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=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 41660C4332B for ; Mon, 23 Mar 2020 10:51:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 057C82076A for ; Mon, 23 Mar 2020 10:51:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="bdVyJBL3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728079AbgCWKu7 (ORCPT ); Mon, 23 Mar 2020 06:50:59 -0400 Received: from mail-lj1-f193.google.com ([209.85.208.193]:37321 "EHLO mail-lj1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727874AbgCWKu6 (ORCPT ); Mon, 23 Mar 2020 06:50:58 -0400 Received: by mail-lj1-f193.google.com with SMTP id r24so14023402ljd.4 for ; Mon, 23 Mar 2020 03:50:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=h9tNy9xYbDdOC07CHf7H4ZkCbKHWeUnDdMW9CfCVCkY=; b=bdVyJBL359733WGvtU7Gof3j1/tutWr7jojcWw8wXUmNPOuLG7Hr563TWG8poB1U5U xUVWVNWAz8/ChLwTngd8zi2Cfb9DT1RmMpNDrqfdF6H5cXf35C+3gOGZpsoMGME2J3Mp JhUavNjXK2+gC4dHuct1aCXROrYOZEmKTFMPbSbRRfhPY/erbp78N+kosI7kczs0+Qml f56C0Icn43kk4UuuvObeRpH0ScxZsCHIfXWWycdaKJ1jNTfl8L24YBeXH9Vi2a3ZIV96 N/xbr5/YMVNbX4HF5inRVM+Y0mkGUdcThY7SG9mi2CVHP/tjw3uDD9J9Buv8gnisr/pV kATQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=h9tNy9xYbDdOC07CHf7H4ZkCbKHWeUnDdMW9CfCVCkY=; b=LNxeMypAAB05/kxUuoEs/Wya4ruCvtlM1+NPLs3GJJjE+tKKBMCUMJ3ZbjZV4y8/16 vi0fr8Zy8d33zS4VzD+9oR+IYbWZOaeXEu8NlQC3DbsQay0NRAbYyV3N1EZmWhSEB7R+ 9MsW69bu+kx9OHxQXDW12jCAAu6sEwuteNWI1MRMwBMEaAfvCiP137o0MVf2SwF66GxR 5r7+UFVikOBgUTkN0oi+fBzBGdIg9ImbndWAW+SLnsZfHBhAOX/OHKBFCfTe4s3i816E mmqCCRW7mL6n6j2kfeBXJhKboJtgFBl3jo6uxy84CBavGHEDgXh7QunJuCNkTXHPJoqH kQbQ== X-Gm-Message-State: ANhLgQ1TIitE9EU41nGFTD1itFGOWNNc4UXdQ2i146FPAhuDtD2sWNPo 1dGJ15woTSxksBiWgxKuSpQ= X-Google-Smtp-Source: ADFU+vsKiSgepWD3zBk0d7FCKh222LKCe+KoUW/BqEQdIfjFcQps3p3ZMq9+T5sKfUjBP3ucTMZcwg== X-Received: by 2002:a2e:b896:: with SMTP id r22mr9541559ljp.43.1584960655907; Mon, 23 Mar 2020 03:50:55 -0700 (PDT) Received: from [192.168.0.74] ([178.233.178.9]) by smtp.gmail.com with ESMTPSA id h25sm8240959ljg.31.2020.03.23.03.50.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Mar 2020 03:50:55 -0700 (PDT) Subject: [RFC PATCH 3/3] printk: Preset tty0 as a pseudo-preferred console To: Greg Kroah-Hartman , Jiri Slaby , Petr Mladek , Sergey Senozhatsky Cc: Steven Rostedt , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <44156595-0eee-58da-4376-fd25b634d21b@gmail.com> From: Alper Nebi Yasak Message-ID: <2d6ab3dc-3571-2d27-b763-84c21e38ae2e@gmail.com> Date: Mon, 23 Mar 2020 13:50:49 +0300 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <44156595-0eee-58da-4376-fd25b634d21b@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The ACPI SPCR (Serial Port Console Redirection) table from a machine's firmware can specify a serial console which can be used for earlycon. However, in at least ARM64 systems the same device is also set up as the preferred console. Presumably due to the order of acpi_parse_spcr and VT's register_device calls, setting the specified console as the preferred one can prevent registering VT as a console. This might look appropriate for machines which do not have or need working graphics and whose users most likely have access to a serial port. However, the use of SPCR tables may not be limited these. For example, ARM64 QEMU virtual machines include a SPCR table regardless of the existence of a graphics output or even the nonexistence of a serial console. Or server hardware which has a SPCR table can be repurposed into a workstation with the addition of a graphics card. As a result, boot messages and early userspace prompts can go to an unexpected console. This patch presets tty0 as a pseudo-preferred console at compile-time to ensure that CONFIG_VT_CONSOLE always results in the VT console getting registered. With this, VT can get registered, these other consoles are preferred when VT is a dummy, but we can also bump up VTs preference when working graphics are available. Without this patch, an ARM64 QEMU virtual machine has roughly the following order of console events and consoles: $ sudo dmesg | grep -i "console\|printk" [ 0.000000] ACPI: SPCR: console: pl011,mmio,0x9000000,9600 [ 0.000000] printk: bootconsole [pl11] enabled [ 0.004890] Console: colour dummy device 80x25 [ 0.412252] printk: console [ttyAMA0] enabled [ 0.416173] printk: bootconsole [pl11] disabled [ 3.940510] Console: switching to colour frame buffer device 128x48 $ cat /proc/consoles ttyAMA0 -W- (EC a) 204:64 In addition, boot messages aren't printed to the framebuffer (as tty0 is not registered). With this patch, boot messages are visible on the framebuffer and the information above becomes: $ sudo dmesg | grep -i "console\|printk" [ 0.000000] ACPI: SPCR: console: pl011,mmio,0x9000000,9600 [ 0.000000] printk: bootconsole [pl11] enabled [ 0.002768] Console: colour dummy device 80x25 [ 0.004371] printk: console [tty0] enabled [ 0.380166] printk: console [ttyAMA0] enabled [ 0.387337] printk: bootconsole [pl11] disabled [ 4.695030] Console: switching to colour frame buffer device 128x48 [ 4.709759] printk: switching to console [tty0] $ cat /proc/consoles tty0 -WU (EC p ) 4:7 ttyAMA0 -W- (E a) 204:64 Signed-off-by: Alper Nebi Yasak --- kernel/printk/printk.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 6b16c973587..4b05779ab69 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -277,7 +277,19 @@ static struct console *exclusive_console; #define MAX_CMDLINECONSOLES 8 +/* + * The preferred_console and has_preferred_console variables are + * intentionally not modified to reflect this so that the first + * registered console is still used as the preferred console. + */ +#ifdef CONFIG_VT_CONSOLE +static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES] = { + [0].name = "tty", + [0].index = 0, +}; +#elif static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; +#endif static int preferred_console = -1; static bool has_preferred_console; -- 2.26.0.rc2