drm/etnaviv: consider completed fence seqno in hang check

Some GPU heavy test programs manage to trigger the hangcheck quite often.
If there are no other GPU users in the system and the test program
exhibits a very regular structure in the commandstreams that are being
submitted, we can end up with two distinct submits managing to trigger
the hangcheck with the FE in a very similar address range. This leads
the hangcheck to believe that the GPU is stuck, while in reality the GPU
is already busy working on a different job. To avoid those spurious
GPU resets, also remember and consider the last completed fence seqno
in the hang check.
Reported-by: Joerg Albert <joerg.albert@iav.de>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>

drivers/gpu/drm/etnaviv/etnaviv_gpu.h

@@ -130,6 +130,7 @@ struct etnaviv_gpu {
 
 	/* hang detection */
 	u32 hangcheck_dma_addr;
+	u32 hangcheck_fence;
 
 	void __iomem *mmio;
 	int irq;

drivers/gpu/drm/etnaviv/etnaviv_sched.c

@@ -107,8 +107,10 @@ static enum drm_gpu_sched_stat etnaviv_sched_timedout_job(struct drm_sched_job
 	 */
 	dma_addr = gpu_read(gpu, VIVS_FE_DMA_ADDRESS);
 	change = dma_addr - gpu->hangcheck_dma_addr;
-	if (change < 0 || change > 16) {
+	if (gpu->completed_fence != gpu->hangcheck_fence ||
+	    change < 0 || change > 16) {
 		gpu->hangcheck_dma_addr = dma_addr;
+		gpu->hangcheck_fence = gpu->completed_fence;
 		goto out_no_timeout;
 	}