drm/i915: catch forcewake reference underruns

Without this the new drv_suspend/forcewake subtest I've created
doesn't result in immediately visible failures.

Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index ab5165c66381ce62415cd0220c8975e1fb78e320..c3832d9270a608ef143770341a2f8d093b8b7115 100644 (file)
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -280,12 +280,17 @@ void vlv_force_wake_put(struct drm_i915_private *dev_priv,
 
        spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
 
-       if (fw_engine & FORCEWAKE_RENDER &&
-           --dev_priv->uncore.fw_rendercount != 0)
-               fw_engine &= ~FORCEWAKE_RENDER;
-       if (fw_engine & FORCEWAKE_MEDIA &&
-           --dev_priv->uncore.fw_mediacount != 0)
-               fw_engine &= ~FORCEWAKE_MEDIA;
+       if (fw_engine & FORCEWAKE_RENDER) {
+               WARN_ON(!dev_priv->uncore.fw_rendercount);
+               if (--dev_priv->uncore.fw_rendercount != 0)
+                       fw_engine &= ~FORCEWAKE_RENDER;
+       }
+
+       if (fw_engine & FORCEWAKE_MEDIA) {
+               WARN_ON(!dev_priv->uncore.fw_mediacount);
+               if (--dev_priv->uncore.fw_mediacount != 0)
+                       fw_engine &= ~FORCEWAKE_MEDIA;
+       }
 
        if (fw_engine)
                dev_priv->uncore.funcs.force_wake_put(dev_priv, fw_engine);
@@ -301,6 +306,8 @@ static void gen6_force_wake_timer(unsigned long arg)
        assert_device_not_suspended(dev_priv);
 
        spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
+       WARN_ON(!dev_priv->uncore.forcewake_count);
+
        if (--dev_priv->uncore.forcewake_count == 0)
                dev_priv->uncore.funcs.force_wake_put(dev_priv, FORCEWAKE_ALL);
        spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
@@ -452,6 +459,8 @@ void gen6_gt_force_wake_put(struct drm_i915_private *dev_priv, int fw_engine)
 
 
        spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
+       WARN_ON(!dev_priv->uncore.forcewake_count);
+
        if (--dev_priv->uncore.forcewake_count == 0) {
                dev_priv->uncore.forcewake_count++;
                delayed = true;