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=unavailable 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 D12B8C04EBF for ; Mon, 23 Sep 2019 13:59:30 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A6E9520835 for ; Mon, 23 Sep 2019 13:59:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Y6lIN/g3" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A6E9520835 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=emlix.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:To :From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=ku9zQbqznHW0OjI6jw/rP129OD1Eg6IYyCtoDJWDHqg=; b=Y6lIN/g3PiOGLO Wqe9P8UqTY+v/0ICWDy92uZmAXVBeTZQX/LFVbysNRFmgc5MOhPKcKfSpcHCQWOXoCqjEen465QzH 7gvLiFIZ8lZTFcqfbfFSe/QXnVeBD/19KB72lmcySdjUdm8byGVOI7eCxo7dOiq0uO3AJWBbaX31Y hxoVlUu7v8qt7hvRtMX3YhD3uEKnKH7NhPU1fq80n7jwW5IBRMTCC7WoagXhgntgUMeZUaV0md93B DzGPbdvQnscBYKHAqsow5qpiyA4NYQmUVcpKd4EVj/716y4K/ZCF37s23L8SqVrqSfQGT2IN7gs+W UL0lPLe84HVdm8Y6vsuw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1iCOs9-0006dL-SL; Mon, 23 Sep 2019 13:59:26 +0000 Received: from mx1.emlix.com ([188.40.240.192]) by bombadil.infradead.org with esmtps (Exim 4.92.2 #3 (Red Hat Linux)) id 1iCOrU-0005wq-Ge for linux-arm-kernel@lists.infradead.org; Mon, 23 Sep 2019 13:58:46 +0000 Received: from mailer.emlix.com (unknown [81.20.119.6]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.emlix.com (Postfix) with ESMTPS id 476D85FBA6; Mon, 23 Sep 2019 15:58:43 +0200 (CEST) From: Philipp Puschmann To: linux-kernel@vger.kernel.org Subject: [PATCH v3] serial: imx: adapt rx buffer and dma periods Date: Mon, 23 Sep 2019 15:58:42 +0200 Message-Id: <20190923135842.956-1-philipp.puschmann@emlix.com> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190923_065844_797634_0F13BC80 X-CRM114-Status: GOOD ( 12.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: festevam@gmail.com, fugang.duan@nxp.com, linux-serial@vger.kernel.org, gregkh@linuxfoundation.org, s.hauer@pengutronix.de, u.kleine-koenig@pengutronix.de, linux-imx@nxp.com, kernel@pengutronix.de, jslaby@suse.com, Philipp Puschmann , yibin.gong@nxp.com, shawnguo@kernel.org, linux-arm-kernel@lists.infradead.org, l.stach@pengutronix.de Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Using only 4 DMA periods for UART RX is very few if we have a high frequency of small transfers - like in our case using Bluetooth with many small packets via UART - causing many dma transfers but in each only filling a fraction of a single buffer. Such a case may lead to the situation that DMA RX transfer is triggered but no free buffer is available. When this happens dma channel ist stopped - with the patch "dmaengine: imx-sdma: fix dma freezes" temporarily only - with the possible consequences that: with disabled hw flow control: If enough data is incoming on UART port the RX FIFO runs over and characters will be lost. What then happens depends on upper layer. with enabled hw flow control: If enough data is incoming on UART port the RX FIFO reaches a level where CTS is deasserted and remote device sending the data stops. If it fails to stop timely the i.MX' RX FIFO may run over and data get lost. Otherwise it's internal TX buffer may getting filled to a point where it runs over and data is again lost. It depends on the remote device how this case is handled and if it is recoverable. Obviously we want to avoid having no free buffers available. So we decrease the size of the buffers and increase their number and the total buffer size. Signed-off-by: Philipp Puschmann Reviewed-by: Lucas Stach --- Changelog v4: - fix total buffer size Changelog v3: - enhance description Changelog v2: - split this patch from series "Fix UART DMA freezes for iMX6" - add Reviewed-by tag drivers/tty/serial/imx.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 87c58f9f6390..51dc19833eab 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -1034,8 +1034,6 @@ static void imx_uart_timeout(struct timer_list *t) } } -#define RX_BUF_SIZE (PAGE_SIZE) - /* * There are two kinds of RX DMA interrupts(such as in the MX6Q): * [1] the RX DMA buffer is full. @@ -1118,7 +1116,8 @@ static void imx_uart_dma_rx_callback(void *data) } /* RX DMA buffer periods */ -#define RX_DMA_PERIODS 4 +#define RX_DMA_PERIODS 16 +#define RX_BUF_SIZE (RX_DMA_PERIODS * PAGE_SIZE / 4) static int imx_uart_start_rx_dma(struct imx_port *sport) { -- 2.23.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel