From 76fed11d59fcbed4376a7ad3aa8e58ea96d4366d Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Tue, 30 Sep 2014 19:32:11 +0800
Subject: [PATCH] rtio: raise RTIOSequenceError exceptions when events are not
 submitted in-order

---
 artiq/devices/rtio_core.py          |  3 +++
 artiq/devices/runtime_exceptions.py | 15 +++++++++++++++
 doc/manual/drivers_reference.rst    |  6 ++++++
 soc/runtime/dds.c                   |  6 ++++++
 soc/runtime/exceptions.h            |  3 ++-
 test/full_stack.py                  | 21 +++++++++++++++++++++
 6 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/artiq/devices/rtio_core.py b/artiq/devices/rtio_core.py
index 2eedbd279..88143a919 100644
--- a/artiq/devices/rtio_core.py
+++ b/artiq/devices/rtio_core.py
@@ -1,4 +1,5 @@
 from artiq.language.core import *
+from artiq.devices.runtime_exceptions import RTIOSequenceError
 
 
 class _RTIOBase(AutoContext):
@@ -16,6 +17,8 @@ class _RTIOBase(AutoContext):
 
     @kernel
     def _set_value(self, value):
+        if now() < self.previous_timestamp:
+            raise RTIOSequenceError
         if self.previous_value != value:
             if self.previous_timestamp == now():
                 syscall("rtio_replace", now(), self.channel, value)
diff --git a/artiq/devices/runtime_exceptions.py b/artiq/devices/runtime_exceptions.py
index c9a90b697..fe3521470 100644
--- a/artiq/devices/runtime_exceptions.py
+++ b/artiq/devices/runtime_exceptions.py
@@ -6,13 +6,28 @@ from artiq.language.core import RuntimeException
 # Must be kept in sync with soc/runtime/exceptions.h
 
 class OutOfMemory(RuntimeException):
+    """Raised when the runtime fails to allocate memory.
+
+    """
     eid = 0
 
 
 class RTIOUnderflow(RuntimeException):
+    """Raised when the CPU fails to submit a RTIO event early enough (with respect to the event's timestamp).
+
+    """
     eid = 1
 
 
+# Raised by RTIO driver for regular RTIO.
+# Raised by runtime for DDS FUD.
+class RTIOSequenceError(RuntimeException):
+    """Raised when an event was not submitted with an increasing timestamp.
+
+    """
+    eid = 2
+
+
 exception_map = {e.eid: e for e in globals().values()
                  if inspect.isclass(e)
                  and issubclass(e, RuntimeException)
diff --git a/doc/manual/drivers_reference.rst b/doc/manual/drivers_reference.rst
index 60378625f..7bc405325 100644
--- a/doc/manual/drivers_reference.rst
+++ b/doc/manual/drivers_reference.rst
@@ -12,3 +12,9 @@ Drivers reference
 
 .. automodule:: artiq.devices.dds_core
     :members:
+
+:mod:`artiq.devices.runtime_exceptions` module
+----------------------------------------------
+
+.. automodule:: artiq.devices.runtime_exceptions
+    :members:
diff --git a/soc/runtime/dds.c b/soc/runtime/dds.c
index ae9bcab57..d34c5d308 100644
--- a/soc/runtime/dds.c
+++ b/soc/runtime/dds.c
@@ -28,8 +28,11 @@ static void fud_sync(void)
 static void fud(long long int fud_time)
 {
     int r;
+    static int previous_fud_time;
 
     r = rtio_reset_read();
+    if(r)
+        previous_fud_time = 0;
     rtio_reset_write(0);
 
     rtio_chan_sel_write(RTIO_FUD_CHANNEL);
@@ -37,6 +40,9 @@ static void fud(long long int fud_time)
         rtio_counter_update_write(1);
         fud_time = rtio_counter_read() + 3000;
     }
+    if(fud_time < previous_fud_time)
+        exception_raise(EID_RTIO_SEQUENCE_ERROR);
+
     rtio_o_timestamp_write(fud_time);
     rtio_o_value_write(1);
     rtio_o_we_write(1);
diff --git a/soc/runtime/exceptions.h b/soc/runtime/exceptions.h
index d701153b0..bc53ea487 100644
--- a/soc/runtime/exceptions.h
+++ b/soc/runtime/exceptions.h
@@ -3,7 +3,8 @@
 
 enum {
 	EID_OUT_OF_MEMORY = 0,
-	EID_RTIO_UNDERFLOW = 1
+	EID_RTIO_UNDERFLOW = 1,
+	EID_RTIO_SEQUENCE_ERROR = 2
 };
 
 int exception_setjmp(void *jb) __attribute__((returns_twice));
diff --git a/test/full_stack.py b/test/full_stack.py
index 58c8cf40f..0356e93ef 100644
--- a/test/full_stack.py
+++ b/test/full_stack.py
@@ -163,6 +163,17 @@ class _RTIOUnderflow(AutoContext):
             self.o.pulse(25*ns)
 
 
+class _RTIOSequenceError(AutoContext):
+    parameters = "o"
+
+    @kernel
+    def run(self):
+        t = now()
+        self.o.pulse(25*us)
+        at(t)
+        self.o.pulse(25*us)
+
+
 class RTIOCase(unittest.TestCase):
     def test_loopback(self):
         npulses = 4
@@ -186,3 +197,13 @@ class RTIOCase(unittest.TestCase):
             )
             with self.assertRaises(runtime_exceptions.RTIOUnderflow):
                 uut.run()
+
+    def test_sequence_error(self):
+        with corecom_serial.CoreCom() as com:
+            coredev = core.Core(com)
+            uut = _RTIOSequenceError(
+                core=coredev,
+                o=rtio_core.RTIOOut(core=coredev, channel=1)
+            )
+            with self.assertRaises(runtime_exceptions.RTIOSequenceError):
+                uut.run()