[Intel-gfx] [PATCH 1/2] drm/i915: more forcewake lock error info

[Ben Widawsky]

Get some more useful info for debugging backtraces on forcewake
problems. Appropriate debug flags will be required for the drm module.

Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_drv.c |   12 ++++++++----
 drivers/gpu/drm/i915/i915_drv.h |    8 +++++---
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 0defd42..af59811 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -317,13 +317,15 @@ static void __gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
  * be called at the beginning of the sequence followed by a call to
  * gen6_gt_force_wake_put() at the end of the sequence.
  */
-void gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
+int gen6_gt_force_wake_get(struct drm_i915_private *dev_priv)
 {
-	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
+	int ret = WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
 
 	/* Forcewake is atomic in case we get in here without the lock */
 	if (atomic_add_return(1, &dev_priv->forcewake_count) == 1)
 		__gen6_gt_force_wake_get(dev_priv);
+
+	return ret;
 }
 
 static void __gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
@@ -335,12 +337,14 @@ static void __gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
 /*
  * see gen6_gt_force_wake_get()
  */
-void gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
+int gen6_gt_force_wake_put(struct drm_i915_private *dev_priv)
 {
-	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
+	int ret = WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
 
 	if (atomic_dec_and_test(&dev_priv->forcewake_count))
 		__gen6_gt_force_wake_put(dev_priv);
+
+	return ret;
 }
 
 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 8a9fd91..7421eb9 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1362,8 +1362,8 @@ extern void intel_display_print_error_state(struct seq_file *m,
  * must be set to prevent GT core from power down and stale values being
  * returned.
  */
-void gen6_gt_force_wake_get(struct drm_i915_private *dev_priv);
-void gen6_gt_force_wake_put(struct drm_i915_private *dev_priv);
+int gen6_gt_force_wake_get(struct drm_i915_private *dev_priv);
+int gen6_gt_force_wake_put(struct drm_i915_private *dev_priv);
 void __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv);
 
 /* We give fast paths for the really cool registers */
@@ -1376,7 +1376,9 @@ void __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv);
 static inline u##x i915_read##x(struct drm_i915_private *dev_priv, u32 reg) { \
 	u##x val = 0; \
 	if (NEEDS_FORCE_WAKE((dev_priv), (reg))) { \
-		gen6_gt_force_wake_get(dev_priv); \
+		if (gen6_gt_force_wake_get(dev_priv)) { \
+			DRM_DEBUG_DRIVER("unlocked forcewake for 0x%08x\n", reg); \
+		} \
 		val = read##y(dev_priv->regs + reg); \
 		gen6_gt_force_wake_put(dev_priv); \
 	} else { \
-- 
1.7.5.2