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>

1 files changed, 28 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
index 707d49c12638..b431b6733cc1 100644
--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -1272,6 +1272,34 @@ out:
 	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