[U-Boot] Standalone API examples on the P4080DS

[U-Boot] Standalone API examples on the P4080DS

[David George]

Hi all,

I have compiled the hello_world standalone API example documented at 
http://www.denx.de/wiki/view/DULG/UBootStandalone for the Freescale 
P4080DS development board.

For the standalone api example hello_world, the tutorial (linked above) 
states that the entry point of the application *is offset 4 bytes from 
the start of the file* (I.E. address 0x40004).

With all build settings at default, my standalone base address is 
0x40000 (defined in arch/powerpc/config.mk). This produces the following 
object code:

00040000 <hello_world>:
    40000:	94 21 ff e0 	stwu    r1,-32(r1)
    40004:	7c 08 02 a6 	mflr    r0
    40008:	bf 61 00 0c 	stmw    r27,12(r1)
    4000c:	7c 7e 1b 78 	mr      r30,r3
    40010:	7c 83 23 78 	mr      r3,r4
    40014:	90 01 00 24 	stw     r0,36(r1)

It looks like the entry point is 0x40000. Why does the tutorial state 
that the example needs to be run from a 4 byte offset? In this case this 
will result in a failure to create a stack frame for hello_world.

Thanks!

Dave George

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[U-Boot] Standalone API examples on the P4080DS

[Peter Tyser]

Hi David,


> It looks like the entry point is 0x40000. Why does the tutorial state
> that the example needs to be run from a 4 byte offset? In this case 
> this
> will result in a failure to create a stack frame for hello_world.

For PowerPC the entry point used to be non-deterministic, but was 
generally 0x40004 which is where the wiki value came from.  The 
following 2 patches made the entry point consistently 0x40000:

http://git.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=commit;h=620bbba524fbaa26971a5004793010b169824f1b

http://git.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=commit;h=c91d456c055237bdadb99a80e198748b8cf32595

I updated the wiki to match the newer 0x40000 address, which is valid 
for PowerPC boards with a comment to check out 
CONFIG_STANDALONE_LOAD_ADDR for other architectures.

Peter

[U-Boot] Standalone API examples on the P4080DS

[David George]

Thank you very much for this Peter, it's much appreciated, and should 
hopefully stop anyone else falling into the same trap!

Thanks!

Dave George

On 16/01/2015 17:08, Peter Tyser wrote:
> Hi David,
>
>
>> It looks like the entry point is 0x40000. Why does the tutorial state
>> that the example needs to be run from a 4 byte offset? In this case
>> this
>> will result in a failure to create a stack frame for hello_world.
>
> For PowerPC the entry point used to be non-deterministic, but was
> generally 0x40004 which is where the wiki value came from.  The
> following 2 patches made the entry point consistently 0x40000:
>
> http://git.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=commit;h=620bbba524fbaa26971a5004793010b169824f1b
>
> http://git.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=commit;h=c91d456c055237bdadb99a80e198748b8cf32595
>
> I updated the wiki to match the newer 0x40000 address, which is valid
> for PowerPC boards with a comment to check out
> CONFIG_STANDALONE_LOAD_ADDR for other architectures.
>
> Peter
>

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