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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT 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 E05AAC43381 for ; Tue, 19 Mar 2019 13:20:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B9EC020857 for ; Tue, 19 Mar 2019 13:20:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727430AbfCSNUp (ORCPT ); Tue, 19 Mar 2019 09:20:45 -0400 Received: from esa2.microchip.iphmx.com ([68.232.149.84]:32641 "EHLO esa2.microchip.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726007AbfCSNUn (ORCPT ); Tue, 19 Mar 2019 09:20:43 -0400 X-IronPort-AV: E=Sophos;i="5.58,498,1544511600"; d="scan'208";a="28347289" Received: from smtpout.microchip.com (HELO email.microchip.com) ([198.175.253.82]) by esa2.microchip.iphmx.com with ESMTP/TLS/DHE-RSA-AES256-SHA; 19 Mar 2019 06:20:42 -0700 Received: from rob-ult-m50855.microchip.com (10.10.76.4) by chn-sv-exch03.mchp-main.com (10.10.76.49) with Microsoft SMTP Server id 14.3.352.0; Tue, 19 Mar 2019 06:20:42 -0700 From: Razvan Stefanescu To: Richard Genoud , Greg Kroah-Hartman , Jiri Slaby CC: Gil Weber , Nicolas Ferre , Alexandre Belloni , Ludovic Desroches , , , Subject: [PATCH v2 2/2] tty/serial: atmel: RS485 HD w/DMA: enable RX after TX is stopped Date: Tue, 19 Mar 2019 15:20:35 +0200 Message-ID: <20190319132035.18481-3-razvan.stefanescu@microchip.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190319132035.18481-1-razvan.stefanescu@microchip.com> References: <20190319132035.18481-1-razvan.stefanescu@microchip.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In half-duplex operation, RX should be started after TX completes. If DMA is used, there is a case when the DMA transfer completes but the TX FIFO is not emptied, so the RX cannot be restarted just yet. Use a boolean variable to store this state and rearm TX interrupt mask to be signaled again that the transfer finished. In interrupt transmit handler this variable is used to start RX. A warning message is generated if RX is activated before TX fifo is cleared. Fixes: b389f173aaa1 ("tty/serial: atmel: RS485 half duplex w/DMA: enable RX after TX is done") Signed-off-by: Razvan Stefanescu --- Changelog: v2: - start RX and display warning in case of error - add fix info drivers/tty/serial/atmel_serial.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c index b4b89a16a41b..5b2f859c327c 100644 --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -166,6 +166,8 @@ struct atmel_uart_port { unsigned int pending_status; spinlock_t lock_suspended; + bool hd_start_rx; /* can start RX during half-duplex operation */ + /* ISO7816 */ unsigned int fidi_min; unsigned int fidi_max; @@ -933,8 +935,13 @@ static void atmel_complete_tx_dma(void *arg) if (!uart_circ_empty(xmit)) atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx); else if (atmel_uart_is_half_duplex(port)) { - /* DMA done, stop TX, start RX for RS485 */ - atmel_start_rx(port); + /* + * DMA done, re-enable TXEMPTY and signal that we can stop + * TX and start RX for RS485 + */ + atmel_port->hd_start_rx = true; + atmel_uart_writel(port, ATMEL_US_IER, + atmel_port->tx_done_mask); } spin_unlock_irqrestore(&port->lock, flags); @@ -1378,9 +1385,20 @@ atmel_handle_transmit(struct uart_port *port, unsigned int pending) struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); if (pending & atmel_port->tx_done_mask) { - /* Either PDC or interrupt transmission */ atmel_uart_writel(port, ATMEL_US_IDR, atmel_port->tx_done_mask); + + /* Start RX if flag was set and FIFO is empty */ + if (atmel_port->hd_start_rx) { + if (!(atmel_uart_readl(port, ATMEL_US_CSR) + & ATMEL_US_TXEMPTY)) + dev_warn(port->dev, "Should start RX, but TX fifo is not empty\n"); + + atmel_port->hd_start_rx = false; + atmel_start_rx(port); + return; + } + atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx); } } -- 2.19.1