rtio: optimize flag handling

soc/artiqlib/rtio/core.py

@@ -297,17 +297,15 @@ class RTIO(Module, AutoCSR):
 
         self._r_o_timestamp = CSRStorage(counter_width + fine_ts_width)
         self._r_o_value = CSRStorage(2)
-        self._r_o_writable = CSRStatus()
         self._r_o_we = CSR()
         self._r_o_replace = CSR()
-        self._r_o_underflow = CSRStatus()
+        self._r_o_status = CSRStatus(2)
         self._r_o_underflow_reset = CSR()
 
         self._r_i_timestamp = CSRStatus(counter_width + fine_ts_width)
         self._r_i_value = CSRStatus()
-        self._r_i_readable = CSRStatus()
         self._r_i_re = CSR()
-        self._r_i_overflow = CSRStatus()
+        self._r_i_status = CSRStatus(2)
         self._r_i_overflow_reset = CSR()
         self._r_i_pileup_count = CSRStatus(16)
         self._r_i_pileup_reset = CSR()
@@ -351,10 +349,9 @@ class RTIO(Module, AutoCSR):
             self.bank_o.sel.eq(self._r_chan_sel.storage),
             self.bank_o.timestamp.eq(self._r_o_timestamp.storage),
             self.bank_o.value.eq(self._r_o_value.storage),
-            self._r_o_writable.status.eq(self.bank_o.writable),
             self.bank_o.we.eq(self._r_o_we.re),
             self.bank_o.replace.eq(self._r_o_replace.re),
-            self._r_o_underflow.status.eq(self.bank_o.underflow),
+            self._r_o_status.status.eq(Cat(~self.bank_o.writable, self.bank_o.underflow)),
             self.bank_o.underflow_reset.eq(self._r_o_underflow_reset.re)
         ]
 
@@ -363,9 +360,8 @@ class RTIO(Module, AutoCSR):
             self.bank_i.sel.eq(self._r_chan_sel.storage),
             self._r_i_timestamp.status.eq(self.bank_i.timestamp),
             self._r_i_value.status.eq(self.bank_i.value),
-            self._r_i_readable.status.eq(self.bank_i.readable),
             self.bank_i.re.eq(self._r_i_re.re),
-            self._r_i_overflow.status.eq(self.bank_i.overflow),
+            self._r_i_status.status.eq(Cat(~self.bank_i.readable, self.bank_i.overflow)),
             self.bank_i.overflow_reset.eq(self._r_i_overflow_reset.re),
             self._r_i_pileup_count.status.eq(self.bank_i.pileup_count),
             self.bank_i.pileup_reset.eq(self._r_i_pileup_reset.re)

soc/runtime/rtio.c

@@ -3,6 +3,11 @@
 #include "exceptions.h"
 #include "rtio.h"
 
+#define RTIO_O_STATUS_FULL 1
+#define RTIO_O_STATUS_UNDERFLOW 2
+#define RTIO_I_STATUS_EMPTY 1
+#define RTIO_I_STATUS_OVERFLOW 2
+
 long long int previous_fud_end_time;
 
 void rtio_init(void)
@@ -20,16 +25,22 @@ void rtio_oe(int channel, int oe)
 
 void rtio_set(long long int timestamp, int channel, int value)
 {
+    int status;
+
     rtio_chan_sel_write(channel);
     rtio_o_timestamp_write(timestamp);
     rtio_o_value_write(value);
-    while(!rtio_o_writable_read());
     rtio_o_we_write(1);
-    if(rtio_o_underflow_read()) {
+    status = rtio_o_status_read();
+    if(status) {
+        if(status & RTIO_O_STATUS_FULL)
+            while(rtio_o_status_read() & RTIO_O_STATUS_FULL);
+        if(status & RTIO_O_STATUS_UNDERFLOW) {
             rtio_o_underflow_reset_write(1);
             exception_raise(EID_RTIO_UNDERFLOW);
         }
     }
+}
 
 void rtio_replace(long long int timestamp, int channel, int value)
 {
@@ -37,7 +48,7 @@ void rtio_replace(long long int timestamp, int channel, int value)
     rtio_o_timestamp_write(timestamp);
     rtio_o_value_write(value);
     rtio_o_replace_write(1);
-    if(rtio_o_underflow_read()) {
+    if(rtio_o_status_read() & RTIO_O_STATUS_UNDERFLOW) {
         rtio_o_underflow_reset_write(1);
         exception_raise(EID_RTIO_UNDERFLOW);
     }
@@ -52,21 +63,27 @@ long long int rtio_get_counter(void)
 long long int rtio_get(int channel, long long int time_limit)
 {
     long long int r;
+    int status;
 
     rtio_chan_sel_write(channel);
-    while(rtio_i_readable_read() || (rtio_get_counter() < time_limit)) {
+    while(status = rtio_i_status_read()) {
-        if(rtio_i_overflow_read()) {
+        if(rtio_i_status_read() & RTIO_I_STATUS_OVERFLOW) {
             rtio_i_overflow_reset_write(1);
             exception_raise(EID_RTIO_OVERFLOW);
         }
-        if(rtio_i_readable_read()) {
+        if(rtio_get_counter() >= time_limit) {
+            /* 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)
+                return -1;
+        }
+        /* input FIFO is empty - keep waiting */
+    }
     r = rtio_i_timestamp_read();
     rtio_i_re_write(1);
     return r;
 }
-    }
-    return -1;
-}
 
 int rtio_pileup_count(int channel)
 {
@@ -101,7 +118,7 @@ void rtio_fud(long long int fud_time)
     rtio_o_timestamp_write(fud_end_time);
     rtio_o_value_write(0);
     rtio_o_we_write(1);
-    if(rtio_o_underflow_read()) {
+    if(rtio_o_status_read() & RTIO_O_STATUS_UNDERFLOW) {
         rtio_o_underflow_reset_write(1);
         exception_raise(EID_RTIO_UNDERFLOW);
     }