drm/i915: debugfs for frontbuffer tracking

Useful to figure out whether stuck bits are due to the frontbuffer
tracking code as opposed to individual consumers (who have their own
bitmask tracking).

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1581,6 +1581,21 @@ static int i915_drpc_info(struct seq_file *m, void *unused)
 		return ironlake_drpc_info(m);
 }
 
+static int i915_frontbuffer_tracking(struct seq_file *m, void *unused)
+{
+	struct drm_info_node *node = m->private;
+	struct drm_device *dev = node->minor->dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	seq_printf(m, "FB tracking busy bits: 0x%08x\n",
+		   dev_priv->fb_tracking.busy_bits);
+
+	seq_printf(m, "FB tracking flip bits: 0x%08x\n",
+		   dev_priv->fb_tracking.flip_bits);
+
+	return 0;
+}
+
 static int i915_fbc_status(struct seq_file *m, void *unused)
 {
 	struct drm_info_node *node = m->private;
@@ -5021,6 +5036,7 @@ static const struct drm_info_list i915_debugfs_list[] = {
 	{"i915_drpc_info", i915_drpc_info, 0},
 	{"i915_emon_status", i915_emon_status, 0},
 	{"i915_ring_freq_table", i915_ring_freq_table, 0},
+	{"i915_frontbuffer_tracking", i915_frontbuffer_tracking, 0},
 	{"i915_fbc_status", i915_fbc_status, 0},
 	{"i915_ips_status", i915_ips_status, 0},
 	{"i915_sr_status", i915_sr_status, 0},