u-boot: load a kernel that's in a ubi volume

[anoo]

Hi Joel,

Per our discussion, here are the details of what we’re trying to do 
and the things I’ve tried.

Goal: Have u-boot load a kernel that's in a ubi volume.

1. Added ubi support to uboot by adding the following macros to 
include/configs/ast-g5-ncsi.h temporarily for testing purposes (a new 
config header would probably need to be created for a final 
implementation):

| +#define CONFIG_CMD_UBI
| +#define CONFIG_CMD_UBIFS
| +#define CONFIG_RBTREE
| +#define CONFIG_MTD_DEVICE
| +#define CONFIG_MTD_PARTITIONS
| +#define CONFIG_CMD_MTDPARTS
| +#define CONFIG_LZO

2. Built a romulus image with the above u-boot change plus commit 
https://gerrit.openbmc-project.xyz/#/c/5812/ which is the top-most 
commit for a set of changes to remove the initramfs and create a flash 
image that builds the kernel and rootsfs into ubi volumes.

3. Used the generated obmc-phosphor-image-romulus.ubi.mtd to boot qemu.

4. To be able to use ubi in u-boot, the mtdparts and mtdids variables 
need to be set (reference: 
https://fossies.org/linux/qemu/roms/u-boot/doc/README.ubi).

Here is where I’ve been unable to get u-boot to recognize the existing 
mtd. I’ve tried multiple combinations for mtdids, such as nor0=bmc, 
nor0=<addr>.flash, etc etc. But when running “mtdparts” command from 
u-boot, or a ubi command, always get "Device nor0 not found!”. Ex:

ast# mtdparts
Device nor0 not found!

ast# ubi part kernel0
Device nor0 not found!
Error initializing mtdparts!

I’ve also taken a stab at adding the romulus device tree to u-boot to 
see if that may be the reason, by copying from the kernel and adding to 
u-boot the files arch/arm/dts/aspeed-g5.dtsi, 
aspeed-bmc-opp-flash-layout.dtsi, aspeed-bmc-opp-romulus.dts, and adding 
the dts to the Makefile. Also added a CONFIG_DEFAULT_DEVICE_TREE macro. 
This might not be the correct or complete way to add the device tree to 
the openbmc version of u-boot.


Let me know if you need additional details and thanks in advance for 
your insight.