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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8F65C433EF for ; Thu, 23 Jun 2022 17:51:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235315AbiFWRv4 (ORCPT ); Thu, 23 Jun 2022 13:51:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235191AbiFWRvW (ORCPT ); Thu, 23 Jun 2022 13:51:22 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C9F10563A1; Thu, 23 Jun 2022 10:12:24 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 88F9F61D02; Thu, 23 Jun 2022 17:12:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74C44C3411B; Thu, 23 Jun 2022 17:12:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1656004337; bh=qDzmuSiqbUB+FjyDOoGuytMegQAGK7PpdDB2C/Si6hM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cy5koJkjk+Nw7SjPnE3/4Hb8bWvhNZeBZk3lxslvA0VwhfBY+qjoI/V3JDGTZqhWz Z+fa+ikKL4Tq8uugioc82Y04hvqPa2QaUdblDC6U+nzeqm6MdwoRcaKBPqz8rG49Ag 3VJRZdhMdIeb/ehlGQBf2a5RT4N0KS9NLWCgMpnU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jan Kiszka , Su Bao Cheng , Lukas Wunner Subject: [PATCH 5.15 8/9] serial: core: Initialize rs485 RTS polarity already on probe Date: Thu, 23 Jun 2022 18:44:51 +0200 Message-Id: <20220623164322.534186490@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220623164322.288837280@linuxfoundation.org> References: <20220623164322.288837280@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lukas Wunner commit 2dd8a74fddd21b95dcc60a2d3c9eaec993419d69 upstream. RTS polarity of rs485-enabled ports is currently initialized on uart open via: tty_port_open() tty_port_block_til_ready() tty_port_raise_dtr_rts() # if (C_BAUD(tty)) uart_dtr_rts() uart_port_dtr_rts() There's at least three problems here: First, if no baud rate is set, RTS polarity is not initialized. That's the right thing to do for rs232, but not for rs485, which requires that RTS is deasserted unconditionally. Second, if the DeviceTree property "linux,rs485-enabled-at-boot-time" is present, RTS should be deasserted as early as possible, i.e. on probe. Otherwise it may remain asserted until first open. Third, even though RTS is deasserted on open and close, it may subsequently be asserted by uart_throttle(), uart_unthrottle() or uart_set_termios() because those functions aren't rs485-aware. (Only uart_tiocmset() is.) To address these issues, move RTS initialization from uart_port_dtr_rts() to uart_configure_port(). Prevent subsequent modification of RTS polarity by moving the existing rs485 check from uart_tiocmget() to uart_update_mctrl(). That way, RTS is initialized on probe and then remains unmodified unless the uart transmits data. If rs485 is enabled at runtime (instead of at boot) through a TIOCSRS485 ioctl(), RTS is initialized by the uart driver's ->rs485_config() callback and then likewise remains unmodified. The PL011 driver initializes RTS on uart open and prevents subsequent modification in its ->set_mctrl() callback. That code is obsoleted by the present commit, so drop it. Cc: Jan Kiszka Cc: Su Bao Cheng Signed-off-by: Lukas Wunner Link: https://lore.kernel.org/r/2d2acaf3a69e89b7bf687c912022b11fd29dfa1e.1642909284.git.lukas@wunner.de Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/amba-pl011.c | 15 +-------------- drivers/tty/serial/serial_core.c | 34 ++++++++++++---------------------- 2 files changed, 13 insertions(+), 36 deletions(-) --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -1620,13 +1620,6 @@ static void pl011_set_mctrl(struct uart_ container_of(port, struct uart_amba_port, port); unsigned int cr; - if (port->rs485.flags & SER_RS485_ENABLED) { - if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND) - mctrl &= ~TIOCM_RTS; - else - mctrl |= TIOCM_RTS; - } - cr = pl011_read(uap, REG_CR); #define TIOCMBIT(tiocmbit, uartbit) \ @@ -1850,14 +1843,8 @@ static int pl011_startup(struct uart_por cr = uap->old_cr & (UART011_CR_RTS | UART011_CR_DTR); cr |= UART01x_CR_UARTEN | UART011_CR_RXE; - if (port->rs485.flags & SER_RS485_ENABLED) { - if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND) - cr &= ~UART011_CR_RTS; - else - cr |= UART011_CR_RTS; - } else { + if (!(port->rs485.flags & SER_RS485_ENABLED)) cr |= UART011_CR_TXE; - } pl011_write(cr, uap, REG_CR); --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -144,6 +144,11 @@ uart_update_mctrl(struct uart_port *port unsigned long flags; unsigned int old; + if (port->rs485.flags & SER_RS485_ENABLED) { + set &= ~TIOCM_RTS; + clear &= ~TIOCM_RTS; + } + spin_lock_irqsave(&port->lock, flags); old = port->mctrl; port->mctrl = (old & ~clear) | set; @@ -157,23 +162,10 @@ uart_update_mctrl(struct uart_port *port static void uart_port_dtr_rts(struct uart_port *uport, int raise) { - int rs485_on = uport->rs485_config && - (uport->rs485.flags & SER_RS485_ENABLED); - int RTS_after_send = !!(uport->rs485.flags & SER_RS485_RTS_AFTER_SEND); - - if (raise) { - if (rs485_on && RTS_after_send) { - uart_set_mctrl(uport, TIOCM_DTR); - uart_clear_mctrl(uport, TIOCM_RTS); - } else { - uart_set_mctrl(uport, TIOCM_DTR | TIOCM_RTS); - } - } else { - unsigned int clear = TIOCM_DTR; - - clear |= (!rs485_on || RTS_after_send) ? TIOCM_RTS : 0; - uart_clear_mctrl(uport, clear); - } + if (raise) + uart_set_mctrl(uport, TIOCM_DTR | TIOCM_RTS); + else + uart_clear_mctrl(uport, TIOCM_DTR | TIOCM_RTS); } /* @@ -1089,11 +1081,6 @@ uart_tiocmset(struct tty_struct *tty, un goto out; if (!tty_io_error(tty)) { - if (uport->rs485.flags & SER_RS485_ENABLED) { - set &= ~TIOCM_RTS; - clear &= ~TIOCM_RTS; - } - uart_update_mctrl(uport, set, clear); ret = 0; } @@ -2408,6 +2395,9 @@ uart_configure_port(struct uart_driver * */ spin_lock_irqsave(&port->lock, flags); port->mctrl &= TIOCM_DTR; + if (port->rs485.flags & SER_RS485_ENABLED && + !(port->rs485.flags & SER_RS485_RTS_AFTER_SEND)) + port->mctrl |= TIOCM_RTS; port->ops->set_mctrl(port, port->mctrl); spin_unlock_irqrestore(&port->lock, flags);