[U-Boot] [PATCH 2/2][v2] Add readme of how to boot from espi flash for p4080ds.

[Kumar Gala]

>> Creating an RCW from scratch is more complicated, which is why we
>> have that javascript tool -- though we could provide some example RCWs
>> for common configs.
> 
> Just for my information - it sounds like the RCW is really complex.  If
> RCW still expands to "reset control word", I would expect it to be 32
> bits though.  It is rather common for U-Boot porters to determine 32-bit
> values for specific registers without using a javascript tool, so maybe
> I'm wrong here.

On P4080 (and future devices) it is 512 bits of data so not as trivial as our older parts that used a simple 32-bit RCW.

>>>> This README describes how to build an Image can be used by PBL (pre-boot
>>>> loader), building u-boot image is the first step, then RCW, PBI
>>>> commands, XXD dump of u-boot.bin, the tool will combine the RCW and PBI
>>>> and XXD dump together to produce the PBL XXD file, suppose the PBL XXD
>>>> file is saved as x.xxd, we need to run "xxd -r x.xxd > pbl_image.bin" to
>>>> produce the final PBL Image. Take a look at the whole process, I see no
>>>> way it can be scripted / automatized.
>>> 
>>> I said it once before, look at how kwbimage wraps up u-boot.bin into
>>> such an "augmented" image.  If the Marvell guys can do this for their
>>> platform, I see no reason why this cannot be done for your platform.
>> 
>> Sure, once you have a valid input RCW it should be possible to automate
>> the rest.
> 
> For the supported configurations the RCW should be provided of course,
> so I do not see a big problem here?

Agreed, we should be provide a default RCW for the boards as part of u-boot.

- k