Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932280AbcKGP0m (ORCPT ); Mon, 7 Nov 2016 10:26:42 -0500 Received: from mail-it0-f68.google.com ([209.85.214.68]:34976 "EHLO mail-it0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753029AbcKGP0k (ORCPT ); Mon, 7 Nov 2016 10:26:40 -0500 Subject: Re: [PATCH v3] console: use first console if stdout-path device doesn't appear To: Paul Burton , Michael Ellerman References: <2c67e39b-fc33-918a-774e-d9238e837c03@lwfinger.net> <20161103125758.3415-1-paul.burton@imgtec.com> <8737j3n18r.fsf@concordia.ellerman.id.au> <13471233.iqSeGS5aQ3@np-p-burton> Cc: Sergey Senozhatsky , Andreas Schwab , Andrew Morton , Borislav Petkov , Petr Mladek , Tejun Heo , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org From: Larry Finger Message-ID: <4f990791-ebff-dbe3-b923-3cac5fd6f97d@lwfinger.net> Date: Mon, 7 Nov 2016 09:26:37 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <13471233.iqSeGS5aQ3@np-p-burton> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2004 Lines: 48 On 11/07/2016 03:18 AM, Paul Burton wrote: > On Monday, 7 November 2016 19:27:32 GMT Michael Ellerman wrote: >> Paul Burton writes: >>> If a device tree specified a preferred device for kernel console output >>> via the stdout-path or linux,stdout-path chosen node properties there's >>> no guarantee that it will have specified a device for which we have a >>> driver. It may also be the case that we do have a driver but it doesn't >>> call of_console_check() to register as a preferred console (eg. offb >>> driver as used on powermac systems). >>> >>> In these cases try to ensure that we provide some console output by >>> enabling the first usable registered console, which we keep track of >>> with the of_fallback_console variable. Affected systems will enable >>> their console later than they did prior to commit 05fd007e4629 >>> ("console: don't prefer first registered if DT specifies stdout-path") >>> but should otherwise produce the same output. >>> >>> Tested in QEMU with a PowerPC pseries_defconfig kernel. >> >> Hi Paul, >> >> This does "work", as in it boots and I get a console. But the delay in >> getting output on the VGA is not workable. I get pretty much no output >> until the machine is booted entirely to userspace, meaning any crash >> prior to that will be undebuggable. >> >> I also note Andreas reports it doesn't work at all on PowerMac. >> >> Please send a revert and we can try again next cycle. >> >> cheers > > Hi Michael, > > A revert was already submitted by Hans de Goede & is being discussed over > here: > > https://marc.info/?l=linux-kernel&m=147826151427455&w=2 I am a little surprised that I was not CCd on that thread. To reiterate, my PowerBook G4 with a PPC32 processor CRASHES on boot. That is a lot more serious than the console output disappearing. As it seems unlikely that this regression will be fixed in the current cycle, I recommend that the reversion of commit 05fd007e4629 until a proper fix is available. Larry