comm_serial: allow to use dynamic baudrate

artiq/coredevice/comm_serial.py

@@ -22,6 +22,7 @@ class _H2DMsgType(Enum):
     REQUEST_IDENT = 1
     LOAD_OBJECT = 2
     RUN_KERNEL = 3
+    UART_SET_BDRATE = 4
 
 
 class _D2HMsgType(Enum):
@@ -58,6 +59,34 @@ class Comm:
     def __init__(self, dev="/dev/ttyUSB1", baud=115200):
         self._fd = os.open(dev, os.O_RDWR | os.O_NOCTTY)
         self.port = os.fdopen(self._fd, "r+b", buffering=0)
+        self.dev = dev
+        real_baud = baud
+        baud = 115200
+        self.set_baud(baud)
+        if real_baud != baud:
+            baud = real_baud
+            self.set_remote_baud(baud)
+            self.set_baud(baud)
+        self.current_baud = baud
+
+    def set_remote_baud(self, baud):
+            clk_freq = 80000000
+            _write_exactly(self.port, struct.pack(
+                ">lbl", 0x5a5a5a5a, _H2DMsgType.UART_SET_BDRATE.value,
+                int((baud/clk_freq)*2**32)))
+            handshake = 0
+            while handshake < 4:
+                recv = struct.unpack(
+                    "B", _read_exactly(self.port, 1))
+                if recv[0] == 0x5a:
+                    handshake += 1
+                else:
+                    logger.debug("SYNC ERR {:02x}\n".format(int(recv[0])))
+                    handshake = 0
+            self.set_baud(baud)
+            logger.debug("Synchronized")
+
+    def set_baud(self, baud):
         iflag, oflag, cflag, lflag, ispeed, ospeed, cc = \
             termios.tcgetattr(self._fd)
         iflag = termios.IGNBRK | termios.IGNPAR
@@ -72,9 +101,12 @@ class Comm:
         termios.tcdrain(self._fd)
         termios.tcflush(self._fd, termios.TCOFLUSH)
         termios.tcflush(self._fd, termios.TCIFLUSH)
-        logger.debug("connected to {} at {} baud".format(dev, baud))
+        logger.debug("connected to {} at {} baud".format(self.dev, baud))
 
     def close(self):
+        if self.current_baud != 115200:
+            self.set_remote_baud(115200)
+            self.set_baud(115200)
         self.port.close()
 
     def __enter__(self):

soc/runtime/comm_serial.c

@@ -10,6 +10,7 @@ enum {
     MSGTYPE_REQUEST_IDENT = 1,
     MSGTYPE_LOAD_OBJECT,
     MSGTYPE_RUN_KERNEL,
+    MSGTYPE_UART_SETBDRATE,
 };
 
 /* device to host */
@@ -161,7 +162,12 @@ void comm_serve(object_loader load_object, kernel_runner run_kernel)
             receive_and_load_object(load_object);
         else if(msgtype == MSGTYPE_RUN_KERNEL)
             receive_and_run_kernel(run_kernel);
-        else
+        else if(msgtype == MSGTYPE_UART_SETBDRATE) {
+            unsigned int ftw = receive_int();
+            send_int(0x5a5a5a5a);
+            uart_sync();
+            uart_tuning_word_write(ftw);
+        } else
             send_char(MSGTYPE_MESSAGE_UNRECOGNIZED);
     }
 }