[PATCH] drm/etnaviv: fix GPU vs sync point race

[Lucas Stach]

If the FE is restarted before the sync point event is cleared, the GPU
might trigger a completion IRQ for the next sync point before corrupting
the state of the currently running worker.

Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
---
 drivers/gpu/drm/etnaviv/etnaviv_gpu.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
index 93a103eb1083..8ff5d01e776d 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
@@ -1484,22 +1484,18 @@ int etnaviv_gpu_submit(struct etnaviv_gpu *gpu,
 	return ret;
 }
 
-static void etnaviv_process_sync_point(struct etnaviv_gpu *gpu,
-	struct etnaviv_event *event)
-{
-	u32 addr = gpu_read(gpu, VIVS_FE_DMA_ADDRESS);
-
-	event->sync_point(gpu, event);
-	etnaviv_gpu_start_fe(gpu, addr + 2, 2);
-}
-
 static void sync_point_worker(struct work_struct *work)
 {
 	struct etnaviv_gpu *gpu = container_of(work, struct etnaviv_gpu,
 					       sync_point_work);
+	struct etnaviv_event *event = &gpu->event[gpu->sync_point_event];
+	u32 addr = gpu_read(gpu, VIVS_FE_DMA_ADDRESS);
 
-	etnaviv_process_sync_point(gpu, &gpu->event[gpu->sync_point_event]);
+	event->sync_point(gpu, event);
 	event_free(gpu, gpu->sync_point_event);
+
+	/* restart FE last to avoid GPU and IRQ racing against this worker */
+	etnaviv_gpu_start_fe(gpu, addr + 2, 2);
 }
 
 /*
-- 
2.11.0