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From: Darren Stevens <darren@stevens-zone.net>
To: Michael Ellerman <mpe@ellerman.id.au>
CC: linuxppc-dev@lists.ozlabs.org, Pat Wall <pjwall@mac.com>, rtd@a-eon.com,
 aperez@alexperez.com, Christian Zigotzky <chzigotzky@xenosoft.de>
Date: Mon, 23 Jan 2017 19:15:25 +0000 (GMT)
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Subject: Re: powerpc/pasemi/nemo: Fix low memory values for boot.
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Hello Michael

On 23/01/2017, Michael Ellerman wrote:
>> Clearing the long long at addr 8 has been shown to fix this, so
>> add an initalisation to head_64.S so the system will boot.
>
> I'd really prefer it if someone could tell me why we need to clear it.
> But I assume no one knows?

The problem was found by Christian, and the fix comes courtesy of Olof
Johansson, I've not looked into it before.

> I don't want to pollute this code with NEMO workarounds if we can avoid
> it.

To be honest, so would I.

> You said the hang happens after printing the initial memory map, I'm not
> quite sure where you mean, but it sounds like that will be late enough
> that we can do the clear in pasemi platform code?

During prom_init. Where it says 'Memory layout at Init'

I took a long look today and traced the problem the 'prom_find_boot_cpu' and a
much better patch will follow.

Regards
Darren