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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,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 DAB29C76186 for ; Mon, 29 Jul 2019 19:37:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AB06B217D7 for ; Mon, 29 Jul 2019 19:37:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564429069; bh=bDfhRMuXP5B3GwHpV1Bk3DWSkybPAdwcpwijME229TQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=vruNy3GlAKDGYKbMTaFePBIRaT7n2OGbPRnOKFBR9mJ+4n48bzhTTGx0YYTGotu6w MBydoqtdIYEOjRY9DtEOHaZrUqfdzo36N1pHTPRRsPwdNthzVe6ygRT6T1hwovmkFU FMEj0L0mMdxlUwQFsXY1zxl4mnCqxI6u0ZpgS/Ts= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388783AbfG2Ths (ORCPT ); Mon, 29 Jul 2019 15:37:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:52638 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388750AbfG2Thq (ORCPT ); Mon, 29 Jul 2019 15:37:46 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 2615020C01; Mon, 29 Jul 2019 19:37:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564429065; bh=bDfhRMuXP5B3GwHpV1Bk3DWSkybPAdwcpwijME229TQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EN1wyJCbiBJF0S9Noh0wOBDi+6nTgxYZ4yrF6dyKgzwZWSRgDIX01HDqIXmu91CIN cXnIfebgNUE+bg1ow+q73VOKdD2DLsr4+4R6eWPDXcuNXc8BNDwQZLnVASMuOezP0z Z8VDc7+5F5DV9rM5mecGeFm5NKmSVy/49eong5xQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kimmo Rautkoski , Sasha Levin Subject: [PATCH 4.14 235/293] serial: 8250: Fix TX interrupt handling condition Date: Mon, 29 Jul 2019 21:22:06 +0200 Message-Id: <20190729190842.470737156@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190729190820.321094988@linuxfoundation.org> References: <20190729190820.321094988@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 [ Upstream commit db1b5bc047b3cadaedab3826bba82c3d9e023c4b ] Interrupt handler checked THRE bit (transmitter holding register empty) in LSR to detect if TX fifo is empty. In case when there is only receive interrupts the TX handling got called because THRE bit in LSR is set when there is no transmission (FIFO empty). TX handling caused TX stop, which in RS-485 half-duplex mode actually resets receiver FIFO. This is not desired during reception because of possible data loss. The fix is to check if THRI is set in IER in addition of the TX fifo status. THRI in IER is set when TX is started and cleared when TX is stopped. This ensures that TX handling is only called when there is really transmission on going and an interrupt for THRE and not when there are only RX interrupts. Signed-off-by: Kimmo Rautkoski Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/8250/8250_port.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index ab0796d14ac1..a73d2bc4b685 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1878,7 +1878,8 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir) status = serial8250_rx_chars(up, status); } serial8250_modem_status(up); - if ((!up->dma || up->dma->tx_err) && (status & UART_LSR_THRE)) + if ((!up->dma || up->dma->tx_err) && (status & UART_LSR_THRE) && + (up->ier & UART_IER_THRI)) serial8250_tx_chars(up); spin_unlock_irqrestore(&port->lock, flags); -- 2.20.1