Currently, we may simultaneously release the fence register from both
fence_update() and i915_gem_restore_fences(). This is dangerous, so
defer the bookkeeping entirely to i915_gem_restore_fences() when the
device is asleep.
Reported-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_fence_reg.c | 27 +++++++++++++++--------
1 file changed, 18 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_fence_reg.c b/drivers/gpu/drm/i915/i915_gem_fence_reg.c
index e037e94792f3..4331dadc7000 100644
--- a/drivers/gpu/drm/i915/i915_gem_fence_reg.c
+++ b/drivers/gpu/drm/i915/i915_gem_fence_reg.c
@@ -240,6 +240,22 @@ static int fence_update(struct drm_i915_fence_reg *fence,
i915_vma_flush_writes(old);
}
+ /*
+ * We only need to update the register itself if the device is awake.
+ * If the device is currently powered down, we will defer the write
+ * to the runtime resume, see i915_gem_restore_fences().
+ *
+ * This only works for removing the fence register, on acquisition
+ * the caller must hold the rpm wakeref. The fence register must
+ * be cleared before we can use any other fences to ensure that
+ * the new fences do not overlap the elided clears, confusing HW.
+ */
+ wakeref = intel_runtime_pm_get_if_in_use(fence->i915);
+ if (!wakeref) {
+ GEM_BUG_ON(vma);
+ return 0;
+ }
+
if (fence->vma && fence->vma != vma) {
/* Ensure that all userspace CPU access is completed before
* stealing the fence.
@@ -253,15 +269,7 @@ static int fence_update(struct drm_i915_fence_reg *fence,
list_move(&fence->link, &fence->i915->mm.fence_list);
}
- /* We only need to update the register itself if the device is awake.
- * If the device is currently powered down, we will defer the write
- * to the runtime resume, see i915_gem_restore_fences().
- */
- wakeref = intel_runtime_pm_get_if_in_use(fence->i915);
- if (wakeref) {
- fence_write(fence, vma);
- intel_runtime_pm_put(fence->i915, wakeref);
- }
+ fence_write(fence, vma);
if (vma) {
if (fence->vma != vma) {
@@ -272,6 +280,7 @@ static int fence_update(struct drm_i915_fence_reg *fence,
list_move_tail(&fence->link, &fence->i915->mm.fence_list);
}
+ intel_runtime_pm_put(fence->i915, wakeref);
return 0;
}
--
2.20.1
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