From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760261AbcKDMLp (ORCPT ); Fri, 4 Nov 2016 08:11:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53140 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753449AbcKDMLn (ORCPT ); Fri, 4 Nov 2016 08:11:43 -0400 From: Hans de Goede To: Linus Torvalds , Andrew Morton , Paul Burton , Rob Herring , Frank Rowand , Thorsten Leemhuis Cc: Greg Kroah-Hartman , Tejun Heo , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [REGRESSION] "console: don't prefer first registered if DT specifies stdout-path" breaks console on video outputs of various ARM boards Date: Fri, 4 Nov 2016 13:11:34 +0100 Message-Id: <20161104121135.4780-1-hdegoede@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Fri, 04 Nov 2016 12:11:42 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi All, While booting 4.9-rc# for the first time on an Allwinner A33 tablet, I noticed that after u-boot the LCD display stayed black. It turns out that there was an issue which caused X to never get up, and all kernel (and other startup) messages prior to that only went to ttyS0 which consists of 2 tiny testpads on the PCB with this tablet. The same issue will also happen on any ARM boards which have a HDMI or composite video output and which use a stdout-path pointing to their serial console. I think this will e.g. also impact the Raspberry Pi, I know for certain that this will impact the 99 different Allwinnner boards currently supported by mainline u-boot + the mainline kernel. This is a behavior changes from previous kernels and I consider this a regression. Thus I propose to revert the commit in question, for more info here is a partial copy of the commit message of the proposed revert: The reverted commit changes existing behavior on which many ARM boards rely. Many ARM small-board-computers, like e.g. the Raspberry Pi have both a video output and a serial console. Depending on whether the user is using the device as a more regular computer; or as a headless device we need to have the console on either one or the other. Many users rely on the kernel behavior of the console being present on both outputs, before the reverted commit the console setup with no console= kernel arguments on an ARM board which sets stdout-path in dt would look like this: [root@localhost ~]# cat /proc/consoles ttyS0 -W- (EC p a) 4:64 tty0 -WU (E p ) 4:1 Where as after the reverted commit, it looks like this: [root@localhost ~]# cat /proc/consoles ttyS0 -W- (EC p a) 4:64 This commit reverts commit 05fd007e4629 ("console: don't prefer first registered if DT specifies stdout-path") restoring the original behavior. Regards, Hans