faft-cr50: check /dev/tpm0 during reboot stress am: 168f20a0cc am: bcaa8f0611 am: 898314a34c am: a7141df252

Original change: undetermined

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I96283d981ca0052fb96e10fbe840b6984d653516
diff --git a/server/site_tests/firmware_Cr50DeepSleepStress/firmware_Cr50DeepSleepStress.py b/server/site_tests/firmware_Cr50DeepSleepStress/firmware_Cr50DeepSleepStress.py
index 0dc11ca..4090395 100644
--- a/server/site_tests/firmware_Cr50DeepSleepStress/firmware_Cr50DeepSleepStress.py
+++ b/server/site_tests/firmware_Cr50DeepSleepStress/firmware_Cr50DeepSleepStress.py
@@ -113,8 +113,13 @@
         errors = []
 
         for i in range(suspend_count):
+            if not self._dut_is_responsive():
+                raise error.TestFail('Unable to ssh into DUT after %d resets' %
+                                     i)
+            self.host.run('ls /dev/tpm0')
             # Power off the device
-            self.host.power_off_via_servo()
+            self.set_ap_off_power_mode('shutdown')
+
             time.sleep(self.MIN_SUSPEND)
 
             # Power on the device