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From: "André Pribil" <Andre.Pribil@hms-networks.com>
To: "linux-rt-users@vger.kernel.org" <linux-rt-users@vger.kernel.org>
Cc: John Ogness <john.ogness@linutronix.de>
Subject: printk: console output corrupted
Date: Tue, 21 Feb 2023 12:38:20 +0000	[thread overview]
Message-ID: <AM5PR10MB162013648CCFDDDC4EE42A3CBDA59@AM5PR10MB1620.EURPRD10.PROD.OUTLOOK.COM> (raw)

Hi,

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?

I don't know how to further trace this. Any help is appreciated.

Thanks,
Andre



             reply	other threads:[~2023-02-21 12:38 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-21 12:38 André Pribil [this message]
2023-02-21 16:12 ` printk: console output corrupted John Ogness
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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