From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E4DEEC61DA3 for ; Tue, 21 Feb 2023 16:13:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233461AbjBUQNq (ORCPT ); Tue, 21 Feb 2023 11:13:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38982 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233278AbjBUQNp (ORCPT ); Tue, 21 Feb 2023 11:13:45 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3C51872BD for ; Tue, 21 Feb 2023 08:13:44 -0800 (PST) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1676996022; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kHE4CjoVvckPZ8RZhCZC1//cOZCPRjfjAu6DZzurUTE=; b=JZtplFEOIA73U5/WnWPs1eLHCy0E2zXmzrCwf04vSce4/lSkJxrzxTQT/jrVc/aodultK0 Q6euBYDCYSVKlzma7jh/2ENkOBJrelHjKb4U2Y8BROQFWkXgjPFltNXm9izxwNAdDKVyFO PaGHEAc+PLuxdpg2SRhJ+YSLZGwUa5fKgbKSiCy9zxOTPYkDlZ6YsLNh5yRr67O9J+S/QS sooZEZ8za1cCBvHJ9gBeau2cO+hjPzwF4v3bZ/PlD3vsVa78cXohiGWrpyRDumOCsPiCAn MotPavnJ+g14LWjUnxdfNg4CW3bPEacpOFy740g/NNsBhTM+S4e/iaZnMjcJlA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1676996022; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kHE4CjoVvckPZ8RZhCZC1//cOZCPRjfjAu6DZzurUTE=; b=RVjH4YZl+Sp8ls2mQuLWu0Ur/e+po3hVmYv9/XYxRfy9Fe70O8A7V7MX8mx0U811LHylP1 Tsm6ewUvWTynLhCQ== To: =?utf-8?Q?Andr=C3=A9?= Pribil , "linux-rt-users@vger.kernel.org" Subject: Re: printk: console output corrupted In-Reply-To: References: Date: Tue, 21 Feb 2023 17:18:24 +0106 Message-ID: <87bklnro9j.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org Hi Andre, On 2023-02-21, Andr=C3=A9 Pribil 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=3D1" 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