[avr-gcc-list] [PATCH] avarice: debugWire: JTAG ICE: Cannot synchonise

[Shaun Jackman]

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  <address@hidden>

        * 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)

avarice-dw.diff
Description: Text document