dreamplug spi partitions

[Jason Cooper]

On Thu, Aug 09, 2012 at 08:47:57AM +0100, Ian Campbell wrote:
> Hi all,
> 
> I've been using "fw_printenv" and "fw_setenv" from the u-boot-tools
> package on my DreamPlug which work fine with this /etc/fw_env.config:
>         # Configuration file for fw_(printenv/saveenv) utility.
>         # Up to two entries are valid, in this case the redundant
>         # environment sector is assumed present.
>         # MTD device name       Device offset   Env. size       Flash sector size
>         /dev/mtd1               0x00000000      0x00001000      0x00001000
>         
> This corresponds roughly, but not exactly, with:
>         # cat /proc/mtd 
>         dev:    size   erasesize  name
>         mtd0: 00080000 00001000 "u-boot"
>         mtd1: 00010000 00001000 "u-boot env"
>         mtd2: 00010000 00001000 "dtb"
> 
> But notice how "Env. size" and mtd1's size don't match -- if I use
> 0x10000 in fw_env.cfg then the tools don't work (checksums don't match).

I've always seen the u-boot environment set to 4k.  The kernel
partitions came out of my head.  When I added support for the dreamplug
to u-boot, I found out there was a bug in the factory supplied u-boot
which only allowed it to see the first 1MB of the 2MB flash.  Also, the
factory supplied kernel didn't even have support for the flash.

So, I fixed u-boot, and figured the extra 1MB was too small for a
kernel, wasn't used by anybody else, and imho, the factory location of
the environment didn't leave much room for new u-boots.

I decided to move the environment and make a place for the dtb.  As I
didn't want to constrain either one, I split the extra space between the
two.

Was that the best decision?  Well, no one yelled at me and I was new to
the whole process, so that's how it went down.

As it is right now, if you configure your own u-boot to have, say
0x10000 bytes for the environment, you don't need to change your kernel
to support it.  Just set the size and write it.

I'm open to suggestions and patches...

hth,

Jason.