drm/nouveau: fence: separate fence alloc and emit

The new (VM_BIND) UAPI exports DMA fences through DRM syncobjs. Hence,
in order to emit fences within DMA fence signalling critical sections
(e.g. as typically done in the DRM GPU schedulers run_job() callback) we
need to separate fence allocation and fence emitting.

Reviewed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230804182406.5222-8-dakr@redhat.com

drivers/gpu/drm/nouveau/dispnv04/crtc.c

@@ -1122,11 +1122,18 @@ nv04_page_flip_emit(struct nouveau_channel *chan,
 	PUSH_NVSQ(push, NV_SW, NV_SW_PAGE_FLIP, 0x00000000);
 	PUSH_KICK(push);
 
-	ret = nouveau_fence_new(chan, false, pfence);
+	ret = nouveau_fence_new(pfence);
 	if (ret)
 		goto fail;
 
+	ret = nouveau_fence_emit(*pfence, chan);
+	if (ret)
+		goto fail_fence_unref;
+
 	return 0;
+
+fail_fence_unref:
+	nouveau_fence_unref(pfence);
 fail:
 	spin_lock_irqsave(&dev->event_lock, flags);
 	list_del(&s->head);

drivers/gpu/drm/nouveau/nouveau_bo.c

@@ -823,29 +823,39 @@ nouveau_bo_move_m2mf(struct ttm_buffer_object *bo, int evict,
 		mutex_lock(&cli->mutex);
 	else
 		mutex_lock_nested(&cli->mutex, SINGLE_DEPTH_NESTING);
+
 	ret = nouveau_fence_sync(nouveau_bo(bo), chan, true, ctx->interruptible);
-	if (ret == 0) {
+	if (ret)
-		ret = drm->ttm.move(chan, bo, bo->resource, new_reg);
+		goto out_unlock;
-		if (ret == 0) {
+
-			ret = nouveau_fence_new(chan, false, &fence);
+	ret = drm->ttm.move(chan, bo, bo->resource, new_reg);
-			if (ret == 0) {
+	if (ret)
-				/* TODO: figure out a better solution here
+		goto out_unlock;
-				 *
+
-				 * wait on the fence here explicitly as going through
+	ret = nouveau_fence_new(&fence);
-				 * ttm_bo_move_accel_cleanup somehow doesn't seem to do it.
+	if (ret)
-				 *
+		goto out_unlock;
-				 * Without this the operation can timeout and we'll fallback to a
+
-				 * software copy, which might take several minutes to finish.
+	ret = nouveau_fence_emit(fence, chan);
-				 */
+	if (ret) {
-				nouveau_fence_wait(fence, false, false);
+		nouveau_fence_unref(&fence);
-				ret = ttm_bo_move_accel_cleanup(bo,
+		goto out_unlock;
-								&fence->base,
-								evict, false,
-								new_reg);
-				nouveau_fence_unref(&fence);
-			}
-		}
 	}
+
+	/* TODO: figure out a better solution here
+	 *
+	 * wait on the fence here explicitly as going through
+	 * ttm_bo_move_accel_cleanup somehow doesn't seem to do it.
+	 *
+	 * Without this the operation can timeout and we'll fallback to a
+	 * software copy, which might take several minutes to finish.
+	 */
+	nouveau_fence_wait(fence, false, false);
+	ret = ttm_bo_move_accel_cleanup(bo, &fence->base, evict, false,
+					new_reg);
+	nouveau_fence_unref(&fence);
+
+out_unlock:
 	mutex_unlock(&cli->mutex);
 	return ret;
 }

drivers/gpu/drm/nouveau/nouveau_chan.c

@@ -62,9 +62,11 @@ nouveau_channel_idle(struct nouveau_channel *chan)
 		struct nouveau_fence *fence = NULL;
 		int ret;
 
-		ret = nouveau_fence_new(chan, false, &fence);
+		ret = nouveau_fence_new(&fence);
 		if (!ret) {
-			ret = nouveau_fence_wait(fence, false, false);
+			ret = nouveau_fence_emit(fence, chan);
+			if (!ret)
+				ret = nouveau_fence_wait(fence, false, false);
 			nouveau_fence_unref(&fence);
 		}
 

drivers/gpu/drm/nouveau/nouveau_dmem.c

@@ -209,7 +209,8 @@ static vm_fault_t nouveau_dmem_migrate_to_ram(struct vm_fault *vmf)
 		goto done;
 	}
 
-	nouveau_fence_new(dmem->migrate.chan, false, &fence);
+	if (!nouveau_fence_new(&fence))
+		nouveau_fence_emit(fence, dmem->migrate.chan);
 	migrate_vma_pages(&args);
 	nouveau_dmem_fence_done(&fence);
 	dma_unmap_page(drm->dev->dev, dma_addr, PAGE_SIZE, DMA_BIDIRECTIONAL);
@@ -402,7 +403,8 @@ nouveau_dmem_evict_chunk(struct nouveau_dmem_chunk *chunk)
 		}
 	}
 
-	nouveau_fence_new(chunk->drm->dmem->migrate.chan, false, &fence);
+	if (!nouveau_fence_new(&fence))
+		nouveau_fence_emit(fence, chunk->drm->dmem->migrate.chan);
 	migrate_device_pages(src_pfns, dst_pfns, npages);
 	nouveau_dmem_fence_done(&fence);
 	migrate_device_finalize(src_pfns, dst_pfns, npages);
@@ -675,7 +677,8 @@ static void nouveau_dmem_migrate_chunk(struct nouveau_drm *drm,
 		addr += PAGE_SIZE;
 	}
 
-	nouveau_fence_new(drm->dmem->migrate.chan, false, &fence);
+	if (!nouveau_fence_new(&fence))
+		nouveau_fence_emit(fence, chunk->drm->dmem->migrate.chan);
 	migrate_vma_pages(args);
 	nouveau_dmem_fence_done(&fence);
 	nouveau_pfns_map(svmm, args->vma->vm_mm, args->start, pfns, i);

drivers/gpu/drm/nouveau/nouveau_fence.c

@@ -210,6 +210,9 @@ nouveau_fence_emit(struct nouveau_fence *fence, struct nouveau_channel *chan)
 	struct nouveau_fence_priv *priv = (void*)chan->drm->fence;
 	int ret;
 
+	if (unlikely(!chan->fence))
+		return -ENODEV;
+
 	fence->channel  = chan;
 	fence->timeout  = jiffies + (15 * HZ);
 
@@ -396,25 +399,16 @@ nouveau_fence_unref(struct nouveau_fence **pfence)
 }
 
 int
-nouveau_fence_new(struct nouveau_channel *chan, bool sysmem,
+nouveau_fence_new(struct nouveau_fence **pfence)
-		  struct nouveau_fence **pfence)
 {
 	struct nouveau_fence *fence;
-	int ret = 0;
-
-	if (unlikely(!chan->fence))
-		return -ENODEV;
 
 	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
 	if (!fence)
 		return -ENOMEM;
 
-	ret = nouveau_fence_emit(fence, chan);
-	if (ret)
-		nouveau_fence_unref(&fence);
-
 	*pfence = fence;
-	return ret;
+	return 0;
 }
 
 static const char *nouveau_fence_get_get_driver_name(struct dma_fence *fence)

drivers/gpu/drm/nouveau/nouveau_fence.h

@@ -17,8 +17,7 @@ struct nouveau_fence {
 	unsigned long timeout;
 };
 
-int  nouveau_fence_new(struct nouveau_channel *, bool sysmem,
+int  nouveau_fence_new(struct nouveau_fence **);
-		       struct nouveau_fence **);
 void nouveau_fence_unref(struct nouveau_fence **);
 
 int  nouveau_fence_emit(struct nouveau_fence *, struct nouveau_channel *);

drivers/gpu/drm/nouveau/nouveau_gem.c

@@ -873,8 +873,11 @@ revalidate:
 		}
 	}
 
-	ret = nouveau_fence_new(chan, false, &fence);
+	ret = nouveau_fence_new(&fence);
+	if (!ret)
+		ret = nouveau_fence_emit(fence, chan);
 	if (ret) {
+		nouveau_fence_unref(&fence);
 		NV_PRINTK(err, cli, "error fencing pushbuf: %d\n", ret);
 		WIND_RING(chan);
 		goto out;