From nobody Mon Feb 9 06:04:57 2026 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 7CB01EB64D7 for ; Fri, 16 Jun 2023 10:57:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345510AbjFPK5C (ORCPT ); Fri, 16 Jun 2023 06:57:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51064 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345469AbjFPK4n (ORCPT ); Fri, 16 Jun 2023 06:56:43 -0400 Received: from mail-ed1-x561.google.com (mail-ed1-x561.google.com [IPv6:2a00:1450:4864:20::561]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7130A83C9 for ; Fri, 16 Jun 2023 03:48:41 -0700 (PDT) Received: by mail-ed1-x561.google.com with SMTP id 4fb4d7f45d1cf-514ab6cb529so3532584a12.1 for ; Fri, 16 Jun 2023 03:48:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=flowbird.group; s=google; t=1686912520; x=1689504520; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=C6sTC5pGl6XNZzwmeNOE7S97A8pGrSyNQTyHwRNfok4=; b=H7e4PJE/COEkCn7uTaLOPIHdqIsgSCthKaI8FdezrQFFKELM6pfMfr8Z1F7eOuAaq2 j+CERzJ+3Dfjmjk8LJXwQWZxJZdhNekRWlMPyhuXq6SxKVj9kxnwtQAACMxogox2fwtl +zOwbQ69G9kgDuAmbLT799Zd2rEJkbUzA/OH47llA4lm2qMkO3OeBFVyQ+fVMnmdg0Q5 1OFRxpPxdq0usTLnqSpFpmCaowj8HSi7qsWRcmpcP9RE3q8aCedi1ERnzBEgpFiNXFVG 8dSCBxqjzWbyGY2pWEbkqmlUNgqaBDoU+4nb0IKgIgIHRUoHK+66fS6ByPeTSv98yN0G YXwA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1686912520; x=1689504520; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=C6sTC5pGl6XNZzwmeNOE7S97A8pGrSyNQTyHwRNfok4=; b=DycRg4wGJaDSFucAOm57KDG5UimTEoIqiADJvro6OIoqkyau/Cfx0EqNFXwKZu1XNP le89VDmLFfiPs0910NdvQbWopyzCUiHUrAGTnpiOMjr6cseGwCIxENOUnr9i+whVQWko A1JkJ2B/v5jPilykAgKTW8ADJVwxA9o5o5VjTjFQq/WEhKTwe+SxGR3RtxfgrQFhh2ii UFipgIfqLQM8mSTccczNqkYJ/IJ9/rubYZjFjA/eg4Jai2E7XW9QkaPe0zbTKzolMuJd su9t39hKDYVjZrWvAPQzpKZFByedfvDhxIwtVxYLz6YpzH07mNK8fmu9FZyawofRNVTk vohA== X-Gm-Message-State: AC+VfDyWH5aZamDUJVzJKGrjmkz0iu+M0BjCnbOI1oHMBWrBnAwnFeVj IxKDTzB1HeP+4cUuJwacPWg3+HbIXzTSmAacTIEY7IMvxn1Q X-Google-Smtp-Source: ACHHUZ60gXe4Q/+sJTSC6YdsfA/nL9NJtZAhb8u35HcJ9uttZCHSH+pIn9G6B+2RlR6ILarkqm4H1xKm/r3r X-Received: by 2002:a17:907:d11:b0:96f:9cea:a34d with SMTP id gn17-20020a1709070d1100b0096f9ceaa34dmr7697675ejc.21.1686912519734; Fri, 16 Jun 2023 03:48:39 -0700 (PDT) Received: from mta1.parkeon.com ([185.149.63.251]) by smtp-relay.gmail.com with ESMTPS id cs20-20020a170906dc9400b0098634569b96sm1092294ejc.288.2023.06.16.03.48.39 (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 16 Jun 2023 03:48:39 -0700 (PDT) X-Relaying-Domain: flowbird.group Received: from [172.16.12.142] (port=33732 helo=FR-BES-DKT15120.home) by mta1.parkeon.com with esmtp (Exim 4.71) (envelope-from ) id 1qA72r-0000gy-MC; Fri, 16 Jun 2023 12:51:09 +0200 From: Martin Fuzzey To: linux-serial@vger.kernel.org Cc: Greg Kroah-Hartman , Shawn Guo , Fabio Estevam , Marek Vasut , linux-kernel@vger.kernel.org Subject: [PATCH] tty: serial: imx: fix rs485 rx after tx Date: Fri, 16 Jun 2023 12:47:23 +0200 Message-Id: <20230616104838.2729694-1-martin.fuzzey@flowbird.group> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Since commit 79d0224f6bf2 ("tty: serial: imx: Handle RS485 DE signal active high") RS485 reception no longer works after a transmission. The following scenario shows the problem: 1) Open a port in RS485 mode 2) Receive data from remote (OK) 3) Transmit data to remote (OK) 4) Receive data from remote (Nothing received) In RS485 mode, imx_uart_start_tx() calls imx_uart_stop_rx() and, when the transmission is complete, imx_uart_stop_tx() calls imx_uart_start_rx(). Since the above commit imx_uart_stop_rx() now sets the loopback bit but imx_uart_start_rx() does not clear it causing the hardware to remain in loopback mode and not receive external data. Fix this by moving the existing loopback disable code to a helper function and calling it from imx_uart_start_rx() too. Fixes: 79d0224f6bf2 ("tty: serial: imx: Handle RS485 DE signal active high") Cc: stable@vger.kernel.org Signed-off-by: Martin Fuzzey Reviewed-by: Ilpo J=C3=A4rvinen --- drivers/tty/serial/imx.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index c5e17569c3ad..3fe8ff241522 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -369,6 +369,16 @@ static void imx_uart_soft_reset(struct imx_port *sport) sport->idle_counter =3D 0; } =20 +static void imx_uart_disable_loopback_rs485(struct imx_port *sport) +{ + unsigned int uts; + + /* See SER_RS485_ENABLED/UTS_LOOP comment in imx_uart_probe() */ + uts =3D imx_uart_readl(sport, imx_uart_uts_reg(sport)); + uts &=3D ~UTS_LOOP; + imx_uart_writel(sport, uts, imx_uart_uts_reg(sport)); +} + /* called with port.lock taken and irqs off */ static void imx_uart_start_rx(struct uart_port *port) { @@ -390,6 +400,7 @@ static void imx_uart_start_rx(struct uart_port *port) /* Write UCR2 first as it includes RXEN */ imx_uart_writel(sport, ucr2, UCR2); imx_uart_writel(sport, ucr1, UCR1); + imx_uart_disable_loopback_rs485(sport); } =20 /* called with port.lock taken and irqs off */ @@ -1422,7 +1433,7 @@ static int imx_uart_startup(struct uart_port *port) int retval; unsigned long flags; int dma_is_inited =3D 0; - u32 ucr1, ucr2, ucr3, ucr4, uts; + u32 ucr1, ucr2, ucr3, ucr4; =20 retval =3D clk_prepare_enable(sport->clk_per); if (retval) @@ -1521,10 +1532,7 @@ static int imx_uart_startup(struct uart_port *port) imx_uart_writel(sport, ucr2, UCR2); } =20 - /* See SER_RS485_ENABLED/UTS_LOOP comment in imx_uart_probe() */ - uts =3D imx_uart_readl(sport, imx_uart_uts_reg(sport)); - uts &=3D ~UTS_LOOP; - imx_uart_writel(sport, uts, imx_uart_uts_reg(sport)); + imx_uart_disable_loopback_rs485(sport); =20 spin_unlock_irqrestore(&sport->port.lock, flags); =20 --=20 2.25.1