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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6952BC433E0 for ; Mon, 25 May 2020 13:40:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4317A2073B for ; Mon, 25 May 2020 13:40:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390800AbgEYNk3 (ORCPT ); Mon, 25 May 2020 09:40:29 -0400 Received: from mga14.intel.com ([192.55.52.115]:32840 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388794AbgEYNk2 (ORCPT ); Mon, 25 May 2020 09:40:28 -0400 IronPort-SDR: 97YWSA+OHdIUc+yjrho8MGmUxHkCuEivFLNCaH//GJM2q1CHoXDeOESY/HrJ/p+uZkzdn81gVa gJNMcY+6azzg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 May 2020 06:40:27 -0700 IronPort-SDR: NNxlW114Pgv6T09M/uQc3/OErRaRyawJdQ2EvjhndITWCYbTuEhp8nu1cA0/hl+r5Od1Vi9gGS SI6MRzYZlYCQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,433,1583222400"; d="scan'208";a="255110394" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by orsmga007.jf.intel.com with ESMTP; 25 May 2020 06:40:25 -0700 Received: from andy by smile with local (Exim 4.93) (envelope-from ) id 1jdDLA-008nLx-58; Mon, 25 May 2020 16:40:28 +0300 Date: Mon, 25 May 2020 16:40:28 +0300 From: Andy Shevchenko To: Vladimir Oltean Cc: gregkh@linuxfoundation.org, linux-serial@vger.kernel.org, jslaby@suse.com, lukas@wunner.de, heikki.krogerus@linux.intel.com, vigneshr@ti.com, linux-kernel@vger.kernel.org, fido_max@inbox.ru, radu-andrei.bulie@nxp.com Subject: Re: [PATCH] serial: 8250: probe all 16550A variants by default Message-ID: <20200525134028.GA1634618@smile.fi.intel.com> References: <20200525130238.3614179-1-olteanv@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200525130238.3614179-1-olteanv@gmail.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 25, 2020 at 04:02:38PM +0300, Vladimir Oltean wrote: > From: Vladimir Oltean > > On NXP T1040, the UART is typically detected as 16550A_FSL64. After said > patch, it gets detected as plain 16550A and the Linux console is > completely garbled and missing characters. > > So clearly, introducing the SERIAL_8250_16550A_VARIANTS config option > has broken many existing users because it has changed the default > behavior. Restore that by adding a 'default y' to this option. Users who > care about 20 ms shorter boot time can always disable it, but stop > wasting many debugging hours for people who don't care all that much. While this sounds like a good enough fix of the regression, the proper one seems to have a separate quirk driver which avoids auto probe and uses compatible strings or whatever that board can supply. 8250_port historically has a burden of old and buggy hardware, that's why the above mentioned patch exposed that. That said, I have no objections, but had to note about possible approaches. > Fixes: dc56ecb81a0a ("serial: 8250: Support disabling mdelay-filled probes of 16550A variants") > Signed-off-by: Vladimir Oltean > --- > drivers/tty/serial/8250/Kconfig | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig > index af0688156dd0..89c7ecb55619 100644 > --- a/drivers/tty/serial/8250/Kconfig > +++ b/drivers/tty/serial/8250/Kconfig > @@ -63,6 +63,7 @@ config SERIAL_8250_PNP > config SERIAL_8250_16550A_VARIANTS > bool "Support for variants of the 16550A serial port" > depends on SERIAL_8250 > + default y > help > The 8250 driver can probe for many variants of the venerable 16550A > serial port. Doing so takes additional time at boot. > -- > 2.25.1 > -- With Best Regards, Andy Shevchenko