drm/i915: Always update the no_fbc_reason when disabling

Provide the reason why we call intel_fbc_deactivate() so that debugging
issues with FBC being delayed is clearer.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180125224122.27480-1-chris@chris-wilson.co.uk
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_fbc.c

@@ -492,7 +492,8 @@ static void intel_fbc_schedule_activation(struct intel_crtc *crtc)
 	schedule_work(&work->work);
 }
 
-static void intel_fbc_deactivate(struct drm_i915_private *dev_priv)
+static void intel_fbc_deactivate(struct drm_i915_private *dev_priv,
+				 const char *reason)
 {
 	struct intel_fbc *fbc = &dev_priv->fbc;
 
@@ -505,6 +506,8 @@ static void intel_fbc_deactivate(struct drm_i915_private *dev_priv)
 
 	if (fbc->active)
 		intel_fbc_hw_deactivate(dev_priv);
+
+	fbc->no_fbc_reason = reason;
 }
 
 static bool multiple_pipes_ok(struct intel_crtc *crtc,
@@ -923,14 +926,15 @@ void intel_fbc_pre_update(struct intel_crtc *crtc,
 {
 	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
 	struct intel_fbc *fbc = &dev_priv->fbc;
+	const char *reason = "update pending";
 
 	if (!fbc_supported(dev_priv))
 		return;
 
 	mutex_lock(&fbc->lock);
 
 	if (!multiple_pipes_ok(crtc, plane_state)) {
-		fbc->no_fbc_reason = "more than one pipe active";
+		reason = "more than one pipe active";
 		goto deactivate;
 	}
 
@@ -940,7 +944,7 @@ void intel_fbc_pre_update(struct intel_crtc *crtc,
 	intel_fbc_update_state_cache(crtc, crtc_state, plane_state);
 
 deactivate:
-	intel_fbc_deactivate(dev_priv);
+	intel_fbc_deactivate(dev_priv, reason);
 unlock:
 	mutex_unlock(&fbc->lock);
 }
@@ -973,9 +977,8 @@ static void __intel_fbc_post_update(struct intel_crtc *crtc)
 	    intel_fbc_reg_params_equal(&old_params, &fbc->params))
 		return;
 
-	intel_fbc_deactivate(dev_priv);
+	intel_fbc_deactivate(dev_priv, "FBC enabled (active or scheduled)");
 	intel_fbc_schedule_activation(crtc);
-	fbc->no_fbc_reason = "FBC enabled (active or scheduled)";
 }
 
 void intel_fbc_post_update(struct intel_crtc *crtc)
@@ -1016,7 +1019,7 @@ void intel_fbc_invalidate(struct drm_i915_private *dev_priv,
 	fbc->busy_bits |= intel_fbc_get_frontbuffer_bit(fbc) & frontbuffer_bits;
 
 	if (fbc->enabled && fbc->busy_bits)
-		intel_fbc_deactivate(dev_priv);
+		intel_fbc_deactivate(dev_priv, "frontbuffer write");
 
 	mutex_unlock(&fbc->lock);
 }
@@ -1246,7 +1249,7 @@ static void intel_fbc_underrun_work_fn(struct work_struct *work)
 	DRM_DEBUG_KMS("Disabling FBC due to FIFO underrun.\n");
 	fbc->underrun_detected = true;
 
-	intel_fbc_deactivate(dev_priv);
+	intel_fbc_deactivate(dev_priv, "FIFO underrun");
 out:
 	mutex_unlock(&fbc->lock);
 }