drm/etnaviv: return GPU fence through the submit structure

The next patch will need the complete dma_fence, instead of just the seqno,
to create the sync_file in etnaviv_ioctl_gem_submit, in case an
out_fence_fd is requested.

The submit needs to hold a reference to the dma_fence, to avoid raceing
with the GPU completing the fence.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
---
New patch in v3.

drivers/gpu/drm/etnaviv/etnaviv_gem.h

@@ -20,6 +20,7 @@
 #include <linux/reservation.h>
 #include "etnaviv_drv.h"
 
+struct dma_fence;
 struct etnaviv_gem_ops;
 struct etnaviv_gem_object;
 
@@ -104,7 +105,7 @@ struct etnaviv_gem_submit {
 	struct drm_device *dev;
 	struct etnaviv_gpu *gpu;
 	struct ww_acquire_ctx ticket;
-	u32 fence;
+	struct dma_fence *fence;
 	unsigned int nr_bos;
 	struct etnaviv_gem_submit_bo bos[0];
 	u32 flags;

drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c

@@ -294,6 +294,7 @@ static void submit_cleanup(struct etnaviv_gem_submit *submit)
 	}
 
 	ww_acquire_fini(&submit->ticket);
+	dma_fence_put(submit->fence);
 	kfree(submit);
 }
 
@@ -435,7 +436,7 @@ int etnaviv_ioctl_gem_submit(struct drm_device *dev, void *data,
 	if (ret == 0)
 		cmdbuf = NULL;
 
-	args->fence = submit->fence;
+	args->fence = submit->fence->seqno;
 
 out:
 	submit_unpin_objects(submit);

drivers/gpu/drm/etnaviv/etnaviv_gpu.c

@@ -1337,8 +1337,8 @@ int etnaviv_gpu_submit(struct etnaviv_gpu *gpu,
 	mutex_lock(&gpu->lock);
 
 	gpu->event[event].fence = fence;
-	submit->fence = fence->seqno;
-	gpu->active_fence = submit->fence;
+	submit->fence = dma_fence_get(fence);
+	gpu->active_fence = submit->fence->seqno;
 
 	if (gpu->lastctx != cmdbuf->ctx) {
 		gpu->mmu->need_flush = true;