pi@raspberrypi:~/tomu-bootloader/openocd $ sudo openocd -f tomu-flash.conf
Open On-Chip Debugger 0.10.0+dev-00001-g0ecee83 (2017-01-23-19:52)
Licensed under GNU GPL v2
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
BCM2835 GPIO nums: swclk = 25, swdio = 24
adapter speed: 1000 kHz
cortex_m reset_config sysresetreq
Info : BCM2835 GPIO JTAG/SWD bitbang driver
Info : SWD only mode enabled (specify tck, tms, tdi and tdo gpios to add JTAG mode)
Info : clock speed 1006 kHz
Info : SWD DPIDR 0x0bc11477
Info : efm32hg309.cpu: hardware has 0 breakpoints, 0 watchpoints
Error: Failed to enable the FPB
Polling target efm32hg309.cpu failed, trying to reexamine
Info : efm32hg309.cpu: hardware has 0 breakpoints, 0 watchpoints
Error: Failed to enable the FPB
Polling target efm32hg309.cpu failed, trying to reexamine
Info : efm32hg309.cpu: hardware has 0 breakpoints, 0 watchpoints
    TargetName         Type       Endian TapName            State
--  ------------------ ---------- ------ ------------------ ------------
 0* efm32hg309.cpu     cortex_m   little efm32hg309.cpu     unknown
target halted due to debug-request, current mode: Thread
xPSR: 0x61000000 pc: 0x00002dec msp: 0x20000938
target halted due to debug-request, current mode: Thread
xPSR: 0x61000000 pc: 0x00002dec msp: 0x20000938
** Programming Started **
auto erase enabled
Info : detected part: EFM32 Happy Gecko - Rev: 135
Info : flash size = 64kbytes
Info : flash page size = 1024bytes
Info : SWD DPIDR 0x0bc11477
Error: Failed to read memory at 0x400c000c
Error: Failed to erase page 29
Info : SWD DPIDR 0x0bc11477
Error: Failed to write memory at 0x100003e8
Error: error writing to flash at address 0x00000000 at offset 0x00000000
auto erase enabled
detected part: EFM32 Happy Gecko - Rev: 135
flash size = 64kbytes
flash page size = 1024bytes
SWD DPIDR 0x0bc11477
Failed to read memory at 0x400c000c
Failed to erase page 29
SWD DPIDR 0x0bc11477
Failed to write memory at 0x100003e8
error writing to flash at address 0x00000000 at offset 0x00000000