From patchwork Mon May 13 15:47:26 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "George G. Davis" X-Patchwork-Id: 10941331 X-Patchwork-Delegate: geert@linux-m68k.org Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 465BD1395 for ; Mon, 13 May 2019 15:48:23 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 37F5E1FF13 for ; Mon, 13 May 2019 15:48:23 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 295C0283F9; Mon, 13 May 2019 15:48:23 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A7F631FF13 for ; Mon, 13 May 2019 15:48:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728409AbfEMPsW (ORCPT ); Mon, 13 May 2019 11:48:22 -0400 Received: from relay1.mentorg.com ([192.94.38.131]:37325 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726814AbfEMPsW (ORCPT ); Mon, 13 May 2019 11:48:22 -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 1hQDBb-00024C-CH from George_Davis@mentor.com ; Mon, 13 May 2019 08:48:19 -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; Mon, 13 May 2019 08:48:17 -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 v2] serial: sh-sci: disable DMA for uart_console Date: Mon, 13 May 2019 11:47:26 -0400 Message-ID: <1557762446-23811-1-git-send-email-george_davis@mentor.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 X-ClientProxiedBy: svr-orw-mbx-02.mgc.mentorg.com (147.34.90.202) 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 X-Virus-Scanned: ClamAV using ClamSMTP 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. Fixes: https://patchwork.kernel.org/patch/10929511/ Reported-by: Michael Rodin Tested-by: Eugeniu Rosca Reviewed-by: Simon Horman Reviewed-by: Wolfram Sang Cc: stable@vger.kernel.org Signed-off-by: George G. Davis Reviewed-by: Geert Uytterhoeven --- v2: Clarify comment regarding DMA support on kernel console, add {Tested,Reviewed}-by:, and Cc: linux-stable lines. --- 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;