[Intel-gfx] [PATCH] drm/i915: catch forcewake reference underruns

[Daniel Vetter]

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

Cc: Mika Kuoppala <mika.kuopp...@intel.com>
Cc: Ben Widawsky <b...@bwidawsk.net>
Cc: Chris Wilson <ch...@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vet...@ffwll.ch>
---
 drivers/gpu/drm/i915/intel_uncore.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c 
b/drivers/gpu/drm/i915/intel_uncore.c
index e6bb421a3dbd..e2e328d86aff 100644
--- 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;
-- 
1.8.5.2

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