From: John Ogness <john.ogness@linutronix.de>
To: "André Pribil" <Andre.Pribil@hms-networks.com>,
"linux-rt-users@vger.kernel.org" <linux-rt-users@vger.kernel.org>
Subject: Re: printk: console output corrupted
Date: Tue, 21 Feb 2023 17:18:24 +0106 [thread overview]
Message-ID: <87bklnro9j.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <AM5PR10MB162013648CCFDDDC4EE42A3CBDA59@AM5PR10MB1620.EURPRD10.PROD.OUTLOOK.COM>
Hi Andre,
On 2023-02-21, André Pribil <Andre.Pribil@hms-networks.com> wrote:
> I'm using a IMX8MP board with kernel 5.10.165-rt81. UART3 is used as
> the console device. When the device boots the serial outputs on this
> UART get corrupted at some point. It looks like only one line is
> corrupted. However, this line often confuses my terminal, so that the
> lines behind are also not shown correctly. A reset of the terminal
> fixes that.
>
> I could not figure out why this happens, yet. I only know that the
> issue does not occur when I remove the preempt-rt patch or when I
> specify the "maxcpus=1" kernel command line parameter. I also tried to
> enable/disable the "earlycon" setting, but this seem to only change
> the time when this happens during the boot messages.
>
> When the boot messages are afterwards displayed with "dmesg", they do
> not contain corrupted characters. Therefore, I assume that the
> corruption occurs at the UART level. Maybe some lock issue and
> therefore some concurrent access to the UART registers?
There is a known problem [0] with this printk implementation that it
does not support boot consoles. I will follow-up this email with the
rebased patch from Petr Mladek, which should work around the
issue. Please check if it works for you.
John Ogness
[0] https://lore.kernel.org/lkml/YrCO04oNncE1xF5K@alley
next prev parent reply other threads:[~2023-02-21 16:13 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-21 12:38 printk: console output corrupted André Pribil
2023-02-21 16:12 ` John Ogness [this message]
2023-02-21 16:15 ` [PATCH] printk/console: Enable console kthreads only when there is no boot console left John Ogness
2023-02-22 10:53 ` André Pribil
2023-02-22 14:35 ` André Pribil
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