[AVaRICE-user] [PATCH] avarice: debugWire: JTAG ICE: Cannot synchonise

[Shaun J. <sja...@gm...>]

This bug is caused by using debugWire. It manifests itself using both the
JTAG ICE mkII and the AVR Dragon.

The attached patch fixes a clear bug in jtag2bp.cc.

The JTAG ICE mkII and Dragon do not respond correctly to the CMND_RESET
command while in debugWire mode. The command always times out the
first time sending it. When resending the command, sometimes the
debugger will ack (RSP_OK) the command, sometimes it will repeatedly
send EVT_BREAK responses instead, never acking the CMND_RESET command.
I opted to send CMND_FORCED_STOP and CMND_WRITE_PC(0) when using
debugWire instead of CMND_RESET. This solution seems to work, although
other equally valid solutions surely exist.

I'm able to debug using avarice with GDB and an AVR Dragon and
debugWire now! I haven't yet tested breakpoints...

Cheers,
Shaun

2007-07-08  Shaun Jackman  <sja...@gm...>

	* src/jtag2bp.cc (layoutBreakpoints) <useDebugWire>: Bug fix.
	GDB continue command would hang when using debugWire.
	* src/jtag2io.cc (recvFrame): Correctly report a timeout.
	* src/jtag2run.cc (resetProgram): The JTAG ICE mkII and Dragon
	do not respond correctly to the CMND_RESET command while in
	debugWire mode. Send CMND_FORCED_STOP and CMND_WRITE_PC(0)
	instead.

Index: src/jtag2bp.cc
===================================================================
RCS file: /cvsroot/avarice/avarice/src/jtag2bp.cc,v
retrieving revision 1.7
diff -u -p -r1.7 jtag2bp.cc
--- src/jtag2bp.cc	21 Feb 2007 20:57:47 -0000	1.7
+++ src/jtag2bp.cc	8 Jul 2007 16:50:54 -0000
@@ -401,7 +401,7 @@ bool jtag2::layoutBreakpoints(void)
     if (useDebugWire)
       {
 	  int k;
-	  while (k < (MAX_BREAKPOINTS2 + 1))
+	  for (k = 1; k < MAX_BREAKPOINTS2 + 1; k++)
             {
 		remaining_bps[k] = false;
             }
Index: src/jtag2io.cc
===================================================================
RCS file: /cvsroot/avarice/avarice/src/jtag2io.cc,v
retrieving revision 1.11
diff -u -p -r1.11 jtag2io.cc
--- src/jtag2io.cc	17 Feb 2007 22:41:46 -0000	1.11
+++ src/jtag2io.cc	8 Jul 2007 16:50:54 -0000
@@ -141,10 +141,12 @@ int jtag2::recvFrame(unsigned char *&msg
 		break;
 	} else {
 	    rv = timeout_read(&c, 1, JTAG_RESPONSE_TIMEOUT);
-	    debugOut("recv: 0x%02x\n", c);
-	    if (rv == 0)
+	    if (rv == 0) {
 		/* timeout */
+		debugOut("recv: timeout\n");
 		break;
+	    }
+	    debugOut("recv: 0x%02x\n", c);
 	}
 	checksum ^= c;

Index: src/jtag2run.cc
===================================================================
RCS file: /cvsroot/avarice/avarice/src/jtag2run.cc,v
retrieving revision 1.7
diff -u -p -r1.7 jtag2run.cc
--- src/jtag2run.cc	17 Feb 2007 22:41:46 -0000	1.7
+++ src/jtag2run.cc	8 Jul 2007 16:50:54 -0000
@@ -74,14 +74,21 @@ bool jtag2::setProgramCounter(unsigned l

  bool jtag2::resetProgram(void)
 {
-    uchar cmd[2] = { CMND_RESET, 0x01 };
-    uchar *resp;
-    int respSize;
+    if (useDebugWire) {
+	/* The JTAG ICE mkII and Dragon do not respond correctly to
+	 * the CMND_RESET command while in debugWire mode. */
+	return interruptProgram()
+	    && setProgramCounter(0);
+    } else {
+	uchar cmd[2] = { CMND_RESET, 0x01 };
+	uchar *resp;
+	int respSize;

-    bool rv = doJtagCommand(cmd, 2, resp, respSize);
-    delete [] resp;
+	bool rv = doJtagCommand(cmd, 2, resp, respSize);
+	delete [] resp;

-    return rv;
+	return rv;
+    }
 }

  bool jtag2::interruptProgram(void)