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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 23341C2D0EC for ; Mon, 30 Mar 2020 14:56:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EEDE32073B for ; Mon, 30 Mar 2020 14:56:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728881AbgC3O4q (ORCPT ); Mon, 30 Mar 2020 10:56:46 -0400 Received: from mga17.intel.com ([192.55.52.151]:7882 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728465AbgC3O4q (ORCPT ); Mon, 30 Mar 2020 10:56:46 -0400 IronPort-SDR: rkZn9l1//fdEx+uNXJoiJ0ZFrdEk6SkG9Q/CyFSV0SvvvBIepSMWzHrxuYJcyePM8jasVza/23 knMwkfiol0GA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Mar 2020 07:56:45 -0700 IronPort-SDR: edpFT0HIsEHMg/tLPRba1KhN2kNU/6sO0pnJBSTuDdi1YcvX5l4mugCCOZrI3uXuNCbo0U31Kp kNFvCspetNdg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,324,1580803200"; d="scan'208";a="239833481" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by fmsmga007.fm.intel.com with ESMTP; 30 Mar 2020 07:56:43 -0700 Received: from andy by smile with local (Exim 4.93) (envelope-from ) id 1jIvqH-00EEa1-Gd; Mon, 30 Mar 2020 17:56:45 +0300 Date: Mon, 30 Mar 2020 17:56:45 +0300 From: Andy Shevchenko To: Heiko Stuebner Cc: gregkh@linuxfoundation.org, jslaby@suse.com, matwey.kornilov@gmail.com, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, lukas@wunner.de, christoph.muellner@theobroma-systems.com, giulio.benetti@micronovasrl.com, Heiko Stuebner Subject: Re: [PATCH v2 6/7] serial: 8250: Support separate rs485 rx-enable GPIO Message-ID: <20200330145645.GX1922688@smile.fi.intel.com> References: <20200325231422.1502366-1-heiko@sntech.de> <20200325231422.1502366-7-heiko@sntech.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200325231422.1502366-7-heiko@sntech.de> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 26, 2020 at 12:14:21AM +0100, Heiko Stuebner wrote: > From: Heiko Stuebner > > The RE signal is used to control the duplex mode of transmissions, > aka receiving data while sending in full duplex mode, while stopping > receiving data in half-duplex mode. > > On a number of boards the !RE signal is tied to ground so reception > is always enabled except if the UART allows disabling the receiver. > This can be taken advantage of to implement half-duplex mode - like > done on 8250_bcm2835aux. > > Another solution is to tie !RE to RTS always forcing half-duplex mode. > > And finally there is the option to control the RE signal separately, > like done here by introducing a new rs485-specifc gpio that can be > set depending on the RX_DURING_TX setting in the common em485 callbacks. > + if (port->rs485_re_gpio) Redundant. Same for all other cases. > + gpiod_set_value(port->rs485_re_gpio, 1); > + port->rs485_re_gpio = devm_gpiod_get(dev, "rs485-rx-enable", > + GPIOD_FLAGS_BIT_DIR_OUT); > + if (IS_ERR(port->rs485_re_gpio)) { > + ret = PTR_ERR(port->rs485_re_gpio); > + port->rs485_re_gpio = NULL; > + if (ret != -ENOENT) { > + if (ret != -EPROBE_DEFER) > + dev_err(dev, "Cannot get rs485-rx-enable-gpios\n"); > + return ret; > + } > + } NIH of gpiod_get_optional(). -- With Best Regards, Andy Shevchenko