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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1,WEIRD_QUOTING 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 0F90EECE58D for ; Wed, 9 Oct 2019 14:40:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D90F920640 for ; Wed, 9 Oct 2019 14:40:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731544AbfJIOkD (ORCPT ); Wed, 9 Oct 2019 10:40:03 -0400 Received: from foss.arm.com ([217.140.110.172]:35802 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729491AbfJIOkD (ORCPT ); Wed, 9 Oct 2019 10:40:03 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id ACEA1337; Wed, 9 Oct 2019 07:40:02 -0700 (PDT) Received: from [10.1.197.57] (e110467-lin.cambridge.arm.com [10.1.197.57]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 725A43F71A; Wed, 9 Oct 2019 07:40:01 -0700 (PDT) Subject: Re: [PATCH] dts: Disable DMA support on the BK4 vf610 device's fsl_lpuart driver To: Lukasz Majewski , linux-kernel@vger.kernel.org, Shawn Guo Cc: Mark Rutland , devicetree@vger.kernel.org, Sascha Hauer , Stefan Agner , Rob Herring , Pengutronix Kernel Team , linux-arm-kernel@lists.infradead.org References: <20191009143032.9261-1-lukma@denx.de> From: Robin Murphy Message-ID: Date: Wed, 9 Oct 2019 15:40:00 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20191009143032.9261-1-lukma@denx.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/10/2019 15:30, Lukasz Majewski wrote: > This change disables the DMA support (RX/TX) on the NXP's fsl_lpuart > driver - the PIO mode is used instead. This change is necessary for better > robustness of BK4's device use cases with many potentially interrupted > short serial transfers. > > Without it the driver hangs when some distortion happens on UART lines. > > Signed-off-by: Lukasz Majewski > --- > arch/arm/boot/dts/vf610-bk4.dts | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/arm/boot/dts/vf610-bk4.dts b/arch/arm/boot/dts/vf610-bk4.dts > index 0f3870d3b099..ad20f3442d40 100644 > --- a/arch/arm/boot/dts/vf610-bk4.dts > +++ b/arch/arm/boot/dts/vf610-bk4.dts > @@ -259,24 +259,28 @@ > &uart0 { > pinctrl-names = "default"; > pinctrl-0 = <&pinctrl_uart0>; > + dma-names = "",""; This looks like a horrible hack - is there any reason not to just strip things at compile-time, i.e. "/delete-property/ dmas;"? Robin. > status = "okay"; > }; > > &uart1 { > pinctrl-names = "default"; > pinctrl-0 = <&pinctrl_uart1>; > + dma-names = "",""; > status = "okay"; > }; > > &uart2 { > pinctrl-names = "default"; > pinctrl-0 = <&pinctrl_uart2>; > + dma-names = "",""; > status = "okay"; > }; > > &uart3 { > pinctrl-names = "default"; > pinctrl-0 = <&pinctrl_uart3>; > + dma-names = "",""; > status = "okay"; > }; > >