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

[Scott Wood]

On Tue, 16 Nov 2010 23:02:48 +0100
Wolfgang Denk <wd at denx.de> wrote:

> Dear Scott Wood,
> 
> In message <20101116155432.585fa514 at udp111988uds.am.freescale.net> you wrote:
> >
> > > Can you not provide a plain and simple AUTOMATIC way to get this
> > > result? some plain stupid command line tool? Something that works as
> > > a simple "make XXX" ?  So it can be scripted / automatized / used?
> > 
> > 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.
> 
> If this only needs to be done once on a board, then why cannot it be
> included in U-Boot with the configuration for this specific board?

We probably should provide some RCWs as a starting point (we do in the
BSP, outside of the U-Boot component) -- but there are more valid RCWs
than there are U-Bboot configurations.

Besides details about how the board is wired up and where you're
booting from, it depends on what sort of riser cards you have in which
slots, what speed your chip is rated for, etc.

The usual case for NOR flash is a user building U-Boot and flashing
it, while leaving the existing RCW in place -- the RCW is not embedded
in the U-Boot image like it is on 83xx.  This is a fortunate accident
of where the reset vector is located, though.  Other boot sources such
as espi are probably not as lucky.  But even then, you should only need
to create a PBL/RCW once, to be included in all subsequent U-Boot
builds.

-Scott