[U-Boot] [PATCH] arm: Tegra2: add support for A9 CPU init

[Tom Warren]

Albert,

On Sun, Mar 13, 2011 at 10:46 AM, Albert ARIBAUD <albert.aribaud at free.fr> wrote:
> Le 16/02/2011 21:26, Tom Warren a écrit :
>>
>> Signed-off-by: Tom Warren<twarren at nvidia.com>
>> ---
>>  arch/arm/cpu/armv7/start.S                 |    6 +
>>  arch/arm/cpu/armv7/tegra2/Makefile         |    2 +-
>
>>  arch/arm/cpu/armv7/tegra2/ap20.c           |  490
>> ++++++++++++++++++++++++++++
>
> This one has an extra empty line at end of file.
>
Thanks - I'll remove it.

>> +void cold_boot(void)
>> +{
>> +       asm volatile(
>> +
>> +       "msr     cpsr_c, #0xd3            \n"
>> +       /*
>> +       * Check current processor: CPU or AVP?
>> +       * If AVP, go to AVP boot code, else continue on.
>> +       */
>> +       "mov     r0, %0                   \n"
>> +       "ldrb    r2, [r0, %1]             \n"
>> +       /* are we the CPU? */
>> +       "cmp     r2, %2                   \n"
>> +       "mov     sp, %3                   \n"
>> +       /* leave in some symbols for release debugging */
>> +       "mov     r3, %6                   \n"
>> +       "str     r3, [sp, #-4]!           \n"
>> +       "str     r3, [sp, #-4]!           \n"
>> +       /*  yep, we are the CPU */
>> +       "bxeq     %4                      \n"
>> +       /* AVP Initialization follows this path */
>> +       "mov     sp, %5                   \n"
>> +       /* leave in some symbols for release debugging */
>> +       "mov     r3, %6                   \n"
>> +       "str     r3, [sp, #-4]!           \n"
>> +       "str     r3, [sp, #-4]!           \n"
>> +
>> +       /* Init and Start CPU */
>> +       "b       startup_cpu              \n"
>> +       :
>> +       : "i"(NV_PA_PG_UP_BASE),
>
> If I'm not mistaken, NV_PA_PG_UP_BASE could be used just as well directly in
> the asm statement instead of via %0 and i(), as anyway the asm will be
> preprocessed and the macro will turn to a number. That would simplify the
> asm instruction as a whole and make the asm statement more understandable
> (also applies to other macros used similarly).
>
Yeah, this code came this way from our bringup group for out in-house
bootloader, and it's always been confusing.
I'll try to simplify it when I incorporate Peter's critiques. Thanks.
> Apart from that, I must admit I don't know the Tegra2/A9 well enough to
> comment further.
>
> amicalement,
> Amicalement,
> --
> Albert.
Thanks for the input,
Tom
>