[OpenOCD-user] Unable to perform single stepping on Raspberry Pi 2 with FTDI FT2232H

[Bob M <bo...@el...>]

I'm trying to perform single stepping on a Raspberry Pi 2, but it fails 
to single-step - it just runs on without stopping. The problem does not 
occur when I attempt to do exactly the same thing (albeit with different 
OCD config files) with a Raspberry Pi 3 using exactly the same 
kernel7.img, same build of OpenOCD.

   Open On-Chip Debugger
   > halt
   bcm2836.cpu0: MPIDR level2 0, cluster f, core 0, multi core, no SMT
   target halted in ARM state due to debug-request, current mode:
   Hypervisor
   cpsr: 0x000001da pc: 0x00008004
   MMU: disabled, D-Cache: disabled, I-Cache: disabled
   > step
   timeout waiting for target halt

   >

I've created a minimal repository at 
https://github.com/electricworry/openocd-raspberry-pi-2b which - through 
the short Makefile - shows exactly what I'm running and the OpenOCD 
config files I'm using.

For the RPi3, I've taken the existing configs from the project - 
rpi3.cfg, minimodule.cfg (the FT2232H), and bcm2837.cfg. For the RPi2, 
there's no rpi2.cfg in the repo, so I've copied rpi3.cfg and modified it 
to import the bcm2836.cfg file which I think should be the right thing 
to do.

I'm only a beginner user of openocd and JTAG so debugging this 
particular problem is beyond my current knowledge. But if anyone has any 
pointers about how to proceed with investigating the problem I would be 
happy to try, and if it gets resolved I'll submit a patch and config for 
the board.

Alternatively, perhaps someone will tell me that the feature is broken 
on the RPi2 or that there's a simple fix that my scouring of mailing 
lists and forums has not turned up.

Regards,
Bob