[U-Boot] uboot to read kernel and rootfs from a bootfs.

[C Michael Sundius]

we are supporting several platforms and have a well established format and
set of tools for upgrading our images and rolling back to prior images upon
upgrade failure.

that said we'd like to use the same layout for our boot file system and not
mtd partitions for
kernel, rootfs etc.

to boot we read the kernel and a squashfs rootfs and boot them. we'd like
to have u-boot do the same. on intel of course our bootfs is a fat file
system, on our arm platform we have a spi-(nor)-flash
which holds the persistent memory so we'll have to put the boot fs there.
like this:

device nor0 <is25lp512-flash.0>, # parts = 6
 #: name                size            offset          mask_flags
 0: SPL                 0x00020000      0x00000000      0
 1: u-boot              0x00080000      0x00020000      0
 2: fdt                 0x00020000      0x000a0000      0
 3: u-boot-env1         0x00020000      0x000c0000      0
 4: u-boot-env2         0x00020000      0x000e0000      0
 5: bootfs              0x03f00000      0x00100000      0

we were thinking that jffs2 would be best for the bootfs since we gain the
wear leveling. There are really only a few files in the bootfs and not much
r/w activity except on upgrades of images and boot, so I don't think we'll
have a problem mount time or gc,

I looked briefly at ubifs but it seems that uses abotu 10% more space and
we are really looking to be close on space so I am avoiding this.

of course we could stick w/ fat, but of course that does not give us the
wear leveling.

My questions:
1) does u-boot support the use of jffs2 on spi-nor-flash? seems like I get
the error:
get_fl_mem: unknown device type, using raw offset!
when I try to read the fsinfo or fsls. if I just remove that error allowing
get_fl_mem() to return the offset, then I get all 0 and I don't think its
reading the correct data.

should I have CONFIG_CMD_FLASH turned on? was thinking that that was for
"nor" flash that is direct mapped. rather than spi

2) Is jffs2 still supported or should I be using ubi? or maybe just use the
fatfs... if I am largely filling up the flash with my bootfs, then does it
really mater if I'm wear leveling? will I run into fragmentation problems
w/ fat?