test_spi: drain errors and be more strict on where we expect errors

artiq/test/coredevice/test_spi.py

@@ -2,6 +2,10 @@ from artiq.experiment import *
 from artiq.test.hardware_testbench import ExperimentCase
 
 
+class WrongError(Exception):
+    pass
+
+
 class Collision(EnvExperiment):
     def build(self):
         self.setattr_device("core")
@@ -11,7 +15,10 @@ class Collision(EnvExperiment):
     def run(self):
         self.core.break_realtime()
         t = now_mu()
-        self.spi0.set_config_mu()
+        try:
+            self.spi0.set_config_mu()
+        except RTIOBusy:
+            raise WrongError()
         at_mu(t)
         self.spi0.set_config_mu()
 
@@ -24,18 +31,49 @@ class Busy(EnvExperiment):
 
     @kernel
     def run(self):
-        self.core.break_realtime()
-        t = now_mu()
-        self.spi0.set_config_mu()
-        at_mu(t + self.spi0.ref_period_mu)
-        self.spi0.set_config_mu()  # causes the error
-        self.led.on()
-        self.led.sync()            # registers the error
-        self.core.break_realtime()
+        try:
+            self.core.break_realtime()
+            self.spi0.set_config_mu()
+            t = now_mu()
+            self.spi0.set_config_mu()
+            at_mu(t + self.spi0.ref_period_mu)
+            self.spi0.set_config_mu()  # causes the error
+            self.led.on()
+            self.led.sync()            # registers the error
+            self.core.break_realtime()
+        except RTIOBusy:
+            raise WrongError()         # we don't expect RTIOBusy so far
         self.spi0.set_config_mu()  # raises the error
 
 
+class DrainErrors(EnvExperiment):
+    def build(self):
+        self.setattr_device("core")
+        self.setattr_device("spi0")
+        self.setattr_device("led")
+
+    @kernel
+    def run(self):
+        while True:
+            try:
+                self.core.break_realtime()
+                delay(100*us)
+                self.spi0.set_config_mu()
+                self.led.on()
+                self.led.sync()
+                self.core.break_realtime()
+                self.spi0.set_config_mu()
+                self.led.off()
+                return
+            except:
+                pass
+
+
 class SPITest(ExperimentCase):
+    def tearDown(self):
+        self.execute(DrainErrors)
+        ExperimentCase.tearDown(self)
+
     def test_collision(self):
         with self.assertRaises(RTIOCollision):
             self.execute(Collision)