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 B0E79C3A5A6 for ; Thu, 19 Sep 2019 10:47:32 +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 83773207FC for ; Thu, 19 Sep 2019 10:47:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="GwLUbmHf" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 83773207FC 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:References:In-Reply-To: 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: List-Owner; bh=WM8Kg23znsb43O6iUQdAIVGNH4trRvqNDM6bW++bREQ=; b=GwLUbmHfNuX6ep /QZDmzXqzxO+j2aPeDLBXftyYHkXjTCAOuiU4NyWUoP5+L5HN37UbY8SbiwDsBz8AI9xMO9A7jrdV Ye2UhcrsYOZk/grbtOCZMqgDK7poYfa4X5n3gk2fEWLXc7QX2EJRlKCQp9U4N4NQC7T4Sjd7F/GP9 ZgD1qvTk1HN3X2jcg8RfhmmR8JkqJa8VcdkM3fnsGAGFerC4+U+dU5hvR5KFLi/IXVsfzZf5xsdBE 72jQVQowYQJheKoHNT65FSRcR1vKP1YAvsfpTrYoRGxFO1W3NlRC1h0jmsmsDZciNHDyLPm0J5uxw P60meBhm2xNqYWXXmdGw==; 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 1iAtyA-0004SG-LA; Thu, 19 Sep 2019 10:47:26 +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 1iAtwK-0003XW-Dr for linux-arm-kernel@lists.infradead.org; Thu, 19 Sep 2019 10:45:35 +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 3A861603E1; Thu, 19 Sep 2019 12:45:31 +0200 (CEST) From: Philipp Puschmann To: linux-kernel@vger.kernel.org Subject: [PATCH v3 2/3] dmaengine: imx-sdma: fix dma freezes Date: Thu, 19 Sep 2019 12:45:25 +0200 Message-Id: <20190919104526.29851-3-philipp.puschmann@emlix.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190919104526.29851-1-philipp.puschmann@emlix.com> References: <20190919102319.23368-1-philipp.puschmann@emlix.com> <20190919104526.29851-1-philipp.puschmann@emlix.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190919_034532_620055_2D452737 X-CRM114-Status: GOOD ( 15.95 ) 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: fugang.duan@nxp.com, Philipp Puschmann , festevam@gmail.com, s.hauer@pengutronix.de, vkoul@kernel.org, linux-imx@nxp.com, kernel@pengutronix.de, dan.j.williams@intel.com, yibin.gong@nxp.com, shawnguo@kernel.org, dmaengine@vger.kernel.or, 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 For some years and since many kernel versions there are reports that the RX UART SDMA channel stops working at some point. The workaround was to disable DMA for RX. This commit tries to fix the problem itself. Due to its license i wasn't able to debug the sdma script itself but it somehow leads to blocking the scheduling of the channel script when a running sdma script does not find any free descriptor in the ring to put its data into. If we detect such a potential case we manually restart the channel. As sdmac->desc is constant we can move desc out of the loop. Fixes: broken UART RX DMA. broken since start Signed-off-by: Philipp Puschmann Reviewed-by: Lucas Stach --- Changelog v3: - use correct dma_wmb() instead of dma_wb() - add fixes tag Changelog v2: - clarify comment and commit description drivers/dma/imx-sdma.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c index e029a2443cfc..a32b5962630e 100644 --- a/drivers/dma/imx-sdma.c +++ b/drivers/dma/imx-sdma.c @@ -775,21 +775,23 @@ static void sdma_start_desc(struct sdma_channel *sdmac) static void sdma_update_channel_loop(struct sdma_channel *sdmac) { struct sdma_buffer_descriptor *bd; - int error = 0; - enum dma_status old_status = sdmac->status; + struct sdma_desc *desc = sdmac->desc; + int error = 0, cnt = 0; + enum dma_status old_status = sdmac->status; /* * loop mode. Iterate over descriptors, re-setup them and * call callback function. */ - while (sdmac->desc) { - struct sdma_desc *desc = sdmac->desc; + while (desc) { bd = &desc->bd[desc->buf_tail]; if (bd->mode.status & BD_DONE) break; + cnt++; + if (bd->mode.status & BD_RROR) { bd->mode.status &= ~BD_RROR; sdmac->status = DMA_ERROR; @@ -822,6 +824,17 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac) if (error) sdmac->status = old_status; } + + /* In some situations it may happen that the sdma does not found any + * usable descriptor in the ring to put data into. The channel is + * stopped then. While there is no specific error condition we can + * check for, a necessary condition is that all available buffers for + * the current channel have been written to by the sdma script. In + * this case and after we have made the buffers available again, + * we restart the channel. + */ + if (cnt >= desc->num_bd) + sdma_enable_channel(sdmac->sdma, sdmac->channel); } static void mxc_sdma_handle_channel_normal(struct sdma_channel *data) -- 2.23.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel