[U-Boot] [PATCH] 8xx: prevent a machine check in scc_init().

[Wolfgang Denk]

Dear Gary Jennejohn,

In message <20080915105924.3249d5db at peedub.jennejohn.org> you wrote:
>
> The first call to scc_init() executes all the code.  Only subsequent
> calls are short-circuited.

I am aware of that. But after the first call, eth_halt()  might  have
been  run,  deactivating  the  interface; then for example interfaces
might have been switched to another port, and finally  switched  back
to the old port. In this case, a full initialization sequence will be
necessary.

> OK, just think about it a little.

Indeed, please do.

> When nc is active as a console it is often invoked for every byte.

Ah! That's the origin of your concern. But I think you're  trying  to
attack  it  at  the wrong place. Your modification will most probably
break some (or many) boards.

> The network stack code calls eth_init() prior to sending the byte
> and eth_halt() after sending the byte.
> 
> scc_init() happily tries to reallocate dpram at every call when
> CFG_ALLOC_DPRAM is defined, as it was in my case.  Eventually dpram
> is exhausted which evidently results in a machine check.

-> grep -l CONFIG_NETCONSOLE include/configs/* | xargs egrep CFG_ALLOC_DPRAM | wc -l
0
->

You are right. None of the boards that use  netconsole  so  far  (and
that  have  been  tested  with  that  feature,  obviously)  is  using
CFG_ALLOC_DPRAM. So a fix is necessary not to re-allocate DPRAM here.

It would be great if you could submit a patch that fixes this problem.

> I doubt that nc is used very often, otherwise this problem would
> have reared its ugly head a lot sooner.  The general use case is
> also to merely invoke tftp to load the kernel and maybe fdt.
> This succeeds because it takes numerous (in this case about 14)
> calls to the init routine before the machine check happens.

In fact I think the problem never showed before because nodody used
CFG_ALLOC_DPRAM with netconsole. I agree that this should be fixed.

Best regards,

Wolfgang Denk

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