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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 BDFE1C10F11 for ; Wed, 24 Apr 2019 17:17:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8D47321905 for ; Wed, 24 Apr 2019 17:17:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556126274; bh=QVyhPioUa5lmNvEIf7vChFK+1M3i3R5wyT007+FyYeY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=1AbAD2Kf12g2zH4Z+VrPm434pHPzrT9wOGLaaUSXjkVccair58J44WDg+LMtIyIkQ gVayH3o/VMkDMK0vhmSo7+D31NfGWfjLHUt+rOEoYdVoCMJ/IpJTb9krccmnWM+Zyo jyCwA9P0cMa30YSX2r1ffuTgTtKOcac3BbCpVIHY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388738AbfDXRRx (ORCPT ); Wed, 24 Apr 2019 13:17:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:42812 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388721AbfDXRRu (ORCPT ); Wed, 24 Apr 2019 13:17:50 -0400 Received: from localhost (62-193-50-229.as16211.net [62.193.50.229]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 506C22054F; Wed, 24 Apr 2019 17:17:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556126269; bh=QVyhPioUa5lmNvEIf7vChFK+1M3i3R5wyT007+FyYeY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=J/KTIgek6DRR6w3+Sv1lyU8Yy94NQCyMXqrfCE85X4SB5TTQECuGDOsu6dLx/jVdK yOy9WzUGE9lEFR9u0eh8/N5Wp3gvv2ZNJuWNJw2pgtinQXFclF7dGLCAXHeOUjsV8t NMkSk36z5PvygqrF7RQXG5x8LCno+T2eIW36JqJc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Razvan Stefanescu , Richard Genoud Subject: [PATCH 4.4 009/168] tty/serial: atmel: RS485 HD w/DMA: enable RX after TX is stopped Date: Wed, 24 Apr 2019 19:07:33 +0200 Message-Id: <20190424170924.038041486@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190424170923.452349382@linuxfoundation.org> References: <20190424170923.452349382@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Razvan Stefanescu commit 69646d7a3689fbe1a65ae90397d22ac3f1b8d40f upstream. 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 Acked-by: Richard Genoud Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/atmel_serial.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -169,6 +169,8 @@ struct atmel_uart_port { unsigned int pending_status; spinlock_t lock_suspended; + bool hd_start_rx; /* can start RX during half-duplex operation */ + int (*prepare_rx)(struct uart_port *port); int (*prepare_tx)(struct uart_port *port); void (*schedule_rx)(struct uart_port *port); @@ -816,8 +818,13 @@ static void atmel_complete_tx_dma(void * if (!uart_circ_empty(xmit)) tasklet_schedule(&atmel_port->tasklet); 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); @@ -1257,9 +1264,20 @@ atmel_handle_transmit(struct uart_port * 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; + } + tasklet_schedule(&atmel_port->tasklet); } }