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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 09038C04AB4 for ; Wed, 15 May 2019 03:29:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D866A20862 for ; Wed, 15 May 2019 03:29:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726254AbfEOD3y (ORCPT ); Tue, 14 May 2019 23:29:54 -0400 Received: from relay1.mentorg.com ([192.94.38.131]:61222 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726201AbfEOD3y (ORCPT ); Tue, 14 May 2019 23:29:54 -0400 Received: from svr-orw-mbx-01.mgc.mentorg.com ([147.34.90.201]) by relay1.mentorg.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-SHA384:256) id 1hQkbw-0006UV-Ol from George_Davis@mentor.com ; Tue, 14 May 2019 20:29:44 -0700 Received: from localhost (147.34.91.1) by svr-orw-mbx-01.mgc.mentorg.com (147.34.90.201) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Tue, 14 May 2019 20:29:42 -0700 From: "George G. Davis" To: Eugeniu Rosca , Geert Uytterhoeven , Simon Horman , Wolfram Sang , Greg Kroah-Hartman , Jiri Slaby , "open list:SERIAL DRIVERS" , open list CC: Chris Brandt , Ulrich Hecht , Andy Lowe , Linux-Renesas , OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS , Magnus Damm , Rob Herring , Mark Rutland , "George G. Davis" , Subject: [PATCH v3] serial: sh-sci: disable DMA for uart_console Date: Tue, 14 May 2019 23:29:34 -0400 Message-ID: <1557890974-21179-1-git-send-email-george_davis@mentor.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain X-ClientProxiedBy: SVR-ORW-MBX-09.mgc.mentorg.com (147.34.90.209) To svr-orw-mbx-01.mgc.mentorg.com (147.34.90.201) Sender: linux-renesas-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-renesas-soc@vger.kernel.org As noted in commit 84b40e3b57ee ("serial: 8250: omap: Disable DMA for console UART"), UART console lines use low-level PIO only access functions which will conflict with use of the line when DMA is enabled, e.g. when the console line is also used for systemd messages. So disable DMA support for UART console lines. Reported-by: Michael Rodin Link: https://patchwork.kernel.org/patch/10929511/ Tested-by: Eugeniu Rosca Reviewed-by: Simon Horman Reviewed-by: Wolfram Sang Reviewed-by: Geert Uytterhoeven Cc: stable@vger.kernel.org Signed-off-by: George G. Davis --- v2: Clarify comment regarding DMA support on kernel console, add {Tested,Reviewed}-by:, and Cc: linux-stable lines. v3: Change Fixes: reference to Link: reference and add another Reviewed-by. --- drivers/tty/serial/sh-sci.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index 3cd139752d3f..abc705716aa0 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -1557,6 +1557,13 @@ static void sci_request_dma(struct uart_port *port) dev_dbg(port->dev, "%s: port %d\n", __func__, port->line); + /* + * DMA on console may interfere with Kernel log messages which use + * plain putchar(). So, simply don't use it with a console. + */ + if (uart_console(port)) + return; + if (!port->dev->of_node) return; -- 2.7.4