[U-Boot,4/8] orion5x: Allow SDRAM initialization to be omitted

For the TS-7800, the FPGA contains a bootloader which handles
the SDRAM initialization and loads a bootloader from RAM. We
should not try to initialize RAM again while running from it.

Signed-off-by: Michael Spang <mspang@csclub.uwaterloo.ca>
---
 arch/arm/cpu/arm926ejs/orion5x/lowlevel_init.S |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

Le 29/01/2011 02:00, Michael Spang a écrit :
> For the TS-7800, the FPGA contains a bootloader which handles
> the SDRAM initialization and loads a bootloader from RAM. We
> should not try to initialize RAM again while running from it.
>
> Signed-off-by: Michael Spang<mspang@csclub.uwaterloo.ca>
> ---
>   arch/arm/cpu/arm926ejs/orion5x/lowlevel_init.S |    4 ++++
>   1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/cpu/arm926ejs/orion5x/lowlevel_init.S b/arch/arm/cpu/arm926ejs/orion5x/lowlevel_init.S
> index 0523bd4..37d7d14 100644
> --- a/arch/arm/cpu/arm926ejs/orion5x/lowlevel_init.S
> +++ b/arch/arm/cpu/arm926ejs/orion5x/lowlevel_init.S
> @@ -86,6 +86,8 @@
>
>   lowlevel_init:
>
> +#ifndef CONFIG_SKIP_SDRAM_INIT
> +
>   	/* Use 'r4 as the base for internal register accesses */
>   	ldr	r4, =ORION5X_REGS_PHY_BASE
>
> @@ -289,5 +291,7 @@ lowlevel_init:
>   	orr	r2, r2, r6
>   	str	r2, [r3, #0x484]
>
> +#endif
> +
>   	/* Return to U-boot via saved link register */
>   	mov	pc, lr

That's basically making lowlevel_init empty, so I would prefer that you 
put #ifdef/#endif around the call to lowlevel_init in start.S and modify 
the orion5x Makefile to include lowlevel_init.S only if 
CONFIG_SKIP_DRAM_INIT is not defined.

(come to think of it, CONFIG_SKIP_LOWLEVEL_INIT is a bit of a misnomer 
since it actually skips not only lowlevelinit but also cpu_init_crit. 
Possibly one could even go as far as renaming CONFIG_SKIP_LOWLEVEL_INIT 
to CONFIG_SKIP_CPU_INIT_CRIT, and then reuse CONFIG_SKIP_LOWLEVEL_INIT 
for lowlevel_init; but that can be a separate patch, with a nifty doc 
update.)

Amicalement,

On Sat, Jan 29, 2011 at 2:36 AM, Albert ARIBAUD <albert.aribaud@free.fr> wrote:
> Le 29/01/2011 02:00, Michael Spang a écrit :
>>
>> For the TS-7800, the FPGA contains a bootloader which handles
>> the SDRAM initialization and loads a bootloader from RAM. We
>> should not try to initialize RAM again while running from it.
>>
>> Signed-off-by: Michael Spang<mspang@csclub.uwaterloo.ca>
>> ---
>>  arch/arm/cpu/arm926ejs/orion5x/lowlevel_init.S |    4 ++++
>>  1 files changed, 4 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/arm/cpu/arm926ejs/orion5x/lowlevel_init.S
>> b/arch/arm/cpu/arm926ejs/orion5x/lowlevel_init.S
>> index 0523bd4..37d7d14 100644
>> --- a/arch/arm/cpu/arm926ejs/orion5x/lowlevel_init.S
>> +++ b/arch/arm/cpu/arm926ejs/orion5x/lowlevel_init.S
>> @@ -86,6 +86,8 @@
>>
>>  lowlevel_init:
>>
>> +#ifndef CONFIG_SKIP_SDRAM_INIT
>> +
>>        /* Use 'r4 as the base for internal register accesses */
>>        ldr     r4, =ORION5X_REGS_PHY_BASE
>>
>> @@ -289,5 +291,7 @@ lowlevel_init:
>>        orr     r2, r2, r6
>>        str     r2, [r3, #0x484]
>>
>> +#endif
>> +
>>        /* Return to U-boot via saved link register */
>>        mov     pc, lr
>
> That's basically making lowlevel_init empty, so I would prefer that you put
> #ifdef/#endif around the call to lowlevel_init in start.S and modify the
> orion5x Makefile to include lowlevel_init.S only if CONFIG_SKIP_DRAM_INIT is
> not defined.
>
> (come to think of it, CONFIG_SKIP_LOWLEVEL_INIT is a bit of a misnomer since
> it actually skips not only lowlevelinit but also cpu_init_crit. Possibly one
> could even go as far as renaming CONFIG_SKIP_LOWLEVEL_INIT to
> CONFIG_SKIP_CPU_INIT_CRIT, and then reuse CONFIG_SKIP_LOWLEVEL_INIT for
> lowlevel_init; but that can be a separate patch, with a nifty doc update.)

I've done the latter change. I thought about moving the call to
lowlevel_init outside of cpu_init_crit, but I doubt it is useful to do
board-specific initialization without also initializing the CPU.

I've also removed the annotation that CONFIG_SKIP_LOWLEVEL_INIT option
is ARM-only, because there is one mips board (vct) that uses this
option.

Michael