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

[Detlev Zundel <dzu@denx.de>]

Hi Scott,

> On Wed, 17 Nov 2010 13:42:43 +0100
> Detlev Zundel <dzu@denx.de> wrote:
>
>> > Yes, a simple C tool to take an existing PBL or RCW dump and "espi-ize"
>> > it into a PBL dump would be nice.  The user will still need to acquire
>> > the existing RCW manually.  This only needs to be done once on a board;
>> > it's not part of building a U-Boot image.
>> 
>> @Scott: What is meant by "acquiring the existing RCW"?  Can't we have a
>> tool that is fed with a value for RCW?
>
> I mean that a simple tool could take an existing RCW and modify it for
> espi boot, but it needs to take as input an RCW that is valid for other
> parameters.
>
> The least error prone way to do this, for a user that wants to take a
> board that's already successfully booting from NOR and make it boot
> from eSPI, is to extract the RCW they're already using from the board.

Ok, thanks for the explanation.

> 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.

>> > 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?

Cheers
  Detlev

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