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=-9.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,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 A27BBECDE46 for ; Thu, 25 Oct 2018 14:20:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 61E42208A3 for ; Thu, 25 Oct 2018 14:20:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="m62KAKL9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 61E42208A3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.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 S1731080AbeJYWxb (ORCPT ); Thu, 25 Oct 2018 18:53:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:36046 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731064AbeJYWx3 (ORCPT ); Thu, 25 Oct 2018 18:53:29 -0400 Received: from sasha-vm.mshome.net (unknown [167.98.65.38]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 787232146E; Thu, 25 Oct 2018 14:20:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1540477231; bh=KM1UJBXYeA0QVo4eoGyHMkI5gUhlNOVS3DwVonlzS6o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=m62KAKL9vNhhELw8CEWiE7zsR9GgCdmSZ9DvtNiEjGAvIQFftAPngT60ye1adpt9B wHDCMtYmu5rbNC1uLUxpIwjroehmkG59Rx6IfoVIbHEtFqtK6hsAuoclA6oJHC/faT BsUeW6I1on2M0ruc6a4uJAMoR+Hgmy+Ds+1BRdgE= From: Sasha Levin To: stable@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Stefan Agner , Bhuvanchandra DV , Greg Kroah-Hartman , Sasha Levin Subject: [PATCH AUTOSEL 3.18 64/98] tty: serial: fsl_lpuart: fix clearing of receive flag Date: Thu, 25 Oct 2018 10:18:19 -0400 Message-Id: <20181025141853.214051-64-sashal@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181025141853.214051-1-sashal@kernel.org> References: <20181025141853.214051-1-sashal@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Stefan Agner [ 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