Something strikes me as pretty broken here. Maybe I am seeing ghosts.
I put in a few prints to see what was going on, then got confused and
ran from the debugger. This is what I found:
static int jlink_get_version_info(void)
{
int result;
int len;
u32 jlink_caps, jlink_max_size;
/* query hardware version */
jlink_simple_command(EMU_CMD_VERSION);
result = jlink_usb_read(jlink_jtag_handle, 2);
if (2 != result)
{
///***** Sometimes this fails, that doesn't seem to matter
LOG_ERROR("J-Link command EMU_CMD_VERSION failed
(%d)\n", result);
return ERROR_JTAG_DEVICE_ERROR;
}
///***** most of the time it works and we get to here
///***** Problem is that what is read is "J-" the first two bytes of
the jlink identifier string
len = buf_get_u32(usb_in_buffer, 0, 16);
///***** len now holds 11594, which is what buf_get_u32 returns when
it is fed "J-"
result = jlink_usb_read(jlink_jtag_handle, len);
///***** jlink_usb_read doesn't check the length of the buffer before reading
///***** so it wipes out a bunch of variables including jlink_jtag_handle
if (result != len)
{
LOG_ERROR("J-Link command EMU_CMD_VERSION read failed
(%d)\n", result);
return ERROR_JTAG_DEVICE_ERROR;
}
The crazy thing is that sometimes this works. Often enough to be
usable actually. I added a check to jlink_usb_read and it makes it
fail every time. I attached the patch as I think it is the right
thing to do anyways. If you increase JLINK_IN_BUFFER_SIZE to
something big enough, it will keep it functional.
I don't have any experience with low level jtag interfacing, what is
this code trying to do? Should something other than "J-" be returned
after EMU_CMD_VERSION?
Wish I had more time to debug this tonight, but if I don't get home
for memorial day weekend the GF is not going to be too happy :-)
Dylan
_______________________________________________
Openocd-development mailing list
[email protected]
https://lists.berlios.de/mailman/listinfo/openocd-development
