[U-Boot-Users] AT91RM9200 boot.bin interaction with u-boot and SDRAM

[Ulf Samuelsson]

>>> Also, is it broadly correct to say that boot.bin does the following:
>>
>> 1. low level init
>> 2. uncompress a gzipped file from SRC in parallel flash and put it in
> SDRAM
>> at DST
>> 3. jump to unzipped file at DST.
>>
>>> If this is the case, then do we need to also ensure that
>>> CONFIG_SKIP_RELOCATE_UBOOT is defined? Is there a point to this aside
> from
>>> saving space in flash?
>
>>I think You need to relocate to SDRAM,
>>if you have linked the U-boot as you mention above.
>
> I agree. However, what I meant was that if boot.bin is already copying the
> unzipped u-boot code to the correct place in SRAM, is there a need for
> u-boot to do the same? Is this in fact what boot.bin does? Have I totally
> missed the point here?
>
> Is boot.bin something that Atmel provided to support a number of potential
> applications like u-boot and can, therefore, be used as a convenience with
> u-boot rather than as a necessity? Suppose I'm just curious really since 
> it
> works in the EK and I'm keen to follow that approach on our board since I
> know it to be good.
>

I think the U-Boot: boot.bin was added after Atmel created the separate 
boot.bin.

Since the AT91 boots from a various of sources, keeping a separate
boot.bin allows you to boot the same U-Boot from any flash memory.
You can store the u-boot in parallel flash, dataflash, NAND flash or 
whatever.

If you use the internal boot.bin, it will only work when programmed into a 
parallel flash.

Note that the environment storage will make this a little fuzzy.
The U-Boot is compiled to store the environment
in a certain type of memory.
If you put it in serial EEPROM (not recommended due to speed)
then you can have a single image which can be booted
from any type of flash, but if you compile for a dataflash environment
storage, you have to have a dataflash there...


Best Regards
Ulf Samuelsson                ulf at atmel.com
Atmel Nordic AB
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