[U-Boot] Got u-boot-2012.10 running on at91sam9200 - but why does it work?

[U-Boot] Got u-boot-2012.10 running on at91sam9200 - but why does it work?

[Arvid Brodin]

Hi,

I managed to get u-boot-2012.10 to boot from NOR flash on a custom 
at91rm9200 board by doing this:


Signed-off-by: Arvid Brodin <arvid.brodin@xdin.com>
---
 arch/arm/cpu/arm920t/start.S   | 8 +++-----
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/arm/cpu/arm920t/start.S b/arch/arm/cpu/arm920t/start.S
index 14c9156..efc4ea3 100644
--- a/arch/arm/cpu/arm920t/start.S
+++ b/arch/arm/cpu/arm920t/start.S
@@ -294,9 +294,7 @@ clbss_e:
 _nand_boot_ofs:
 	.word nand_boot
 #else
-	ldr	r0, _board_init_r_ofs
-	adr	r1, _start
-	add	lr, r0, r1
+	ldr	lr, _board_init_r
 	add	lr, lr, r9
 	/* setup parameters for board_init_r */
 	mov	r0, r5		/* gd_t */
@@ -304,8 +302,8 @@ _nand_boot_ofs:
 	/* jump to it ... */
 	mov	pc, lr
 
-_board_init_r_ofs:
-	.word board_init_r - _start
+_board_init_r:
+	.word board_init_r
 #endif
 
 _rel_dyn_start_ofs:
-- 
1.8.1.5

(I also had to comment out the CONFIG_AT91RM9200EK define in my custom board
config file.)

Any idea why this is needed? I simply used a LED to see where the un-touched 
code failed, and noticed it reached the board_init_r call but never entered the
function. I thought it a bit strange to first subtract _start in the variable
definition and the add it again in the code, so I tried without it, and -- lo
and behold! -- it worked.



-- 
Arvid Brodin | Consultant (Linux)
XDIN AB | Knarrarn?sgatan 7 | SE-164 40 Kista | Sweden | xdin.com

[U-Boot] Got u-boot-2012.10 running on at91sam9200 - but why does it work?

[Jens Scharsig]

Hello Arvid,
Am 2013-10-09 21:23, schrieb Arvid Brodin:
> Hi,
> 
> I managed to get u-boot-2012.10 to boot from NOR flash on a custom 
> at91rm9200 board by doing this:
> 
> 
> Signed-off-by: Arvid Brodin <arvid.brodin@xdin.com>
> ---
>  arch/arm/cpu/arm920t/start.S   | 8 +++-----
>  2 files changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/cpu/arm920t/start.S b/arch/arm/cpu/arm920t/start.S
> index 14c9156..efc4ea3 100644
> --- a/arch/arm/cpu/arm920t/start.S
> +++ b/arch/arm/cpu/arm920t/start.S
> @@ -294,9 +294,7 @@ clbss_e:
>  _nand_boot_ofs:
>  	.word nand_boot
>  #else
> -	ldr	r0, _board_init_r_ofs
> -	adr	r1, _start
> -	add	lr, r0, r1
> +	ldr	lr, _board_init_r
>  	add	lr, lr, r9
>  	/* setup parameters for board_init_r */
>  	mov	r0, r5		/* gd_t */
> @@ -304,8 +302,8 @@ _nand_boot_ofs:
>  	/* jump to it ... */
>  	mov	pc, lr
>  
> -_board_init_r_ofs:
> -	.word board_init_r - _start
> +_board_init_r:
> +	.word board_init_r
>  #endif
>  
>  _rel_dyn_start_ofs:
> 

you don't need change start.s to boot from NOR.
If shold set the  #define CONFIG_SYS_TEXT_BASE  0x00000000

Please see the configuration for eb_cpux9k2 board. This board does boot
from NOR with u-boot 2012.10.

BTW
The release 2012.10 is out of date. You should upadte to the current one (2013.10-rc4)

Best regards

Jens

[U-Boot] Got u-boot-2012.10 running on at91rm9200 - but why does it work?

[Arvid Brodin]

On 2013-10-10 10:25, Jens Scharsig wrote:
> Hello Arvid,
> Am 2013-10-09 21:23, schrieb Arvid Brodin:
>> Hi,
>>
>> I managed to get u-boot-2012.10 to boot from NOR flash on a custom 
>> at91rm9200 board by doing this:
>>
>>
>> Signed-off-by: Arvid Brodin <arvid.brodin@xdin.com>
>> ---
>>  arch/arm/cpu/arm920t/start.S   | 8 +++-----
>>  2 files changed, 4 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm/cpu/arm920t/start.S b/arch/arm/cpu/arm920t/start.S
>> index 14c9156..efc4ea3 100644
>> --- a/arch/arm/cpu/arm920t/start.S
>> +++ b/arch/arm/cpu/arm920t/start.S
>> @@ -294,9 +294,7 @@ clbss_e:
>>  _nand_boot_ofs:
>>  	.word nand_boot
>>  #else
>> -	ldr	r0, _board_init_r_ofs
>> -	adr	r1, _start
>> -	add	lr, r0, r1
>> +	ldr	lr, _board_init_r
>>  	add	lr, lr, r9
>>  	/* setup parameters for board_init_r */
>>  	mov	r0, r5		/* gd_t */
>> @@ -304,8 +302,8 @@ _nand_boot_ofs:
>>  	/* jump to it ... */
>>  	mov	pc, lr
>>  
>> -_board_init_r_ofs:
>> -	.word board_init_r - _start
>> +_board_init_r:
>> +	.word board_init_r
>>  #endif
>>  
>>  _rel_dyn_start_ofs:
>>
> 
> you don't need change start.s to boot from NOR.
> If shold set the  #define CONFIG_SYS_TEXT_BASE  0x00000000

But that's just the thing, I *do* need this change for the board to boot. 
CONFIG_SYS_TEXT_BASE is 0x10000000 (this is the base address for the flash 
memory).

Without my patch above, I only get this:

----------
U-Boot 2012.10 (Oct 09 2013 - 02:28:44)

DRAM:  64 MiB
----------

I thought this was a known problem with at91rm9200 booting from NOR flash?
There's at least one other board that I know of with the same problem (the 
Artila Matrix-500).


> Please see the configuration for eb_cpux9k2 board. This board does boot
> from NOR with u-boot 2012.10.

Hmm, you are right. This config does boot my card (after I modify it to suit,
of course). Besides the different CONFIG_SYS_TEXT_BASE, I think the main 
differences to the at91rm9200ek config that I based my earlier config on are 
these things:

#define CONFIG_SYS_BOOT_SIZE		0x00 /* 0 KBytes */
#define CONFIG_SYS_U_BOOT_BASE		PHYS_FLASH_1
#define CONFIG_SYS_U_BOOT_SIZE		0x60000 /* 384 KBytes */

None of these are declared in the at91rm9200ek config.

Unfortunately, I don't have an AT91RM9200EK card, so I can't test if the 
problem I ran in to exists for that card as well using the at91rm9200ek
config.


-- 
Arvid Brodin | Consultant (Linux)
XDIN AB | Knarrarn?sgatan 7 | SE-164 40 Kista | Sweden | xdin.com

[U-Boot] Got u-boot-2012.10 running on at91rm9200 - but why does it work?

[Jens Scharsig]

Hello Arvid,
>>>
>>
>> you don't need change start.s to boot from NOR.
>> If shold set the  #define CONFIG_SYS_TEXT_BASE  0x00000000
> 
> But that's just the thing, I *do* need this change for the board to boot. 
> CONFIG_SYS_TEXT_BASE is 0x10000000 (this is the base address for the flash 
> memory).

YES and NO:
The nor is physical mapped to 0x1000000 that's right.
But during boot from nor the Memory is also mapped to address 0x0.
U-Boot is relocate to ram after ram init. The calculations of the reclocation
process are based on "delta between PC and CONFIG_SYS_TEXT_BASE".

> 
> Without my patch above, I only get this:
> 
> ----------
> U-Boot 2012.10 (Oct 09 2013 - 02:28:44)
> 
> DRAM:  64 MiB
> ----------
> 

So at this position u-boot try to jump to a wrong address or code in ram.

> I thought this was a known problem with at91rm9200 booting from NOR flash?
> There's at least one other board that I know of with the same problem (the 
> Artila Matrix-500).
> 
> 
>> Please see the configuration for eb_cpux9k2 board. This board does boot
>> from NOR with u-boot 2012.10.
> 
> Hmm, you are right. This config does boot my card (after I modify it to suit,
> of course). Besides the different CONFIG_SYS_TEXT_BASE, I think the main 
> differences to the at91rm9200ek config that I based my earlier config on are 
> these things:
> 
> #define CONFIG_SYS_BOOT_SIZE		0x00 /* 0 KBytes */
> #define CONFIG_SYS_U_BOOT_BASE		PHYS_FLASH_1
> #define CONFIG_SYS_U_BOOT_SIZE		0x60000 /* 384 KBytes */
> 
> None of these are declared in the at91rm9200ek config.

This are old items, which needs a clean up.
> 
Regards Jens