[U-Boot] RFC unified boot environment

[Tom Rini]

On Tue, Feb 18, 2014 at 10:09:10AM -0600, Dennis Gilmore wrote:

> I'm putting what I have for the documentation so far at the end of this
> email. I think that soc families should have a common settings file,
> each board should have its on file and then we have a common set of
> configurations on how to boot. 

For the next round, please put this into doc/ as part of the first
patch.  Thanks!

[snip]
> fdt_addr_r:
> Mandatory, This is the location where the sysboot/pxeboot with load the dtb to,
> using the fdtdir/devicetreedir or fdt/devicetree options in the pxe/extlinux
> config file. The location can be anywhere in ram it just needs to not overlap
> with anything, allowing 1 megabyte seems to be a safe option.
> 
> ramdisk_addr_r:
> Mandatory, This is the location where the sysboot/pxeboot with load the
> initramfs to, using the initrd option in the pxe/extlinux config file, the
> location of the initramfs does not matter, there needs to be enough room to be
> able to store any image. Making the image the last item stored should allow for
> any initramfs to fit and not overwrite anything else.
> 
> kernel_addr_r:
> Mandatory, 
> 
> pxe_addr_r:
> Mandatory, used by the PXE code to hold the pxelinux config file. The location
> can be anywhere in ram it just needs to not overlap with anything, allowing 1 
> megabyte seems to be a safe option.
> 
> scriptaddr:
> Mandatory, 
> 
> suggested mapping:
> 16M 

We need to talk much more about the suggested mapping as there's a few
hard requirements that must be obeyed.  The device tree _must_ be placed
within kernel accessible low mem and not overwritten by zImage
decompression.  A reference to Documentation/arm/Booting in the kernel
would also be helpful and then summarize saying kernel_addr_r should be
above 32MiB and below 128MiB from the base of system ram.

-- 
Tom
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