Re: [Celinux-dev] CELF Project Proposal- Refactoring Qi, lightweight bootloader

[Andy Green <andy@warmcat.com>]

On 12/21/09 19:30, Somebody in the thread at some point said:

Hi -

Let me add back the context for this quote:

''While working at Openmoko maintaining their kernel, it became obvious 
that U-Boot was turning into a mini-me for Linux.  Many cut-down Linux 
drivers were appearing there, there was a shell with an environment 
holding private states ...''

>> Another big problem with U-Boot was the inability to update the
>> bootloader from the Linux world.  Instead the bootloader was treated
>> special and had to be updated over USB with DFU (the exclusivity of it
>> enforced by an ECC policy disconnected from Linux, meaning U-Boot had to
>> write it in there).  In Qi, the bootloader can be updated by a packaged
>> update like anything else in the rootfs.
>
> Can you explain to me why it was not possible to update U-Boot from
> Linux? I cannot imagine a reason for such a restriction.

I was talking about GTA02 specifically here, it was (and still is AFAIK) 
only updateable by DFU for the bootloader.  We had kernels with soft ECC 
that differed from the ECC / bad block marking generated and used by the 
s3c2442 NAND hardware unit.  If U-Boot wrote it, it could at least read 
it again.  So DFU was / is the only official way to update GTA02 bootloader.

As you say nothing generally stops update of U-Boot from Linux same as 
anything else can be updated from there, if Linux can write those NAND 
sectors with ECC / BBT that the bootloader can understand or ignore, and 
Linux can understand and comply with / update the BBT scheme of U-Boot.

Another benefit of SD Card boot is that it regularizes the bootloader 
physical storage, so these issues don't exist and it can always be 
updated from Linux.

-Andy