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 DD676C433E0 for ; Mon, 18 May 2020 15:12:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A764E207D4 for ; Mon, 18 May 2020 15:12:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727020AbgERPMm (ORCPT ); Mon, 18 May 2020 11:12:42 -0400 Received: from mga07.intel.com ([134.134.136.100]:52402 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726998AbgERPMm (ORCPT ); Mon, 18 May 2020 11:12:42 -0400 IronPort-SDR: WmzkenqQiI/9y/7OhkbZm0Th+NcifX5ickffFZT1HqAoaSvaF7JjOwIu/tbL2SfFowvj+qzPhm PcuOh3JJQpAw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 May 2020 08:12:41 -0700 IronPort-SDR: lGoNwaSmCWCNYhxVwEIIKD1mnxX+M3JBB4K5asCGRZD4pIfOnOhf7oJqbdp0HpEXYaNBdqz0ap +8GLK/AvKu8Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,407,1583222400"; d="scan'208";a="439250139" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by orsmga005.jf.intel.com with ESMTP; 18 May 2020 08:12:39 -0700 Received: from andy by smile with local (Exim 4.93) (envelope-from ) id 1jahRZ-007S1V-Q9; Mon, 18 May 2020 18:12:41 +0300 Date: Mon, 18 May 2020 18:12:41 +0300 From: Andy Shevchenko To: Heiko Stuebner Cc: gregkh@linuxfoundation.org, jslaby@suse.com, matwey.kornilov@gmail.com, giulio.benetti@micronovasrl.com, lukas@wunner.de, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, christoph.muellner@theobroma-systems.com, Heiko Stuebner Subject: Re: [PATCH v3 3/5] serial: 8250: Support separate rs485 rx-enable GPIO Message-ID: <20200518151241.GG1634618@smile.fi.intel.com> References: <20200517215610.2131618-1-heiko@sntech.de> <20200517215610.2131618-4-heiko@sntech.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200517215610.2131618-4-heiko@sntech.de> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Sun, May 17, 2020 at 11:56:08PM +0200, 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-specific gpio that can be > set depending on the RX_DURING_TX setting in the common em485 callbacks. ... > + port->rs485_re_gpio = devm_gpiod_get_optional(dev, "rs485-rx-enable", > + GPIOD_OUT_HIGH); While reviewing some other patch I realized that people are missing the point of these GPIO flags when pin is declared to be output. HIGH here means "asserted" (consider active-high vs. active-low in general). Is that the intention here? Lukas, same question to your patch. -- With Best Regards, Andy Shevchenko