drm/i915: add FBC_IN_DBG_MASTER no_fbc_reason

The poor in_dbg_master() check was the only one without a reason
string. Give it a reason string so it won't feel excluded.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -935,6 +935,7 @@ struct i915_fbc {
 		FBC_MODULE_PARAM,
 		FBC_CHIP_DEFAULT, /* disabled by default on this chip */
 		FBC_ROTATION, /* rotation is not supported */
+		FBC_IN_DBG_MASTER, /* kernel debugger is active */
 	} no_fbc_reason;
 
 	bool (*fbc_enabled)(struct drm_i915_private *dev_priv);

drivers/gpu/drm/i915/intel_fbc.c

@@ -471,6 +471,8 @@ const char *intel_no_fbc_reason_str(enum no_fbc_reason reason)
 		return "disabled per chip default";
 	case FBC_ROTATION:
 		return "rotation unsupported";
+	case FBC_IN_DBG_MASTER:
+		return "Kernel debugger is active";
 	default:
 		MISSING_CASE(reason);
 		return "unknown reason";
@@ -755,8 +757,10 @@ static void __intel_fbc_update(struct drm_i915_private *dev_priv)
 	}
 
 	/* If the kernel debugger is active, always disable compression */
-	if (in_dbg_master())
+	if (in_dbg_master()) {
+		set_no_fbc_reason(dev_priv, FBC_IN_DBG_MASTER);
 		goto out_disable;
+	}
 
 	if (intel_fbc_setup_cfb(dev_priv, obj->base.size,
 				drm_format_plane_cpp(fb->pixel_format, 0))) {