From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751804AbcBHLut (ORCPT ); Mon, 8 Feb 2016 06:50:49 -0500 Received: from mx2.suse.de ([195.135.220.15]:54139 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750844AbcBHLur (ORCPT ); Mon, 8 Feb 2016 06:50:47 -0500 Subject: Re: [PATCH] tty: serial: meson: Implement earlycon support To: Peter Hurley References: <1454878635-24396-1-git-send-email-afaerber@suse.de> <56B817FC.4000604@hurleysoftware.com> Cc: linux-arm-kernel@lists.infradead.org, Carlo Caione , Jonathan Corbet , Greg Kroah-Hartman , Jiri Slaby , linux-doc , LKML , linux-serial , linux-meson@googlegroups.com, Matthias Brugger , Nicolas Saenz From: =?UTF-8?Q?Andreas_F=c3=a4rber?= X-Enigmail-Draft-Status: N1110 Organization: SUSE Linux GmbH Message-ID: <56B88113.2050800@suse.de> Date: Mon, 8 Feb 2016 12:50:43 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <56B817FC.4000604@hurleysoftware.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, Am 08.02.2016 um 05:22 schrieb Peter Hurley: > On 02/07/2016 12:57 PM, Andreas Färber wrote: >> Reuse the existing console write implementation for implementing >> DT-based and command-line-based earlycon support. >> >> Signed-off-by: Andreas Färber >> --- >> Documentation/kernel-parameters.txt | 6 ++++++ >> drivers/tty/serial/meson_uart.c | 13 +++++++++++++ >> 2 files changed, 19 insertions(+) >> >> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt >> index 602065c..90801ac 100644 >> --- a/Documentation/kernel-parameters.txt >> +++ b/Documentation/kernel-parameters.txt >> @@ -1030,6 +1030,12 @@ Such letter suffixes can also be entirely omitted. >> the driver will use only 32-bit accessors to read/write >> the device registers. >> >> + meson_serial, >> + Start an early, polled-mode console on a meson serial >> + port at the specified address. The serial port must >> + already be setup and configured. Options are not yet >> + supported. >> + >> msm_serial, >> Start an early, polled-mode console on an msm serial >> port at the specified address. The serial port >> diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c >> index b12a37b..6f89567 100644 >> --- a/drivers/tty/serial/meson_uart.c >> +++ b/drivers/tty/serial/meson_uart.c >> @@ -548,6 +548,19 @@ static int __init meson_serial_console_init(void) >> } >> console_initcall(meson_serial_console_init); >> >> +static int __init >> +meson_serial_early_console_setup(struct earlycon_device *device, const char *opt) >> +{ >> + if (!device->port.membase) >> + return -ENODEV; >> + >> + device->con->write = meson_serial_console_write; > > meson_serial_console_write() is not appropriate for earlycon; it assumes the > earlycon port is the same as the driver port (it isn't). Thanks for spotting that. I forgot to mention that I tested this on arm64, where there is no earlyprintk any more, seemingly successfully getting a bootconsole uart0. Using co->data instead of co->index I now get meson_serial0 instead, doh. This probably slipped though because another patch is necessary for fixing the baudrate calculation on my device. >> + return 0; >> +} >> +EARLYCON_DECLARE(meson_serial, meson_serial_early_console_setup); >> +OF_EARLYCON_DECLARE(meson_serial, "amlogic,meson-uart", >> + meson_serial_early_console_setup); > > With today's linux-next (or Greg's tty-next tree), it is no longer necessary to > declare separate earlycon's when you want both; OF_EARLYCON_DECLARE() declares > both a devicetree-enabled earlycon and automatically provides for a command line > earlycon of the same name. Thanks for the hint, it was based on linux-next from a couple days ago. Is there any guidance wrt naming? I noticed that msm uses -uart in the compatible string and _serial for earlycon, so I copied that; should it rather be meson_uart or just meson? Regards, Andreas -- SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Felix Imendörffer, Jane Smithard, Graham Norton; HRB 21284 (AG Nürnberg)