[U-Boot-Users] Ideas on U-Boot configuration with FDT

[Timur Tabi <timur@freescale.com>]

Wolfgang Grandegger wrote:

>      CPU:  MPC5200 v1.0, Core v1.1 at 396 MHz
>            Bus 132 MHz, IPB 66 MHz, PCI 33 MHz
>      FDT:  FDT_ERR_BADMAGIC (or OK, or version number?)
> 
>     At this level also the compatibility of the FDT tree could be checked
>     using fdt_boardcheck().

I think fdt_checkboard() (or boardcheck) should be run from inside the fdt_open_into() 
command.  This takes advantage of the existing mechanism of fdt_open_into() to return an 
error.  It also allows for a device tree to be opened after U-Boot has booted.

> - After relocation, the blob is copied into memory via fdt_open_into()
>    to a defined place and "fdt" is updated accordingly. 

So we'll need to have CFG_FDT_ADDR_FLASH and CFG_FDT_ADDR_RAM.

> Not sure, what
>    location in RAM to use, but it should fit into the existing scheme.
>    Any recommendations?
> 
> - When U-Boot is up, "fdt" points to a valid FDT, e.g. "fdt addr" is not
>    necessary.

I think this feature needs to be optional.  That is, if CFG_FDT_ADDR_xxx are defined, then 
we can enable this feature.  Otherwise, fdt_addr will still be necessary.  Remember, we'll 
still need to support architectures that don't have device trees.

-- 
Timur Tabi
Linux Kernel Developer @ Freescale