4 files changed, 73 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index ae68ac1c488..192b27e9046 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1586,6 +1586,64 @@ static const struct file_operations i915_wedged_fops = {
 };
 
 static ssize_t
+i915_ring_stop_read(struct file *filp,
+		    char __user *ubuf,
+		    size_t max,
+		    loff_t *ppos)
+{
+	struct drm_device *dev = filp->private_data;
+	drm_i915_private_t *dev_priv = dev->dev_private;
+	char buf[20];
+	int len;
+
+	len = snprintf(buf, sizeof(buf),
+		       "0x%08x\n", dev_priv->stop_rings);
+
+	if (len > sizeof(buf))
+		len = sizeof(buf);
+
+	return simple_read_from_buffer(ubuf, max, ppos, buf, len);
+}
+
+static ssize_t
+i915_ring_stop_write(struct file *filp,
+		     const char __user *ubuf,
+		     size_t cnt,
+		     loff_t *ppos)
+{
+	struct drm_device *dev = filp->private_data;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	char buf[20];
+	int val = 0;
+
+	if (cnt > 0) {
+		if (cnt > sizeof(buf) - 1)
+			return -EINVAL;
+
+		if (copy_from_user(buf, ubuf, cnt))
+			return -EFAULT;
+		buf[cnt] = 0;
+
+		val = simple_strtoul(buf, NULL, 0);
+	}
+
+	DRM_DEBUG_DRIVER("Stopping rings 0x%08x\n", val);
+
+	mutex_lock(&dev->struct_mutex);
+	dev_priv->stop_rings = val;
+	mutex_unlock(&dev->struct_mutex);
+
+	return cnt;
+}
+
+static const struct file_operations i915_ring_stop_fops = {
+	.owner = THIS_MODULE,
+	.open = simple_open,
+	.read = i915_ring_stop_read,
+	.write = i915_ring_stop_write,
+	.llseek = default_llseek,
+};
+static ssize_t
 i915_max_freq_read(struct file *filp,
 		   char __user *ubuf,
 		   size_t max,
@@ -1885,6 +1943,11 @@ int i915_debugfs_init(struct drm_minor *minor)
 				  &i915_cache_sharing_fops);
 	if (ret)
 		return ret;
+	ret = i915_debugfs_create(minor->debugfs_root, minor,
+				  "i915_ring_stop",
+				  &i915_ring_stop_fops);
+	if (ret)
+		return ret;
 
 	return drm_debugfs_create_files(i915_debugfs_list,
 					I915_DEBUGFS_ENTRIES,
@@ -1903,6 +1966,8 @@ void i915_debugfs_cleanup(struct drm_minor *minor)
 				 1, minor);
 	drm_debugfs_remove_files((struct drm_info_list *) &i915_cache_sharing_fops,
 				 1, minor);
+	drm_debugfs_remove_files((struct drm_info_list *) &i915_ring_stop_fops,
+				 1, minor);
 }
 
 #endif /* CONFIG_DEBUG_FS */
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 8a98f9a1641..90a84f9de8e 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -800,6 +800,8 @@ int i915_reset(struct drm_device *dev, u8 flags)
 	if (!mutex_trylock(&dev->struct_mutex))
 		return -EBUSY;
 
+	dev_priv->stop_rings = 0;
+
 	i915_gem_reset(dev);
 
 	ret = -ENODEV;
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 00a20e985d2..090ec20293f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -412,6 +412,8 @@ typedef struct drm_i915_private {
 	uint32_t last_instdone;
 	uint32_t last_instdone1;
 
+	unsigned int stop_rings;
+
 	unsigned long cfb_size;
 	unsigned int cfb_fb;
 	enum plane cfb_plane;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 38096080a3d..3aabe8dfe5c 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1210,7 +1210,11 @@ int intel_ring_begin(struct intel_ring_buffer *ring,
 
 void intel_ring_advance(struct intel_ring_buffer *ring)
 {
+	struct drm_i915_private *dev_priv = ring->dev->dev_private;
+
 	ring->tail &= ring->size - 1;
+	if (dev_priv->stop_rings & intel_ring_flag(ring))
+		return;
 	ring->write_tail(ring, ring->tail);
 }