From patchwork Tue May 5 14:42:04 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lukas Wunner X-Patchwork-Id: 214029 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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED 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 D60F6C47247 for ; Tue, 5 May 2020 14:49:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B8373206B9 for ; Tue, 5 May 2020 14:49:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729194AbgEEOts (ORCPT ); Tue, 5 May 2020 10:49:48 -0400 Received: from mailout3.hostsharing.net ([176.9.242.54]:45527 "EHLO mailout3.hostsharing.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729060AbgEEOts (ORCPT ); Tue, 5 May 2020 10:49:48 -0400 Received: from h08.hostsharing.net (h08.hostsharing.net [83.223.95.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "*.hostsharing.net", Issuer "COMODO RSA Domain Validation Secure Server CA" (not verified)) by mailout3.hostsharing.net (Postfix) with ESMTPS id A383B100A5F0F; Tue, 5 May 2020 16:49:45 +0200 (CEST) Received: from localhost (unknown [87.130.102.138]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by h08.hostsharing.net (Postfix) with ESMTPSA id 3114D610EE1A; Tue, 5 May 2020 16:49:45 +0200 (CEST) X-Mailbox-Line: From a91b9392e8e7914cae16f59beb1ffe6b335f81c9 Mon Sep 17 00:00:00 2001 Message-Id: In-Reply-To: References: From: Lukas Wunner Date: Tue, 5 May 2020 16:42:04 +0200 Subject: [PATCH 4/4] serial: 8250: Support rs485 bus termination GPIO To: Greg Kroah-Hartman , Jiri Slaby , Rob Herring Cc: "Matwey V. Kornilov" , Giulio Benetti , Heiko Stuebner , Andy Shevchenko , Christoph Muellner , Jan Kiszka , devicetree@vger.kernel.org, linux-serial@vger.kernel.org Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Commit e8759ad17d41 ("serial: uapi: Add support for bus termination") introduced the ability to enable rs485 bus termination from user space. So far the feature is only used by a single driver, 8250_exar.c, using a hardcoded GPIO pin specific to Siemens IOT2040 products. Provide for a more generic solution by allowing specification of an rs485 bus termination GPIO pin in the device tree: Amend the serial core to retrieve the GPIO from the device tree (or ACPI table) and amend the default ->rs485_config() callback for 8250 drivers to change the GPIO on request from user space. Signed-off-by: Lukas Wunner --- drivers/tty/serial/8250/8250_port.c | 4 ++++ drivers/tty/serial/serial_core.c | 24 ++++++++++++++++++++++++ include/linux/serial_core.h | 2 ++ 3 files changed, 30 insertions(+) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index f77bf820b7a3..b5b630d02110 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -681,6 +681,10 @@ int serial8250_em485_config(struct uart_port *port, struct serial_rs485 *rs485) memset(rs485->padding, 0, sizeof(rs485->padding)); port->rs485 = *rs485; + if (port->rs485_term_gpio) + gpiod_set_value(port->rs485_term_gpio, + rs485->flags & SER_RS485_TERMINATE_BUS); + /* * Both serial8250_em485_init() and serial8250_em485_destroy() * are idempotent. diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 43b6682877d5..7c929aad066e 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -3317,6 +3317,7 @@ int uart_get_rs485_mode(struct uart_port *port) * to get to a defined state with the following properties: */ rs485conf->flags &= ~(SER_RS485_RX_DURING_TX | SER_RS485_ENABLED | + SER_RS485_TERMINATE_BUS | SER_RS485_RTS_AFTER_SEND); rs485conf->flags |= SER_RS485_RTS_ON_SEND; @@ -3331,6 +3332,29 @@ int uart_get_rs485_mode(struct uart_port *port) rs485conf->flags |= SER_RS485_RTS_AFTER_SEND; } + if (port->rs485_term_gpio) + devm_gpiod_put(dev, port->rs485_term_gpio); + + port->rs485_term_gpio = devm_gpiod_get_optional(dev, "rs485-term", + GPIOD_FLAGS_BIT_DIR_SET | GPIOD_FLAGS_BIT_DIR_OUT); + if (IS_ERR(port->rs485_term_gpio)) { + ret = PTR_ERR(port->rs485_term_gpio); + port->rs485_term_gpio = NULL; + if (ret != -EPROBE_DEFER) + dev_err(dev, "Cannot get rs485-term-gpios\n"); + return ret; + } + + if (port->rs485_term_gpio) { + ret = gpiod_get_value(port->rs485_term_gpio); + if (ret < 0) { + dev_err(dev, "Cannot get rs485-term-gpios value\n"); + return ret; + } + if (ret) + rs485conf->flags |= SER_RS485_TERMINATE_BUS; + } + return 0; } EXPORT_SYMBOL_GPL(uart_get_rs485_mode); diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index b649a2b894e7..9fd550e7946a 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -10,6 +10,7 @@ #include #include #include +#include #include #include #include @@ -251,6 +252,7 @@ struct uart_port { struct attribute_group *attr_group; /* port specific attributes */ const struct attribute_group **tty_groups; /* all attributes (serial core use only) */ struct serial_rs485 rs485; + struct gpio_desc *rs485_term_gpio; /* enable RS485 bus termination */ struct serial_iso7816 iso7816; void *private_data; /* generic platform data pointer */ };