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Redboot and tumb instructions
- From: "kross at elands dot co dot nz" <kross at elands dot co dot nz>
- To: ecos-discuss at sources dot redhat dot com
- Date: Thu, 14 Apr 2005 18:04:47 +1200
- Subject: [ECOS] Redboot and tumb instructions
- Reply-to: kross at elands dot co dot nz
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
v5T_semantics(void)
{
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?
Regards,
Keith
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