nvif_chan_gpfifo_wait
int nvif_chan_gpfifo_wait(struct nvif_chan *, u32 gpfifo_nr, u32 push_nr);
ret = nvif_chan_gpfifo_wait(&chan->chan, exec_job->push.count + 1, 16);
ret = nvif_chan_gpfifo_wait(&chan->chan, req->nr_push + 1, 16);
return nvif_chan_gpfifo_wait(chan, 1, push_nr);