linux-kernel - Re: [PATCH] powerpc/crash: Allow direct printing on kexec

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Message-ID: <847ca1fxod.fsf@jogness.linutronix.de>
Date: Mon, 21 Oct 2024 14:33:46 +0206
From: John Ogness <john.ogness@...utronix.de>
To: Ryo Takakura <ryotkkr98@...il.com>
Cc: christophe.leroy@...roup.eu, hbathini@...ux.ibm.com,
 leobras.c@...il.com, linux-kernel@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, maddy@...ux.ibm.com, mpe@...erman.id.au,
 naveen@...nel.org, npiggin@...il.com, pmladek@...e.com,
 ryotkkr98@...il.com, sourabhjain@...ux.ibm.com
Subject: Re: [PATCH] powerpc/crash: Allow direct printing on kexec

On 2024-10-21, Ryo Takakura <ryotkkr98@...il.com> wrote:
>> Rather than removing the deferring, it would be better to convert the
>> console you are using to the new NBCON API. Then it would be able to
>> print direct and safe during panic. (printk_deferred does not affect
>> NBCON consoles.) What console driver are you using that you want to
>> see the messages on?
>
> I was working on qemu ppc64 this time but I am usually working on 
> Raspberry Pi 4 (mostly for fun and study) which uses either of 
> bcm2835-aux-uart or amba-pl011. It would be really nice to see them 
> working as nbcon!
> I am thinking of taking a look at [0] but If there were any other 
> references, I would really like to look into as well.
>
> [0] https://lore.kernel.org/lkml/87wn3zsz5x.fsf@jogness.linutronix.de/

The lastest version of the series is here [1]. The series is still
undergoing revisions, however the changes are 8250-specific. The API for
nbcon consoles is already available since 6.12-rc1. You are certainly
welcome to try to convert one of those Raspi 4 drivers to the nbcon
interface. I would be happy to review it.

John Ogness

[1] https://lore.kernel.org/lkml/20240913140538.221708-1-john.ogness@linutronix.de