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=-10.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 095DEC43441 for ; Thu, 8 Nov 2018 22:41:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C1D0920844 for ; Thu, 8 Nov 2018 22:41:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="wQ6QE70M" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C1D0920844 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728977AbeKIHdj (ORCPT ); Fri, 9 Nov 2018 02:33:39 -0500 Received: from mail.kernel.org ([198.145.29.99]:49456 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728951AbeKIHdi (ORCPT ); Fri, 9 Nov 2018 02:33:38 -0500 Received: from localhost (unknown [208.72.13.198]) (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 C31D220892; Thu, 8 Nov 2018 21:56:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1541714170; bh=YLmCx82ocb9RuUFgAsuHuhj8YE/KYq8DRgy4fJa4RQU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wQ6QE70MomBCDQbB5DZUNxYz9eEkBc19K+Iuya6d3cLpjjB9mu0F1J2Id8LhUoI9E po4Sj7ElgCh2XNnUjKZ8yI2WEHy4c27A3Ti0HiNo1j3npx50CH9SXbsuxz6+kBeFHJ IP8RZBi2VImQV6Lk9v3ziUO2Ps8JcRMZceZWOp8U= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Stefan Agner , Bhuvanchandra DV , Sasha Levin Subject: [PATCH 3.18 093/144] tty: serial: fsl_lpuart: fix clearing of receive flag Date: Thu, 8 Nov 2018 13:51:04 -0800 Message-Id: <20181108215103.075842925@linuxfoundation.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20181108215054.826084593@linuxfoundation.org> References: <20181108215054.826084593@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review 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 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit d68827c62a105eec547945daedf4d1d3e283717d ] Commit 8e4934c6d6c6 ("tty: serial: fsl_lpuart: clear receive flag on FIFO flush") implemented clearing of the receive flag by reading the status register only. It turned out that even though we flush the FIFO afterwards, a explicit read of the data register is still required. This leads to a FIFO underrun. To avoid this, follow the advice in the overrun "Operation section": Unconditionally clear RXUF after using RXFLUSH. Signed-off-by: Stefan Agner Signed-off-by: Bhuvanchandra DV Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/fsl_lpuart.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index af3047d8322a..92b7a5bf7c4d 100644 --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -910,13 +910,16 @@ static void lpuart_setup_watermark(struct lpuart_port *sport) writeb(val | UARTPFIFO_TXFE | UARTPFIFO_RXFE, sport->port.membase + UARTPFIFO); - /* explicitly clear RDRF */ - readb(sport->port.membase + UARTSR1); - /* flush Tx and Rx FIFO */ writeb(UARTCFIFO_TXFLUSH | UARTCFIFO_RXFLUSH, sport->port.membase + UARTCFIFO); + /* explicitly clear RDRF */ + if (readb(sport->port.membase + UARTSR1) & UARTSR1_RDRF) { + readb(sport->port.membase + UARTDR); + writeb(UARTSFIFO_RXUF, sport->port.membase + UARTSFIFO); + } + writeb(0, sport->port.membase + UARTTWFIFO); writeb(1, sport->port.membase + UARTRWFIFO); -- 2.17.1