[ECOS] Redboot and tumb instructions

kross@elands.co.nz kross@elands.co.nz
Thu Apr 14 06:05:00 GMT 2005

Hi People,

I'm porting redboot to my board (based on ARM AT91FR40162 like EB40A). I have
succeed in installing a feature cut down version onto the board.

The full version gives me:

Error: bad instruction `mrc p15,0,r3,c0,c0,0'

when compiling hal/arm/arch/current/src/arm_stub.c

The section in arm_stub.c at issue is:

// return non-zero for v5 and later
static int
unsigned id;

asm volatile ("mrc p15,0,%0,c0,c0,0\n"
: "=r" (id) : /* no inputs */);

return ((id >> 16) & 0xff) >= 5;

A work-around is to not use ARM thumb interworking. This is ok but are we able to
use thumb (which should result in smaller code) with redboot?


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