From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752835AbcCDLyP (ORCPT ); Fri, 4 Mar 2016 06:54:15 -0500 Received: from mail-lb0-f169.google.com ([209.85.217.169]:35598 "EHLO mail-lb0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750966AbcCDLyN (ORCPT ); Fri, 4 Mar 2016 06:54:13 -0500 Subject: Re: [PATCH v4 0/4] ACPI: parse the SPCR table To: Peter Hurley , Aleksey Makarov , linux-acpi@vger.kernel.org References: <1456747355-15692-1-git-send-email-aleksey.makarov@linaro.org> <56D5B5CB.7010702@hurleysoftware.com> <56D8272E.20705@gmail.com> <56D859CC.7010901@hurleysoftware.com> Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Russell King , Greg Kroah-Hartman , "Rafael J . Wysocki" , Leif Lindholm , Graeme Gregory , Al Stone , Christopher Covington , Yury Norov , "Zheng, Lv" From: Aleksey Makarov Message-ID: <56D9772B.5000402@linaro.org> Date: Fri, 4 Mar 2016 14:53:15 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <56D859CC.7010901@hurleysoftware.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/03/2016 06:35 PM, Peter Hurley wrote: > On 03/03/2016 03:59 AM, Aleksey Makarov wrote: >> >> >> On 03/01/2016 06:31 PM, Peter Hurley wrote: >>> On 02/29/2016 04:02 AM, Aleksey Makarov wrote: >>>> 'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port >>>> Console Redirection Table) [2] as a mandatory ACPI table that >>>> specifies the configuration of serial console. >>>> >>>> Introduce a new function acpi_console_check(). At the uart port >>>> registration, this function checks if the ACPI SPCR table specifies >>>> its argument of type struct uart_port to be a console >>>> and if so calls add_preferred_console(). >>> >>> How will a user enable an earlycon on the same console as the SPCR >>> console if there is no DBG2 table? >> >> ... >> [ 0.000000] earlycon: pl11 at MMIO 0x0000000009000000 (options '') >> [ 0.000000] bootconsole [pl11] enabled >> ... >> [ 0.000000] Kernel command line: root=/dev/vda1 rw systemd.show_status=no acpi=force earlycon=pl011,0x9000000 >> ... >> [ 0.318248] ACPI: SPCR: adding preferred console [ttyAMA0] >> [ 0.318736] ARMH0011:00: ttyAMA0 at MMIO 0x9000000 (irq = 5, base_baud = 0) is a SBSA >> [ 0.319502] console [ttyAMA0] enabled >> [ 0.319502] console [ttyAMA0] enabled >> [ 0.319933] bootconsole [pl11] disabled >> [ 0.319933] bootconsole [pl11] disabled >> ... >> >> Why? > > That's pretty disingenuous; via command line? > > By that measure, none of your patches are required because a user > can already start both console and earlycon without them. > > With the console location specified in the SPCR, earlycon should > be opt-in on the command-line simply with "earlycon" command-line > parameter. Yes. That's why we have SPCR *and* DBG2. DBG2 specifies where we should run earlycon. >>> How will a user enable an earlycon on the same console as the SPCR >>> console if there is no DBG2 table? In no way. You need DBG2 to run earlycon. (If you don't want to specify it's address etc explicitly)