AT91RM9200 -> UBoot and arm/thumb interworking
Hello,
I'm getting started with an AT91RM9200 development kit from atmel and am having trouble starting a simple application with UBoot. If I compile my application into 32bit arm code only, I can successfully load and run some simple startup code through the 'loadb' and 'go' commands that UBoot offers.
I have two files: startup.s and main.c. "startup.s" does nothing more than set up some vector branches, initializes a stack, and jumps to main. All main does is drive a user led on the development board. As I said, compiling this in 32 bit arm seems to work fine when I load to 0x2000 0000. If I try to compile the main.c source code in thumb mode, then the 'bx' branch to main fails and the code does not run. The code preceding the branch is:
.
ldr r0, =main
mov r13, pc
bx r0
I was wondering if there was some initializations made by UBoot that would prevent it from loading thumb code. Any help/ideas would be especially useful. Thanks.
--Erick
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Quoted 5 lines · In message <200407142030211.SM00572@ENG2> you wrote:
I'm getting started with an AT91RM9200 development kit from atmel and am having trouble starting a simple application with UBoot. If I compile my application into 32bit arm code only, I can successfully load and run some simple startup code through the 'loadb' and 'go' commands that UBoot offers.
What do you mean with "startup code"?
Quoted 2 lines
I have two files: startup.s and
main.c. "startup.s" does nothing more than set up some vector branches, initializes a stack, and jumps to main. All
Ummm... Whay are you doing this? U-Boot provides a standard C environment to you, no special startup code is needed. Did you find the code in the examples/ directory? This shows what you need to get a standalone application running under U-Boot.
Quoted 3 lines
I was wondering if there was some initializations made by UBoot that would prevent it from loading thumb code. Any help/ideas would be especially useful. Thanks.
Well, if you mess with the environment like stack and exception vectors etc. you should not be surprised when U-Boot is crashing on you.
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And please, don't post HTML.
Best regards,
Wolfgang Denk
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