drm/i915: Add debugfs file to clear FIFO underruns.

Adding a i915_fifo_underrun_reset debugfs file will make it possible
for IGT tests to clear FIFO underrun fallout at the start of each
subtest, and make re-enable FBC so tests always have maximum exposure
to features used by IGT. FIFO underruns and FBC bugs will no longer
hide when an earlier subtests disables both.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
References: https://bugs.freedesktop.org/show_bug.cgi?id=105685
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105681
Link: https://patchwork.freedesktop.org/patch/msgid/20180328100526.36467-1-maarten.lankhorst@linux.intel.com
Acked-by: Jani Nikula <jani.nikula@linux.intel.com>
[mlankhorst: Reset FBC reason if underrun had occurred. (vivijim)]
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -4732,6 +4732,67 @@ static int i915_drrs_ctl_set(void *data, u64 val)
 
 DEFINE_SIMPLE_ATTRIBUTE(i915_drrs_ctl_fops, NULL, i915_drrs_ctl_set, "%llu\n");
 
+static ssize_t
+i915_fifo_underrun_reset_write(struct file *filp,
+			       const char __user *ubuf,
+			       size_t cnt, loff_t *ppos)
+{
+	struct drm_i915_private *dev_priv = filp->private_data;
+	struct intel_crtc *intel_crtc;
+	struct drm_device *dev = &dev_priv->drm;
+	int ret;
+	bool reset;
+
+	ret = kstrtobool_from_user(ubuf, cnt, &reset);
+	if (ret)
+		return ret;
+
+	if (!reset)
+		return cnt;
+
+	for_each_intel_crtc(dev, intel_crtc) {
+		struct drm_crtc_commit *commit;
+		struct intel_crtc_state *crtc_state;
+
+		ret = drm_modeset_lock_single_interruptible(&intel_crtc->base.mutex);
+		if (ret)
+			return ret;
+
+		crtc_state = to_intel_crtc_state(intel_crtc->base.state);
+		commit = crtc_state->base.commit;
+		if (commit) {
+			ret = wait_for_completion_interruptible(&commit->hw_done);
+			if (!ret)
+				ret = wait_for_completion_interruptible(&commit->flip_done);
+		}
+
+		if (!ret && crtc_state->base.active) {
+			DRM_DEBUG_KMS("Re-arming FIFO underruns on pipe %c\n",
+				      pipe_name(intel_crtc->pipe));
+
+			intel_crtc_arm_fifo_underrun(intel_crtc, crtc_state);
+		}
+
+		drm_modeset_unlock(&intel_crtc->base.mutex);
+
+		if (ret)
+			return ret;
+	}
+
+	ret = intel_fbc_reset_underrun(dev_priv);
+	if (ret)
+		return ret;
+
+	return cnt;
+}
+
+static const struct file_operations i915_fifo_underrun_reset_ops = {
+	.owner = THIS_MODULE,
+	.open = simple_open,
+	.write = i915_fifo_underrun_reset_write,
+	.llseek = default_llseek,
+};
+
 static const struct drm_info_list i915_debugfs_list[] = {
 	{"i915_capabilities", i915_capabilities, 0},
 	{"i915_gem_objects", i915_gem_object_info, 0},
@@ -4799,6 +4860,7 @@ static const struct i915_debugfs_files {
 	{"i915_error_state", &i915_error_state_fops},
 	{"i915_gpu_info", &i915_gpu_info_fops},
 #endif
+	{"i915_fifo_underrun_reset", &i915_fifo_underrun_reset_ops},
 	{"i915_next_seqno", &i915_next_seqno_fops},
 	{"i915_display_crc_ctl", &i915_display_crc_ctl_fops},
 	{"i915_pri_wm_latency", &i915_pri_wm_latency_fops},

drivers/gpu/drm/i915/intel_display.c

@@ -13019,10 +13019,25 @@ static void intel_begin_crtc_commit(struct drm_crtc *crtc,
 							   intel_cstate);
 }
 
+void intel_crtc_arm_fifo_underrun(struct intel_crtc *crtc,
+				  struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
+
+	if (!IS_GEN2(dev_priv))
+		intel_set_cpu_fifo_underrun_reporting(dev_priv, crtc->pipe, true);
+
+	if (crtc_state->has_pch_encoder) {
+		enum pipe pch_transcoder =
+			intel_crtc_pch_transcoder(crtc);
+
+		intel_set_pch_fifo_underrun_reporting(dev_priv, pch_transcoder, true);
+	}
+}
+
 static void intel_finish_crtc_commit(struct drm_crtc *crtc,
 				     struct drm_crtc_state *old_crtc_state)
 {
-	struct drm_i915_private *dev_priv = to_i915(crtc->dev);
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	struct intel_atomic_state *old_intel_state =
 		to_intel_atomic_state(old_crtc_state->state);
@@ -13033,17 +13048,8 @@ static void intel_finish_crtc_commit(struct drm_crtc *crtc,
 
 	if (new_crtc_state->update_pipe &&
 	    !needs_modeset(&new_crtc_state->base) &&
-	    old_crtc_state->mode.private_flags & I915_MODE_FLAG_INHERITED) {
-		if (!IS_GEN2(dev_priv))
-			intel_set_cpu_fifo_underrun_reporting(dev_priv, intel_crtc->pipe, true);
-
-		if (new_crtc_state->has_pch_encoder) {
-			enum pipe pch_transcoder =
-				intel_crtc_pch_transcoder(intel_crtc);
-
-			intel_set_pch_fifo_underrun_reporting(dev_priv, pch_transcoder, true);
-		}
-	}
+	    old_crtc_state->mode.private_flags & I915_MODE_FLAG_INHERITED)
+		intel_crtc_arm_fifo_underrun(intel_crtc, new_crtc_state);
 }
 
 /**

drivers/gpu/drm/i915/intel_drv.h

@@ -1597,6 +1597,8 @@ void hsw_disable_ips(const struct intel_crtc_state *crtc_state);
 enum intel_display_power_domain intel_port_to_power_domain(enum port port);
 void intel_mode_from_pipe_config(struct drm_display_mode *mode,
 				 struct intel_crtc_state *pipe_config);
+void intel_crtc_arm_fifo_underrun(struct intel_crtc *crtc,
+				  struct intel_crtc_state *crtc_state);
 
 int skl_update_scaler_crtc(struct intel_crtc_state *crtc_state);
 int skl_max_scale(struct intel_crtc *crtc, struct intel_crtc_state *crtc_state,
@@ -1784,6 +1786,7 @@ void intel_fbc_flush(struct drm_i915_private *dev_priv,
 		     unsigned int frontbuffer_bits, enum fb_op_origin origin);
 void intel_fbc_cleanup_cfb(struct drm_i915_private *dev_priv);
 void intel_fbc_handle_fifo_underrun_irq(struct drm_i915_private *dev_priv);
+int intel_fbc_reset_underrun(struct drm_i915_private *dev_priv);
 
 /* intel_hdmi.c */
 void intel_hdmi_init(struct drm_i915_private *dev_priv, i915_reg_t hdmi_reg,

drivers/gpu/drm/i915/intel_fbc.c

@@ -1272,6 +1272,34 @@ static void intel_fbc_underrun_work_fn(struct work_struct *work)
 	mutex_unlock(&fbc->lock);
 }
 
+/*
+ * intel_fbc_reset_underrun - reset FBC fifo underrun status.
+ * @dev_priv: i915 device instance
+ *
+ * See intel_fbc_handle_fifo_underrun_irq(). For automated testing we
+ * want to re-enable FBC after an underrun to increase test coverage.
+ */
+int intel_fbc_reset_underrun(struct drm_i915_private *dev_priv)
+{
+	int ret;
+
+	cancel_work_sync(&dev_priv->fbc.underrun_work);
+
+	ret = mutex_lock_interruptible(&dev_priv->fbc.lock);
+	if (ret)
+		return ret;
+
+	if (dev_priv->fbc.underrun_detected) {
+		DRM_DEBUG_KMS("Re-allowing FBC after fifo underrun\n");
+		dev_priv->fbc.no_fbc_reason = "FIFO underrun cleared";
+	}
+
+	dev_priv->fbc.underrun_detected = false;
+	mutex_unlock(&dev_priv->fbc.lock);
+
+	return 0;
+}
+
 /**
  * intel_fbc_handle_fifo_underrun_irq - disable FBC when we get a FIFO underrun
  * @dev_priv: i915 device instance