I'm wondering the same thing..

More generally when to JTAG vs. utilizing all of the other tools out there 
for debugging Linux (e.g. GDB server).  

We recently tried to bring up a custom board with the am5718.  We were 
focused on booting the board in stages (e.g. first try to get the SPL to 
boot, then SPL to load u-boot, etc, etc).  Since we were trying to tailor 
(and will still be engaged in this) Linux to work with our hardware, we 
realized that JTAG debugging would probably be useful to figure out what 
the processor is doing and how far the SPL gets.  Then later on, once we 
get u-boot running and the kernel booting, we can switch over to other 
debug tools.. JTAG may also be useful for debugging some of the other 
processors on the Sitara chip which don't run Linux such as the PRU, C66 
DSPs and IPU's... but don't yet have any experience with that..

Our initial board design (now being re-spun) with the 5718 only provided a 
UART for console on UART 10 (with the allowed IO sets/ pad configuration), 
thus we attempted to switch from UART 3 to 10, but could get nothing to 
come out on the console.  We hooked up the blackhawk JTAG connector to the 
custom board (which populates JTAG), to attempt to look for "signs of life" 
on the processor and on the board.  We were able to see that the processor 
wasn't correctly responding to the JTAG tests initiated by CCS.  We then 
connected JTAG to the BeagleBoard-X15's JTAG and were able to run through 
the JTAG test procedure and view the 5728's internal registers.  We haven't 
yet gotten around to loading the SPL with symbol information via CCS to the 
JTAG, but this might be something we try to do once the next revision of 
our board comes in..

Hopefully this is helpful...



On Tuesday, June 13, 2017 at 12:47:14 PM UTC-5, [email protected] wrote:
>
>
> BBB: Do I gain anything by adding the JTAG header and using a JTAG debug 
> pod?
>

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