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 92C7CC3A5A6 for ; Thu, 19 Sep 2019 14:51:25 +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 670FF2067B for ; Thu, 19 Sep 2019 14:51:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="WyRy9Mot" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 670FF2067B 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=e66Ro2S6SQHoQo9zh71nrZQ+DwymlUzeiEsfg1Hxe/4=; b=WyRy9MotaytQ3l RFxzLzr3sFODPBEdyMjUBTLMsptiNQ4Sqqqv+z3VDUovQLp8lZRIvQIyydC+qTAxfNiqQ5REf09Cd aa/kkDg/hRS6Lc+3O27OEsRJvVABqHQgJ5q96Ycy0AmzsWMPaJLScF6OZ/k+ArLCnJKJw9XgL1c1y NWHEkviZdXNJmLkH/MC+Ps5QSLZaLExQxSDgtHR2xnJLomFa+zAgd4Pi2fTxu+8iQEllOSgISQw+/ BT5r8pW9v65p7JsKvGpTW7Gh5QKgO5OI+0/E+vllpqgjM2Km4ov8DfZrlln3sBO878DQhYxslfwYT D3HkZXmoaziSig4cGcjw==; 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 1iAxmG-000554-CE; Thu, 19 Sep 2019 14:51:24 +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 1iAxmC-00054P-7Z for linux-arm-kernel@lists.infradead.org; Thu, 19 Sep 2019 14:51:21 +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 213045FD85; Thu, 19 Sep 2019 16:51:18 +0200 (CEST) From: Philipp Puschmann To: linux-kernel@vger.kernel.org Subject: [PATCH v3] serial: imx: adapt rx buffer and dma periods Date: Thu, 19 Sep 2019 16:51:14 +0200 Message-Id: <20190919145114.13006-1-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-20190919_075120_421704_7896A4BC X-CRM114-Status: GOOD ( 12.39 ) 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 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 (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