Revert 190c462d5be19ba622a82f5fd0625087c870a1e6..bf3012ada1b2222e770de5c35c1bb16f73b3a01d"

I shouldn't have pushed this, CI was right - I failed to remove the
BUG_ON(!ops->wait);

Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

drivers/dma-buf/dma-fence-array.c

@@ -104,6 +104,7 @@ const struct dma_fence_ops dma_fence_array_ops = {
 	.get_timeline_name = dma_fence_array_get_timeline_name,
 	.enable_signaling = dma_fence_array_enable_signaling,
 	.signaled = dma_fence_array_signaled,
+	.wait = dma_fence_default_wait,
 	.release = dma_fence_array_release,
 };
 EXPORT_SYMBOL(dma_fence_array_ops);

drivers/dma-buf/dma-fence.c

@@ -158,10 +158,7 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
 		return -EINVAL;
 
 	trace_dma_fence_wait_start(fence);
-	if (fence->ops->wait)
-		ret = fence->ops->wait(fence, intr, timeout);
-	else
-		ret = dma_fence_default_wait(fence, intr, timeout);
+	ret = fence->ops->wait(fence, intr, timeout);
 	trace_dma_fence_wait_end(fence);
 	return ret;
 }
@@ -184,13 +181,6 @@ void dma_fence_release(struct kref *kref)
 }
 EXPORT_SYMBOL(dma_fence_release);
 
-/**
- * dma_fence_free - default release function for &dma_fence.
- * @fence: fence to release
- *
- * This is the default implementation for &dma_fence_ops.release. It calls
- * kfree_rcu() on @fence.
- */
 void dma_fence_free(struct dma_fence *fence)
 {
 	kfree_rcu(fence, rcu);
@@ -506,6 +496,11 @@ dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count,
 	for (i = 0; i < count; ++i) {
 		struct dma_fence *fence = fences[i];
 
+		if (fence->ops->wait != dma_fence_default_wait) {
+			ret = -EINVAL;
+			goto fence_rm_cb;
+		}
+
 		cb[i].task = current;
 		if (dma_fence_add_callback(fence, &cb[i].base,
 					   dma_fence_default_wait_cb)) {
@@ -565,7 +560,7 @@ dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
 	       spinlock_t *lock, u64 context, unsigned seqno)
 {
 	BUG_ON(!lock);
-	BUG_ON(!ops || !ops->wait ||
+	BUG_ON(!ops || !ops->wait || !ops->enable_signaling ||
 	       !ops->get_driver_name || !ops->get_timeline_name);
 
 	kref_init(&fence->refcount);
@@ -577,10 +572,6 @@ dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
 	fence->flags = 0UL;
 	fence->error = 0;
 
-	if (!ops->enable_signaling)
-		set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
-			&fence->flags);
-
 	trace_dma_fence_init(fence);
 }
 EXPORT_SYMBOL(dma_fence_init);

drivers/dma-buf/sw_sync.c

@@ -188,6 +188,7 @@ static const struct dma_fence_ops timeline_fence_ops = {
 	.get_timeline_name = timeline_fence_get_timeline_name,
 	.enable_signaling = timeline_fence_enable_signaling,
 	.signaled = timeline_fence_signaled,
+	.wait = dma_fence_default_wait,
 	.release = timeline_fence_release,
 	.fence_value_str = timeline_fence_value_str,
 	.timeline_value_str = timeline_fence_timeline_value_str,

drivers/gpu/drm/drm_crtc.c

@@ -225,9 +225,16 @@ static const char *drm_crtc_fence_get_timeline_name(struct dma_fence *fence)
 	return crtc->timeline_name;
 }
 
+static bool drm_crtc_fence_enable_signaling(struct dma_fence *fence)
+{
+	return true;
+}
+
 static const struct dma_fence_ops drm_crtc_fence_ops = {
 	.get_driver_name = drm_crtc_fence_get_driver_name,
 	.get_timeline_name = drm_crtc_fence_get_timeline_name,
+	.enable_signaling = drm_crtc_fence_enable_signaling,
+	.wait = dma_fence_default_wait,
 };
 
 struct dma_fence *drm_crtc_create_fence(struct drm_crtc *crtc)

drivers/gpu/drm/drm_syncobj.c

@@ -207,6 +207,7 @@ static const struct dma_fence_ops drm_syncobj_null_fence_ops = {
 	.get_driver_name = drm_syncobj_null_fence_get_name,
 	.get_timeline_name = drm_syncobj_null_fence_get_name,
 	.enable_signaling = drm_syncobj_null_fence_enable_signaling,
+	.wait = dma_fence_default_wait,
 	.release = NULL,
 };
 

drivers/gpu/drm/qxl/qxl_release.c

@@ -50,6 +50,12 @@ static const char *qxl_get_timeline_name(struct dma_fence *fence)
 	return "release";
 }
 
+static bool qxl_nop_signaling(struct dma_fence *fence)
+{
+	/* fences are always automatically signaled, so just pretend we did this.. */
+	return true;
+}
+
 static long qxl_fence_wait(struct dma_fence *fence, bool intr,
 			   signed long timeout)
 {
@@ -113,6 +119,7 @@ signaled:
 static const struct dma_fence_ops qxl_fence_ops = {
 	.get_driver_name = qxl_get_driver_name,
 	.get_timeline_name = qxl_get_timeline_name,
+	.enable_signaling = qxl_nop_signaling,
 	.wait = qxl_fence_wait,
 };
 

drivers/gpu/drm/scheduler/sched_fence.c

@@ -81,6 +81,11 @@ static const char *drm_sched_fence_get_timeline_name(struct dma_fence *f)
 	return (const char *)fence->sched->name;
 }
 
+static bool drm_sched_fence_enable_signaling(struct dma_fence *f)
+{
+	return true;
+}
+
 /**
  * amd_sched_fence_free - free up the fence memory
  *
@@ -129,12 +134,18 @@ static void drm_sched_fence_release_finished(struct dma_fence *f)
 const struct dma_fence_ops drm_sched_fence_ops_scheduled = {
 	.get_driver_name = drm_sched_fence_get_driver_name,
 	.get_timeline_name = drm_sched_fence_get_timeline_name,
+	.enable_signaling = drm_sched_fence_enable_signaling,
+	.signaled = NULL,
+	.wait = dma_fence_default_wait,
 	.release = drm_sched_fence_release_scheduled,
 };
 
 const struct dma_fence_ops drm_sched_fence_ops_finished = {
 	.get_driver_name = drm_sched_fence_get_driver_name,
 	.get_timeline_name = drm_sched_fence_get_timeline_name,
+	.enable_signaling = drm_sched_fence_enable_signaling,
+	.signaled = NULL,
+	.wait = dma_fence_default_wait,
 	.release = drm_sched_fence_release_finished,
 };
 

include/linux/dma-fence.h

@@ -166,8 +166,7 @@ struct dma_fence_ops {
 	 * released when the fence is signalled (through e.g. the interrupt
 	 * handler).
 	 *
-	 * This callback is optional. If this callback is not present, then the
-	 * driver must always have signaling enabled.
+	 * This callback is mandatory.
 	 */
 	bool (*enable_signaling)(struct dma_fence *fence);
 
@@ -191,14 +190,11 @@ struct dma_fence_ops {
 	/**
 	 * @wait:
 	 *
-	 * Custom wait implementation, defaults to dma_fence_default_wait() if
-	 * not set.
+	 * Custom wait implementation, or dma_fence_default_wait.
 	 *
-	 * The dma_fence_default_wait implementation should work for any fence, as long
-	 * as @enable_signaling works correctly. This hook allows drivers to
-	 * have an optimized version for the case where a process context is
-	 * already available, e.g. if @enable_signaling for the general case
-	 * needs to set up a worker thread.
+	 * Must not be NULL, set to dma_fence_default_wait for default implementation.
+	 * the dma_fence_default_wait implementation should work for any fence, as long
+	 * as enable_signaling works correctly.
 	 *
 	 * Must return -ERESTARTSYS if the wait is intr = true and the wait was
 	 * interrupted, and remaining jiffies if fence has signaled, or 0 if wait
@@ -206,7 +202,7 @@ struct dma_fence_ops {
 	 * which should be treated as if the fence is signaled. For example a hardware
 	 * lockup could be reported like that.
 	 *
-	 * This callback is optional.
+	 * This callback is mandatory.
 	 */
 	signed long (*wait)(struct dma_fence *fence,
 			    bool intr, signed long timeout);
@@ -221,6 +217,17 @@ struct dma_fence_ops {
 	 */
 	void (*release)(struct dma_fence *fence);
 
+	/**
+	 * @fill_driver_data:
+	 *
+	 * Callback to fill in free-form debug info.
+	 *
+	 * Returns amount of bytes filled, or negative error on failure.
+	 *
+	 * This callback is optional.
+	 */
+	int (*fill_driver_data)(struct dma_fence *fence, void *data, int size);
+
 	/**
 	 * @fence_value_str:
 	 *
@@ -235,9 +242,8 @@ struct dma_fence_ops {
 	 * @timeline_value_str:
 	 *
 	 * Fills in the current value of the timeline as a string, like the
-	 * sequence number. Note that the specific fence passed to this function
-	 * should not matter, drivers should only use it to look up the
-	 * corresponding timeline structures.
+	 * sequence number. This should match what @fill_driver_data prints for
+	 * the most recently signalled fence (assuming no delayed signalling).
 	 */
 	void (*timeline_value_str)(struct dma_fence *fence,
 				   char *str, int size);