[U-Boot] [RFC PATCH 6/8] omap3_beagle: add nand_spl support

[Aneesh V <aneesh@ti.com>]

John,
On Saturday 08 January 2011 12:16 PM, John Rigby wrote:
> On Fri, Jan 7, 2011 at 11:33 PM, Aneesh V<aneesh@ti.com>  wrote:
>> Hi John,
>>
>> On Tuesday 28 December 2010 06:17 AM, John Rigby wrote:
>>>
>>> Signed-off-by: John Rigby<john.rigby@linaro.org>
>>> +
>>> +void board_init_f(unsigned long bootflag)
>>> +{
>>> +       nand_boot();
>>> +}
>>> +
>>
>> I see that you have added a call to nand_boot() in start.S too.
>> Which is the intended one?
>> If we jump to nand_boot() here bss will not be cleared, right?
>>
>> Also, I see potential issues in start.S that will prevent bss setup for
>> PRELOADERs. I will correct these in my patch.
>>
>> Best regards,
>> Aneesh
>>
>
> The call to nand_boot in board_init_f makes sense for platforms where
> the spl code does not need to be relocated because it has been loaded
> into SRAM by a mask boot rom.  The later nand_boot called from start.S
> is for the traditional nand_spl case where you are typically running
> in a 4K nand controller buffer so the code needs to be relocated to
> dram after dram init.
>
> Of course my only testing has been on OMAP3 which fits the first case.
>   I'm not sure if the second case even matters.  The arm7 platforms I
> know about all have rom boot loaders and large enough SRAM to run the
> spl u-boot in (OMAP[34]) or have boot headers that can be used to init
> dram before loading a full u-boot into dram (i.mx5[13]).
>
> Also, I was thinking that BSS would not be used in PRELOADERs but of
> the large SRAM case it certainly would be useful to have BSS.
>

Agree. So, how about this?
1. Call relocate_code() in board_init_f() with destination address same
as TEXT_BASE
2. start.S skips the relocation, clears the bss(this needs to be fixed)
and calls board_init_r
3. Call nand_boot() in board_init_r

This is what I am planning to do for OMAP4 preloader.

> This is all new territory since previously all platforms using
> nand_spl were of the small sram variety.
>
> John

Thanks,
Aneesh