drm/i915: Add GEM debugging Kconfig option

Currently there is a #define to enable extra BUG_ON for debugging
requests and associated activities. I want to expand its use to cover
all of GEM internals (so that we can saturate the code with asserts).
We can add a Kconfig option to make it easier to enable - with the usual
caveats of not enabling unless explicitly requested.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460565315-7748-3-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/Kconfig.debug

@@ -27,3 +27,15 @@ config DRM_I915_DEBUG
 
           If in doubt, say "N".
 
+config DRM_I915_DEBUG_GEM
+        bool "Insert extra checks into the GEM internals"
+        default n
+        depends on DRM_I915_WERROR
+        help
+          Enable extra sanity checks (including BUGs) along the GEM driver
+          paths that may slow the system down and if hit hang the machine.
+
+          Recommended for driver developers only.
+
+          If in doubt, say "N".
+

drivers/gpu/drm/i915/i915_drv.h

@@ -57,6 +57,7 @@
 #include "intel_lrc.h"
 #include "intel_ringbuffer.h"
 
+#include "i915_gem.h"
 #include "i915_gem_gtt.h"
 #include "i915_gem_render_state.h"
 

drivers/gpu/drm/i915/i915_gem.c

@@ -38,8 +38,6 @@
 #include <linux/pci.h>
 #include <linux/dma-buf.h>
 
-#define RQ_BUG_ON(expr)
-
 static void i915_gem_object_flush_gtt_write_domain(struct drm_i915_gem_object *obj);
 static void i915_gem_object_flush_cpu_write_domain(struct drm_i915_gem_object *obj);
 static void
@@ -1521,7 +1519,7 @@ i915_gem_object_wait_rendering(struct drm_i915_gem_object *obj,
 
 			i915_gem_object_retire__read(obj, i);
 		}
-		RQ_BUG_ON(obj->active);
+		GEM_BUG_ON(obj->active);
 	}
 
 	return 0;
@@ -2473,8 +2471,8 @@ void i915_vma_move_to_active(struct i915_vma *vma,
 static void
 i915_gem_object_retire__write(struct drm_i915_gem_object *obj)
 {
-	RQ_BUG_ON(obj->last_write_req == NULL);
-	RQ_BUG_ON(!(obj->active & intel_engine_flag(obj->last_write_req->engine)));
+	GEM_BUG_ON(obj->last_write_req == NULL);
+	GEM_BUG_ON(!(obj->active & intel_engine_flag(obj->last_write_req->engine)));
 
 	i915_gem_request_assign(&obj->last_write_req, NULL);
 	intel_fb_obj_flush(obj, true, ORIGIN_CS);
@@ -2485,8 +2483,8 @@ i915_gem_object_retire__read(struct drm_i915_gem_object *obj, int ring)
 {
 	struct i915_vma *vma;
 
-	RQ_BUG_ON(obj->last_read_req[ring] == NULL);
-	RQ_BUG_ON(!(obj->active & (1 << ring)));
+	GEM_BUG_ON(obj->last_read_req[ring] == NULL);
+	GEM_BUG_ON(!(obj->active & (1 << ring)));
 
 	list_del_init(&obj->engine_list[ring]);
 	i915_gem_request_assign(&obj->last_read_req[ring], NULL);

drivers/gpu/drm/i915/i915_gem.h

@@ -0,0 +1,34 @@
+/*
+ * Copyright © 2016 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ */
+
+#ifndef __I915_GEM_H__
+#define __I915_GEM_H__
+
+#ifdef CONFIG_DRM_I915_DEBUG_GEM
+#define GEM_BUG_ON(expr) BUG_ON(expr)
+#else
+#define GEM_BUG_ON(expr)
+#endif
+
+#endif /* __I915_GEM_H__ */