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 E766EC433EF for ; Sat, 4 Jun 2022 09:04:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233780AbiFDJED (ORCPT ); Sat, 4 Jun 2022 05:04:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50148 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230287AbiFDJEB (ORCPT ); Sat, 4 Jun 2022 05:04:01 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B643A2CCB8; Sat, 4 Jun 2022 02:03:57 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 22C95B80123; Sat, 4 Jun 2022 09:03:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40071C34115; Sat, 4 Jun 2022 09:03:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1654333434; bh=217ze+lr6QqzxW0zfUNP8dEz4eFku6hxMpaH4iUZ9Zw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=M9/aU3+Ihkq6BKPt54tPmidePYdBEAe5KqSbdYG1gnO3uH/S9Dvlc5EnZzOCcicYS gpK3daMFqzKanhb5RrN53vH8FCzP2Vgw0X7FKrbUEBNM2PBvFp8sh9pmg6XwY/RWZY tvrD5gVupRmSGFp97H5OTtocNm49T4rVssrfRzKo= Date: Sat, 4 Jun 2022 11:04:30 +0200 From: Greg KH To: Paul Menzel Cc: linux-serial@vger.kernel.org, LKML Subject: Re: Non-working serial console Message-ID: References: <1880b7a7-2353-c381-5afb-1d4224eb223b@molgen.mpg.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1880b7a7-2353-c381-5afb-1d4224eb223b@molgen.mpg.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 02, 2022 at 11:09:15PM +0200, Paul Menzel wrote: > Dear Linux folks, > > > Am 02.06.22 um 18:50 schrieb Paul Menzel: > > > Since a while I noticed, output to the serial console with > > `console=ttyS0,115200n8` does not work with the attached configuration > > `defconfig-non-working-serial.txt` created by `make savedefconfig`. > > Only, when with `earlyprintk=ttyS0,115200,keep` the serial console > > starts working. I am able to reproduce it in QEMU. It’s reproducible > > with Linus’ latest master branch. > > > >     $ git log --oneline --no-decorate -1 > >     8ab2afa23bd19 Merge tag 'for-5.19/fbdev-1' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/linux-fbdev > >     $ qemu-system-x86_64 --version > >     QEMU emulator version 5.1.0 > >     Copyright (c) 2003-2020 Fabrice Bellard and the QEMU Project developers > >     $ qemu-system-x86_64 -kernel arch/x86/boot/bzImage -append "console=ttyS0,115200n8" -serial file:/dev/shm/kernel.txt -curses > > > > With `earlyprintk=` it works: > > > >     $ qemu-system-x86_64 -kernel arch/x86/boot/bzImage -append "earlyprintk=serial console=ttyS0,115200n8" -serial file:/dev/shm/kernel.txt -curses > > > > Strangely, I found a different configuration, where it works, but I > > didn’t see what configuration option makes the difference. > > > > Can you reproduce the problem with `defconfig-no-working-serial.txt`? > > It turns out, the non-working configuration build the serial 8250 driver as > a module (`CONFIG_SERIAL_8250=m`) instead of building it into the Linux > kernel. Building it into the Linux kernel and using > `CONFIG_SERIAL_8250_CONSOLE=y` fixes my issue. That makes sense, you need the console to be able to properly send data out to it :) Was this a Kconfig change somewhere recently that we messed up the defaults for? Any chance you can use 'git bisect' to track down the offending change? thanks, greg k-h