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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Mathieu Malaterre <malat@debian.org>,
        Christophe LEROY <christophe.leroy@c-s.fr>
Cc:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] powerpc: Allow selection of CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
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References: <20180417104909.22D416C07D@po15720vm.idsi0.si.c-s.fr> <CA+7wUszKbPKu86jSprEBJsxJOmyAc42x5S4XmPce_RFXTsHTfQ@mail.gmail.com> <e49e2296-11f8-a2fa-6b64-db18ba5db641@c-s.fr> <CA+7wUswJoGnb50y8jbPfsi9ztCO1jZ+O4cirHtXc7gp7MXRm5Q@mail.gmail.com> <48cdb73c-f0c4-0c8a-19f5-8fce000e7050@c-s.fr> <CA+7wUszJzG4CyfO2_Tvmc_u9oMPxLQMaiP+HnhpEex6KCRgSYw@mail.gmail.com>
Date:   Thu, 19 Apr 2018 01:13:18 +1000
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Mathieu Malaterre <malat@debian.org> writes:
> On Wed, Apr 18, 2018 at 8:34 AM, Christophe LEROY
...
>
>> Can you also provide a copy of the messages you can see (prom_init ...) when
>> boot is ok ?
>
> Hum. I've always been interested in seeing it also myself. Is there a
> way to setup env to see those message (netconsole, delayed boot
> messages ...) ? I never found a clear documentation on how to do that
> on (closed) Apple hardware.

If you see nothing after prom_init it usually indicates the kernel died
very early in boot before it could find the console.

The only option then is to enable one of the hard-coded EARLY_DEBUG
options.

I don't know which one works on a G4, maybe CONFIG_PPC_EARLY_DEBUG_BOOTX ?

I assume it doesn't have a serial port.

cheers