runtime/rtio: fix rtio_input_wait(), add RTIOTimeout

artiq/coredevice/__init__.py

@@ -1,12 +1,13 @@
-from artiq.coredevice import exceptions, dds
+from artiq.coredevice import exceptions, dds, spi
 from artiq.coredevice.exceptions import (RTIOUnderflow, RTIOSequenceError,
                                          RTIOCollisionError, RTIOOverflow,
-                                         DDSBatchError, CacheError)
+                                         DDSBatchError, CacheError,
+                                         RTIOTimeout)
 from artiq.coredevice.dds import (PHASE_MODE_CONTINUOUS, PHASE_MODE_ABSOLUTE,
                                   PHASE_MODE_TRACKING)
 
 __all__ = []
 __all__ += ["RTIOUnderflow", "RTIOSequenceError", "RTIOCollisionError",
-            "RTIOOverflow", "DDSBatchError", "CacheError"]
+            "RTIOOverflow", "DDSBatchError", "CacheError", "RTIOTimeout"]
 __all__ += ["PHASE_MODE_CONTINUOUS", "PHASE_MODE_ABSOLUTE",
             "PHASE_MODE_TRACKING"]

artiq/coredevice/exceptions.py

@@ -108,6 +108,17 @@ class RTIOOverflow(Exception):
     """
     artiq_builtin = True
 
+class RTIOTimeout(Exception):
+    """Raised when an RTIO input operation does not complete within the expected
+    time. This is only raised by channels where a response is guaranteed, such
+    as RT2WB (DDS and SPI).
+
+    This does not interrupt operations further than cancelling the current read
+    attempt. Reading can be reattempted after the exception is caught, and
+    events that have arrived in the meantime will be retrieved.
+    """
+    artiq_builtin = True
+
 class DDSBatchError(Exception):
     """Raised when attempting to start a DDS batch while already in a batch,
     or when too many commands are batched.

artiq/runtime/rt2wb.c

@@ -16,8 +16,20 @@ unsigned int rt2wb_read_sync(long long int timestamp, int channel, int addr,
         int duration)
 {
     unsigned int data;
+    int status;
+
     rtio_output(timestamp, channel, addr, 0);
-    rtio_input_wait(timestamp + duration, channel);
+
+    status = rtio_input_wait(timestamp + duration, channel);
+    if (status & RTIO_I_STATUS_OVERFLOW)
+        artiq_raise_from_c("RTIOOverflow",
+                "RT2WB read overflow on channel {0}",
+                channel, 0, 0);
+    if (status & RTIO_I_STATUS_EMPTY)
+        artiq_raise_from_c("RTIOTimeout",
+                "RT2WB read timeout on channel {0}",
+                channel, 0, 0);
+
     data = rtio_i_data_read();
     rtio_i_re_write(1);
     return data;

artiq/runtime/rtio.c

@@ -51,7 +51,7 @@ void rtio_output(long long int timestamp, int channel, unsigned int addr,
 }
 
 
-void rtio_input_wait(long long int timeout, int channel)
+int rtio_input_wait(long long int timeout, int channel)
 {
     int status;
 
@@ -59,21 +59,19 @@ void rtio_input_wait(long long int timeout, int channel)
     while((status = rtio_i_status_read())) {
         if(status & RTIO_I_STATUS_OVERFLOW) {
             rtio_i_overflow_reset_write(1);
-            artiq_raise_from_c("RTIOOverflow",
-                "RTIO input overflow on channel {0}",
-                channel, 0, 0);
+            break;
         }
         if(rtio_get_counter() >= timeout) {
             /* check empty flag again to prevent race condition.
              * now we are sure that the time limit has been exceeded.
              */
-            if(rtio_i_status_read() & RTIO_I_STATUS_EMPTY)
-                artiq_raise_from_c("InternalError",
-                        "RTIO input timeout on channel {0}",
-                        channel, 0, 0);
+            status = rtio_i_status_read();
+            if(status & RTIO_I_STATUS_EMPTY)
+                break;
         }
         /* input FIFO is empty - keep waiting */
     }
+    return status;
 }
 
 

artiq/runtime/rtio.h

@@ -19,7 +19,7 @@ void rtio_log(long long int timestamp, const char *format, ...);
 void rtio_log_va(long long int timestamp, const char *format, va_list args);
 void rtio_output(long long int timestamp, int channel, unsigned int address,
         unsigned int data);
-void rtio_input_wait(long long int timeout, int channel);
+int rtio_input_wait(long long int timeout, int channel);
 
 static inline void rtio_write_and_process_status(long long int timestamp, int channel)
 {

artiq/runtime/ttl.c

@@ -22,8 +22,15 @@ void ttl_set_sensitivity(long long int timestamp, int channel, int sensitivity)
 long long int ttl_get(int channel, long long int time_limit)
 {
     long long int r;
+    int status = rtio_input_wait(time_limit, channel);
+
+    if (status & RTIO_I_STATUS_OVERFLOW)
+        artiq_raise_from_c("RTIOOverflow",
+                "RTIO input overflow on channel {0}",
+                channel, 0, 0);
+    if (status & RTIO_I_STATUS_EMPTY)
+        return -1;
 
-    rtio_input_wait(time_limit, channel);
     r = rtio_i_timestamp_read();
     rtio_i_re_write(1);
     return r;