[PATCH 2/4] drm/i915: Move the forcewake refcounting to a spinlock.

[Eric Anholt <eric@anholt.net>]

We have forcewake in the interrupt handler in the following commit, so
we have to use a spinlock instead of a mutex.

Signed-off-by: Eric Anholt <eric@anholt.net>
---
 drivers/gpu/drm/i915/i915_debugfs.c |    3 +--
 drivers/gpu/drm/i915/i915_dma.c     |    1 +
 drivers/gpu/drm/i915/i915_drv.c     |   17 ++++++++++++-----
 drivers/gpu/drm/i915/i915_drv.h     |    3 ++-
 4 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 51c2257..e62ee5d 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1226,8 +1226,7 @@ static int i915_gen6_forcewake_count_info(struct seq_file *m, void *data)
 	struct drm_device *dev = node->minor->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	seq_printf(m, "forcewake count = %d\n",
-		   atomic_read(&dev_priv->forcewake_count));
+	seq_printf(m, "forcewake count = %d\n", dev_priv->forcewake_count);
 
 	return 0;
 }
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 0239e99..2de4a74 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -2063,6 +2063,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	spin_lock_init(&dev_priv->irq_lock);
 	spin_lock_init(&dev_priv->error_lock);
 	spin_lock_init(&dev_priv->rps_lock);
+	spin_lock_init(&dev_priv->forcewake_lock);
 
 	if (IS_MOBILE(dev) || !IS_GEN2(dev))
 		dev_priv->num_pipe = 2;
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 0defd42..0c46bfc 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -319,11 +319,14 @@ static void __gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
  */
 void gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
 {
-	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
+	unsigned long flags;
 
-	/* Forcewake is atomic in case we get in here without the lock */
-	if (atomic_add_return(1, &dev_priv->forcewake_count) == 1)
+	spin_lock_irqsave(&dev_priv->forcewake_lock, flags);
+
+	if (dev_priv->forcewake_count++ == 0)
 		__gen6_gt_force_wake_get(dev_priv);
+
+	spin_unlock_irqrestore(&dev_priv->forcewake_lock, flags);
 }
 
 static void __gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
@@ -337,10 +340,14 @@ static void __gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
  */
 void gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
 {
-	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
+	unsigned long flags;
 
-	if (atomic_dec_and_test(&dev_priv->forcewake_count))
+	spin_lock_irqsave(&dev_priv->forcewake_lock, flags);
+
+	if (--dev_priv->forcewake_count == 0)
 		__gen6_gt_force_wake_put(dev_priv);
+
+	spin_unlock_irqrestore(&dev_priv->forcewake_lock, flags);
 }
 
 void __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index ee66035..56ef324 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -717,7 +717,8 @@ typedef struct drm_i915_private {
 
 	struct drm_property *broadcast_rgb_property;
 
-	atomic_t forcewake_count;
+	int forcewake_count;
+	spinlock_t forcewake_lock;
 } drm_i915_private_t;
 
 enum i915_cache_level {
-- 
1.7.5.1