[U-Boot] [PATCH 3/6] SPL: Port SPL framework to powerpc

[Stefan Roese <sr@denx.de>]

On 08/24/2012 09:15 PM, Tom Rini wrote:
>>> I still would like to move to my suggestion to not copy the header and
>>> use the mkimage header values ih_load and ih_ep directly. Right now I
>>> don't see any showstopper for doing it this way. I'll send a patch to
>>> change this shortly (if everything works out).
>>
>> Hmmm. As it seems some SPL loading drivers (block like mmc, streaming
>> like ymodem) are not that easily converted to skipping the header. So
>> I'm not so sure if we should go this way after all...
> 
> Maybe I'm missing something, but maybe we just need to mimic the
> behavior full U-Boot does and if we haven't been loaded where we need to
> execute, shift bits around?

Of course its possible. The main problem is speed here. With the
"problematic" drivers like mmc, you would need to copy the image a 2nd
time, once from MMC to a temp. SDRAM location, and then to its final
(load_addr) destination. With the current approach, the image is only
copied once from MMC to SDRAM. The 2nd copy shouldn't take that long
though. Its SDRAM to SDRAM after all.

I really do like Daniel's approach, with the decompression support:

http://dev.phrozen.org/gitweb/?p=uboot-upstream.git;a=commitdiff;h=39165fa145b2d959f1eaa6faa3ab3053823bb985

We should try to merge this into the current SPL framework. I'll try to
look into this next week.

Thanks,
Stefan