In my bare metal OS running in AArch32 on a Raspberry Pi 3B, I have debug module that responds to exceptions including the breakpoint instruction. I am trying to use the debug capabilities of the processor as described in the Arm8 manual and the Cortex A53 manual.
The processor is running in system mode (0x1F). Only one core is running. I have not turned on security mode.
First I enable breakpoints in the DBGDSCRext register:
mrc p14, 0, r0,c0,c2,2
orr r0,#0x8000 @DBGDSCRext.MDBGen
mcr p14, 0, r0,c0,c2,2
Then set the breakpoint value
mov r0,0x8200 @address of code I want to break on
mcr p14,0,r0,c0,4 @DBGBVR0
Then enable it
mov r0,#1 @enable flag on a address match type
mcr p14,0,r0,c0,5 @DBGBCR0
I'm expecting this to cause an exception just like the breakpoint instruction does (bkpt), but nothing happens when I cause the target code to execute. Can someone see what I am missing?
For what it's worth, today I managed to get this to work on my old Raspberry Pi, the 1B. But I still have no luck with the 3B.
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