drm/i915: Record fence registers on error.

Having seen the effects of erroneous fencing on the batchbuffer, a
useful sanity check is to record the fence registers at the time of an
error.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -684,6 +684,9 @@ static int i915_error_state(struct seq_file *m, void *unused)
 	seq_printf(m, "  INSTPM: 0x%08x\n", error->instpm);
 	seq_printf(m, "  seqno: 0x%08x\n", error->seqno);
 
+	for (i = 0; i < 16; i++)
+		seq_printf(m, "  fence[%d] = %08llx\n", i, error->fence[i]);
+
 	if (error->active_bo)
 		print_error_buffers(m, "Active",
 				    error->active_bo,

drivers/gpu/drm/i915/i915_drv.h

@@ -166,6 +166,7 @@ struct drm_i915_error_state {
 	u32 instdone1;
 	u32 seqno;
 	u64 bbaddr;
+	u64 fence[16];
 	struct timeval time;
 	struct drm_i915_error_object {
 		int page_count;

drivers/gpu/drm/i915/i915_irq.c

@@ -581,6 +581,35 @@ static u32 capture_bo_list(struct drm_i915_error_buffer *err,
 	return i;
 }
 
+static void i915_gem_record_fences(struct drm_device *dev,
+				   struct drm_i915_error_state *error)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	int i;
+
+	/* Fences */
+	switch (INTEL_INFO(dev)->gen) {
+	case 6:
+		for (i = 0; i < 16; i++)
+			error->fence[i] = I915_READ64(FENCE_REG_SANDYBRIDGE_0 + (i * 8));
+		break;
+	case 5:
+	case 4:
+		for (i = 0; i < 16; i++)
+			error->fence[i] = I915_READ64(FENCE_REG_965_0 + (i * 8));
+		break;
+	case 3:
+		if (IS_I945G(dev) || IS_I945GM(dev) || IS_G33(dev))
+			for (i = 0; i < 8; i++)
+				error->fence[i+8] = I915_READ(FENCE_REG_945_8 + (i * 4));
+	case 2:
+		for (i = 0; i < 8; i++)
+			error->fence[i] = I915_READ(FENCE_REG_830_0 + (i * 4));
+		break;
+
+	}
+}
+
 /**
  * i915_capture_error_state - capture an error record for later analysis
  * @dev: drm device
@@ -656,6 +685,7 @@ static void i915_capture_error_state(struct drm_device *dev)
 		error->acthd = I915_READ(ACTHD);
 		error->bbaddr = 0;
 	}
+	i915_gem_record_fences(dev, error);
 
 	bbaddr = i915_ringbuffer_last_batch(dev, &dev_priv->render_ring);