Raspberry Pi RTEMS applications JTAG debugging and U-boot TFTP image load

[Pavel Pisa]

Hello everybody,

I have decided to prepare debugging environment
during my attempts to test graphic Qiao Yang's
framebuffer support for RPi and I expect that infomation
can be interesting for more developers.

The first, I do not like to copy RTEMS image each time
to SD card for test on real hardware.
So I have setup TFTP server on my computer and use
next uEnv.txt sequence

serverip=192.168.1.10
ipaddr=192.168.1.33
bootargs=place_for_kernel_options
bootcmd=mw.l 0x20200000 0x04a020; mw.l 0x20200008 0x65b6c0; usb start; tftp ${kernel_addr_r} 192.168.1.10:/rpi/rtems/app.img ; bootm 
${kernel_addr_r}

the tftp command can be replaced by dhcp for dynamic network setup.

The first two memory modifications are used to enable
JTAG pins on RPi P1 connector.

The RTEMS executable is conevrted to U-boot image by next commands
sequence

arm-rtems4.11-objcopy -R -S --strip-debug -O binary ticker.exe ticker.bin || exit 1
cat ticker.bin | gzip -9 >ticker.gz
mkimage -A arm -O rtems -T kernel -a 0x00008000 -e 0x00008000 -n "RTEMS" -d ticker.gz ticker.img

The debugger setup is described on our university department group HW notes page

  https://rtime.felk.cvut.cz/hw/index.php/Raspberry_Pi#Raspberry_Pi_JTAG_debugguing

I have used JTAG pod which I know best (i.e. PiKRON JT_USB5/JT_USB6) but
all other FT2232 JTAGs should be usable with similar setup.

Files for DDD and JTAG setup can be found in my RPi utilites repo

  https://github.com/ppisa/rpi-utils/tree/master/jtag-debug

uEnv.txt setup is switched for Linux kernel by default but RTEMS
alternative line can be found there.

To debug system it worth to insert some loop or wait to the system
startup to have time to connect by JTAG to the system and then
allow to continue by forcing jump out of the loop by debugger.

Alternative is to use directly gdb load command from the debugger
session but for some reasons I have for more HW and SW combinations
received that some words has been loaded incorrectly/skipped
if I use load directly from gdb/DDD command line.

I think that it worth to collect/archive the part of RTEMS specific
information even in RTEMS wiki. But there is no RPi page there yet

  https://devel.rtems.org/wiki/TBR/BSP

What should be the name of the page?
Is RaspberryPi good choice to match "raspberrypi" BSP name
in RTEMS.

Best wishes,

            Pavel