From patchwork Wed May 4 16:44:33 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "gregkh@linuxfoundation.org" X-Patchwork-Id: 569700 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 9E5E6C4332F for ; Wed, 4 May 2022 17:09:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355486AbiEDRNB (ORCPT ); Wed, 4 May 2022 13:13:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35802 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356821AbiEDRJp (ORCPT ); Wed, 4 May 2022 13:09:45 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D9783222A9; Wed, 4 May 2022 09:55:50 -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 ams.source.kernel.org (Postfix) with ESMTPS id 98CF7B82795; Wed, 4 May 2022 16:55:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 36A4BC385A4; Wed, 4 May 2022 16:55:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1651683348; bh=G71WT7nFX4UN9eB8Tn1SQhYCaU4g34pC/vPb7hR0lQI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UQ6QW0aXF5QZWfbMg8EaqbcJsUyXVmkndiycEuPubu5cHld0/x1lIvg74XPaNvtZ6 U6lGoLiTWGrCcZcuEpVPW7gF/1qLpKL1p1SAi+r642vTN6vCCf/ELmYu/5K1eWgPj3 o2nZWinhkbO5Zm1NLXWCTtmFGC45IieQUZdqCrNA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lino Sanfilippo Subject: [PATCH 5.17 035/225] serial: amba-pl011: do not time out prematurely when draining tx fifo Date: Wed, 4 May 2022 18:44:33 +0200 Message-Id: <20220504153113.350828662@linuxfoundation.org> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220504153110.096069935@linuxfoundation.org> References: <20220504153110.096069935@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Lino Sanfilippo commit 0e4deb56b0c625efdb70c94f150429e2f2a16fa1 upstream. The current timeout for draining the tx fifo in RS485 mode is calculated by multiplying the time it takes to transmit one character (with the given baud rate) with the maximal number of characters in the tx queue. This timeout is too short for two reasons: First when calculating the time to transmit one character integer division is used which may round down the result in case of a remainder of the division. Fix this by rounding up the division result. Second the hardware may need additional time (e.g for first putting the characters from the fifo into the shift register) before the characters are actually put onto the wire. To be on the safe side double the current maximum number of iterations that are used to wait for the queue draining. Fixes: 8d479237727c ("serial: amba-pl011: add RS485 support") Cc: stable@vger.kernel.org Signed-off-by: Lino Sanfilippo Link: https://lore.kernel.org/r/20220408233503.7251-1-LinoSanfilippo@gmx.de Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/amba-pl011.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -1255,13 +1255,18 @@ static inline bool pl011_dma_rx_running( static void pl011_rs485_tx_stop(struct uart_amba_port *uap) { + /* + * To be on the safe side only time out after twice as many iterations + * as fifo size. + */ + const int MAX_TX_DRAIN_ITERS = uap->port.fifosize * 2; struct uart_port *port = &uap->port; int i = 0; u32 cr; /* Wait until hardware tx queue is empty */ while (!pl011_tx_empty(port)) { - if (i == port->fifosize) { + if (i > MAX_TX_DRAIN_ITERS) { dev_warn(port->dev, "timeout while draining hardware tx queue\n"); break; @@ -2052,7 +2057,7 @@ pl011_set_termios(struct uart_port *port * with the given baud rate. We use this as the poll interval when we * wait for the tx queue to empty. */ - uap->rs485_tx_drain_interval = (bits * 1000 * 1000) / baud; + uap->rs485_tx_drain_interval = DIV_ROUND_UP(bits * 1000 * 1000, baud); pl011_setup_status_masks(port, termios);