[PATCH] drm/i915: hangcheck timeout for debugfs

[Ben Widawsky <ben@bwidawsk.net>]

Provide a user accessible way to change the hangcheck timer. This is
useful mostly for disabling the timer completely (value <= 0).

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Cc: Keith Packard <keithp@keithp.com>
---
 drivers/gpu/drm/i915/i915_debugfs.c |   88 +++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_dma.c     |    1 +
 drivers/gpu/drm/i915/i915_drv.h     |    1 +
 drivers/gpu/drm/i915/i915_gem.c     |    7 ++-
 drivers/gpu/drm/i915/i915_irq.c     |   17 +++++--
 5 files changed, 107 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 4d46441..b6582de 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1395,6 +1395,88 @@ static int i915_forcewake_create(struct dentry *root, struct drm_minor *minor)
 	return drm_add_fake_info_node(minor, ent, &i915_forcewake_fops);
 }
 
+static int i915_hangcheck_open(struct inode *inode, struct file *file)
+{
+	file->private_data = inode->i_private;
+	return 0;
+}
+
+static ssize_t i915_hangcheck_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[7];
+	int len, timeout;
+
+	timeout = atomic_read(&dev_priv->hangcheck_timeout);
+	len = snprintf(buf, sizeof(buf), "%d\n", timeout);
+
+	return simple_read_from_buffer(ubuf, max, ppos, buf, len);
+}
+
+static ssize_t i915_hangcheck_write(struct file *filp,
+				    const char __user *ubuf,
+				    size_t cnt,
+				    loff_t *ppos)
+{
+	struct drm_device *dev = filp->private_data;
+	drm_i915_private_t *dev_priv = dev->dev_private;
+	char buf[7]; /* 99.9 seconds max */
+	int new_timeout = 0;
+	int ret;
+
+	if (cnt > 0) {
+		if (cnt > sizeof (buf) - 1)
+			return -EINVAL;
+
+		if (copy_from_user(buf, ubuf, cnt))
+			return -EFAULT;
+		buf[cnt] = 0;
+
+		new_timeout = simple_strtol(buf, NULL, 0);
+	}
+
+	ret = mutex_lock_interruptible(&dev->struct_mutex);
+	if (ret)
+		return ret;
+
+	if (new_timeout <= 0) {
+		new_timeout = 0;
+		del_timer_sync(&dev_priv->hangcheck_timer);
+	}
+
+	atomic_set(&dev_priv->hangcheck_timeout, new_timeout);
+
+	mutex_unlock(&dev->struct_mutex);
+
+	return cnt;
+}
+
+static const struct file_operations i915_hangcheck_fops = {
+	.owner = THIS_MODULE,
+	.open = i915_hangcheck_open,
+	.read = i915_hangcheck_read,
+	.write = i915_hangcheck_write,
+};
+
+static int i915_hangcheck_create(struct dentry *root, struct drm_minor *minor)
+{
+	struct drm_device *dev = minor->dev;
+	struct dentry *ent;
+
+	ent = debugfs_create_file("i915_hangcheck_timeout",
+				  S_IRUGO | S_IWUSR,
+				  root, dev,
+				  &i915_hangcheck_fops);
+	if (IS_ERR(ent))
+		return PTR_ERR(ent);
+
+	return drm_add_fake_info_node(minor, ent, &i915_hangcheck_fops);
+}
+
 static struct drm_info_list i915_debugfs_list[] = {
 	{"i915_capabilities", i915_capabilities, 0},
 	{"i915_gem_objects", i915_gem_object_info, 0},
@@ -1448,6 +1530,10 @@ int i915_debugfs_init(struct drm_minor *minor)
 	if (ret)
 		return ret;
 
+	ret = i915_hangcheck_create(minor->debugfs_root, minor);
+	if (ret)
+		return ret;
+
 	return drm_debugfs_create_files(i915_debugfs_list,
 					I915_DEBUGFS_ENTRIES,
 					minor->debugfs_root, minor);
@@ -1457,6 +1543,8 @@ void i915_debugfs_cleanup(struct drm_minor *minor)
 {
 	drm_debugfs_remove_files(i915_debugfs_list,
 				 I915_DEBUGFS_ENTRIES, minor);
+	drm_debugfs_remove_files((struct drm_info_list *) &i915_hangcheck_fops,
+				 1, minor);
 	drm_debugfs_remove_files((struct drm_info_list *) &i915_forcewake_fops,
 				 1, minor);
 	drm_debugfs_remove_files((struct drm_info_list *) &i915_wedged_fops,
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 0239e99..e44a4a6 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -2092,6 +2092,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 
 	setup_timer(&dev_priv->hangcheck_timer, i915_hangcheck_elapsed,
 		    (unsigned long) dev);
+	atomic_set(&dev_priv->hangcheck_timeout, DRM_I915_HANGCHECK_PERIOD);
 
 	spin_lock(&mchdev_lock);
 	i915_mch_dev = dev_priv;
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 8a9fd91..f518e76 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -320,6 +320,7 @@ typedef struct drm_i915_private {
 #define DRM_I915_HANGCHECK_PERIOD 1500 /* in ms */
 	struct timer_list hangcheck_timer;
 	int hangcheck_count;
+	atomic_t hangcheck_timeout;
 	uint32_t last_acthd;
 	uint32_t last_instdone;
 	uint32_t last_instdone1;
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index cb1f61d..48b140e 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1777,8 +1777,11 @@ i915_add_request(struct intel_ring_buffer *ring,
 	ring->outstanding_lazy_request = false;
 
 	if (!dev_priv->mm.suspended) {
-		mod_timer(&dev_priv->hangcheck_timer,
-			  jiffies + msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
+		int timeout = atomic_read(&dev_priv->hangcheck_timeout);
+		if (timeout) {
+			mod_timer(&dev_priv->hangcheck_timer, jiffies +
+				msecs_to_jiffies(timeout));
+		}
 		if (was_empty)
 			queue_delayed_work(dev_priv->wq,
 					   &dev_priv->mm.retire_work, HZ);
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index b9fafe3..20316d3 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -352,6 +352,7 @@ static void notify_ring(struct drm_device *dev,
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	u32 seqno;
+	int timeout;
 
 	if (ring->obj == NULL)
 		return;
@@ -362,9 +363,12 @@ static void notify_ring(struct drm_device *dev,
 	ring->irq_seqno = seqno;
 	wake_up_all(&ring->irq_queue);
 
-	dev_priv->hangcheck_count = 0;
-	mod_timer(&dev_priv->hangcheck_timer,
-		  jiffies + msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
+	timeout = atomic_read(&dev_priv->hangcheck_timeout);
+	if (timeout) {
+		dev_priv->hangcheck_count = 0;
+		mod_timer(&dev_priv->hangcheck_timer, jiffies +
+			  msecs_to_jiffies(timeout));
+	}
 }
 
 static void gen6_pm_rps_work(struct work_struct *work)
@@ -1721,9 +1725,12 @@ void i915_hangcheck_elapsed(unsigned long data)
 	}
 
 repeat:
+	/* should never be 0, we should drain the timer before setting * to 0 */
+	WARN_ON(atomic_read(&dev_priv->hangcheck_timeout) == 0);
+
 	/* Reset timer case chip hangs without another request being added */
-	mod_timer(&dev_priv->hangcheck_timer,
-		  jiffies + msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
+	mod_timer(&dev_priv->hangcheck_timer, jiffies +
+		  msecs_to_jiffies(atomic_read(&dev_priv->hangcheck_timeout));
 }
 
 /* drm_dma.h hooks
-- 
1.7.5.2