[U-Boot-Users] U-Boot-NG ?

[Stefan Roese <sr@denx.de>]

Hi Robert,

On Wednesday 04 July 2007, Robert Schwebel wrote:
> > I'm still a little undecided, if a "simple" output mechanism is
> > enough. Of course you can life with a hardwired baudrate on most
> > systems, so that you don't have to read the environment. But there
> > will be some systems where the user configured a different baudrate
> > and the outputs from the DDR2 init routine will not be readable.
>
> Let's look at the PC architecture, which is really supposed to be
> customized by dummy users. It just makes BEEEP if the memory init goes
> wrong. People designed it this way on purpose. I know that there are
> brain damaged hardware designs in the industry, but please don't let us
> make strategic design decisions based on crappy hardware instead of the
> 95% case. I recognize that it is a good feature for these cases, but
> it's not a good excuse for transferring a straight forward, simple and
> maintainable design into a can of worms.

AFAIK the PC at least supports some kind of beep morse code to differentiate 
between different error sources.

> > If no output on the serial console always means: "problem with
> > memory", than this would be an easy indication for SDRAM problems. But
> > I have seen lots of other errors, that lead to a hangup in the very
> > early boot stage. Most of the time *before* SDRAM is initialized.
>
> Because lots of things are done before the SDRAM is initialized. All
> these would be done later in our design and thus would have access to
> the console.

You're only partly right here. On some platforms there has to happen quite a 
lot before you can begin with the SDRAM setup. Something like TLB setup, 
GPIO-setup, I2C setup comes to my mind right now.

> > Don't get me wrong. I generally like this 2 stage approach. For
> > example it fits the NAND booting support (see nand_spl/*) where a
> > small (4k on 4xx) first stage loader is needed. I'm just a little
> > hesitant about dropping the full featured printf in early boot stages.
>
> I assume the way we do the discussion now is really right - we throw in
> "it can be soooooo easy" ideas, you tell us the corner cases and then we
> iterate until everybody is happy :-)

Yes. Let's continue this way... :-)

Best regards,
Stefan

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