On 09/28/2011 03:08 AM, Karl Kurbjun wrote:
Hi all,
I have an A9 target where the memory map visible over the AHB versus
what is visible to the processor is slightly different.
On this target the lower 512 kByte block of DDR is not accessible from
the AHB, but the processor is able to see it through the L2
controller. In order to access this memory I can tell OpenOCD to use
the APB DAP port ("dap apsel 1") thanks to Luca's work. With that I
am able to read and write to the memory without trouble within OpenOCD.
While it works within OpenOCD, I run into problems when I try to
connect and start debugging with GDB. I cannot load the application
through GDB without getting messages like the following:
"Ignoring packet error, continuing..."
after loading if I try to set a breakpoint ("b main") I get the
following message:
"Reply contains invalid hex digit 79"
To make sure that this was not a target specific issue I also verified
that this fails on the Pandaboard as well. I attached a -d3 log from
openocd when trying this out on the Pandaboard.
If I do not modify the AP used by the DAP (leave it to use the AHB)
prior to trying to load the application in GDB on the Pandaboard
everything works fine.
Does anyone have any suggestions on what might be causing this failure
while using the APB interface?
Thanks,
Karl
Sorry for the second email right in a row, but I forgot to include an
important piece which may point to the root cause. In order to
reproduce this failure I set the JTAG adapter speed down to 10 kHz on
the Pandaboard. If I set the adapter speed to 1MHz I do not see the
problem.
Looking at the logs it appears that this may be caused by gdb not seeing
a keep_alive packet, but I am not sure where a keep_alive is missing
from the code. It appears that OpenOCD is sending the packets often
enough when the speed is high enough and the DAP AP is the AHB, but the
combination of the slow cable speed and using the APB appears to cause a
timeout.
-Karl
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