operations
succeed. This adds DROP_SHRINK_ALL [0x8] to the set of flags for
debugfs/i915_drop_caches for that purpose.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170308144622.23194-1-chris@chris-wilson.co.ukReviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -4231,11 +4231,13 @@ DEFINE_SIMPLE_ATTRIBUTE(i915_ring_test_irq_fops,
 #define DROP_RETIRE 0x4
 #define DROP_ACTIVE 0x8
 #define DROP_FREED 0x10
+#define DROP_SHRINK_ALL 0x20
 #define DROP_ALL (DROP_UNBOUND	| \
 		  DROP_BOUND	| \
 		  DROP_RETIRE	| \
 		  DROP_ACTIVE	| \
-		  DROP_FREED)
+		  DROP_FREED	| \
+		  DROP_SHRINK_ALL)
 static int
 i915_drop_caches_get(void *data, u64 *val)
 {
@@ -4276,6 +4278,9 @@ i915_drop_caches_set(void *data, u64 val)
 	if (val & DROP_UNBOUND)
 		i915_gem_shrink(dev_priv, LONG_MAX, I915_SHRINK_UNBOUND);
 
+	if (val & DROP_SHRINK_ALL)
+		i915_gem_shrink_all(dev_priv);
+
 unlock:
 	mutex_unlock(&dev->struct_mutex);