drm/msm/a6xx: Handle GMU prepare-slumber hfi failure

When prepare-slumber hfi fails, we should follow a6xx_gmu_force_off()
sequence.
Signed-off-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/498401/
Link: https://lore.kernel.org/r/20220819015030.v5.7.I54815c7c36b80d4725cd054e536365250454452f@changeidSigned-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/adreno/a6xx_gmu.c

@@ -1086,7 +1086,11 @@ static void a6xx_gmu_shutdown(struct a6xx_gmu *gmu)
 		a6xx_bus_clear_pending_transactions(adreno_gpu);
 
 		/* tell the GMU we want to slumber */
-		a6xx_gmu_notify_slumber(gmu);
+		ret = a6xx_gmu_notify_slumber(gmu);
+		if (ret) {
+			a6xx_gmu_force_off(gmu);
+			return;
+		}
 
 		ret = gmu_poll_timeout(gmu,
 			REG_A6XX_GPU_GMU_AO_GPU_CX_BUSY_STATUS, val,