drm/i915: add 'reset' parameter

When bringing up new hardware, or otherwise experimenting, GPU hangs are
a way of life. However, the automatic GPU reset can do more harm than
good under these circumstances, as we may wish to capture a full trace for
debugging.

Based on a patch by Zhenyu Wang.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_drv.c

@@ -49,6 +49,9 @@ module_param_named(powersave, i915_powersave, int, 0600);
 unsigned int i915_lvds_downclock = 0;
 module_param_named(lvds_downclock, i915_lvds_downclock, int, 0400);
 
+bool i915_try_reset = true;
+module_param_named(reset, i915_try_reset, bool, 0600);
+
 static struct drm_driver driver;
 extern int intel_agp_enabled;
 
@@ -475,6 +478,9 @@ int i915_reset(struct drm_device *dev, u8 flags)
 	bool need_display = true;
 	int ret;
 
+	if (!i915_try_reset)
+		return 0;
+
 	if (!mutex_trylock(&dev->struct_mutex))
 		return -EBUSY;