* [U-Boot-Users] AT91RM9200 -> UBoot and arm/thumb interworking
@ 2004-07-15 3:30 Erick Castillo
2004-07-15 7:47 ` Wolfgang Denk
0 siblings, 1 reply; 2+ messages in thread
From: Erick Castillo @ 2004-07-15 3:30 UTC (permalink / raw)
To: u-boot
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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* [U-Boot-Users] AT91RM9200 -> UBoot and arm/thumb interworking
2004-07-15 3:30 [U-Boot-Users] AT91RM9200 -> UBoot and arm/thumb interworking Erick Castillo
@ 2004-07-15 7:47 ` Wolfgang Denk
0 siblings, 0 replies; 2+ messages in thread
From: Wolfgang Denk @ 2004-07-15 7:47 UTC (permalink / raw)
To: u-boot
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"?
> 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.
> 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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>
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And please, don't post HTML.
Best regards,
Wolfgang Denk
--
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd@denx.de
I have a very small mind and must live with it. -- Edsger Dijkstra
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