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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=no 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 F05AAC3A5A6 for ; Thu, 19 Sep 2019 14:29:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AFF7221E6F for ; Thu, 19 Sep 2019 14:29:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389883AbfISO3r (ORCPT ); Thu, 19 Sep 2019 10:29:47 -0400 Received: from mx1.emlix.com ([188.40.240.192]:58576 "EHLO mx1.emlix.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730815AbfISO3r (ORCPT ); Thu, 19 Sep 2019 10:29:47 -0400 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 6289F5FD85; Thu, 19 Sep 2019 16:29:45 +0200 (CEST) From: Philipp Puschmann To: linux-kernel@vger.kernel.org Cc: yibin.gong@nxp.com, fugang.duan@nxp.com, l.stach@pengutronix.de, dan.j.williams@intel.com, vkoul@kernel.org, shawnguo@kernel.org, s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, dmaengine@vger.kernel.or, linux-arm-kernel@lists.infradead.org, Philipp Puschmann Subject: [PATCH v4 0/3] Fix UART DMA freezes for i.MX SOCs Date: Thu, 19 Sep 2019 16:29:38 +0200 Message-Id: <20190919142942.12469-1-philipp.puschmann@emlix.com> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For some years and since many kernel versions there are reports that RX UART DMA channel stops working at one point. So far the usual workaround was to disable RX DMA. This patches fix the underlying problem. When a running sdma script does not find any usable destination buffer to put its data into it just leads to stopping the channel being scheduled again. As solution we manually retrigger the sdma script for this channel and by this dissolve the freeze. While this seems to work fine so far, it may come to buffer overruns when the channel - even temporary - is stopped. This case has to be addressed by device drivers by increasing the number of DMA periods. This patch series was tested with the current kernel and backported to kernel 4.15 with a special use case using a WL1837MOD via UART and provoking the hanging of UART RX DMA within seconds after starting a test application. It resulted in well known "Bluetooth: hci0: command 0x0408 tx timeout" errors and complete stop of UART data reception. Our Bluetooth traffic consists of many independent small packets, mostly only a few bytes, causing high usage of periods. Changelog v4: - fixed the fixes tags Changelog v3: - fixes typo in dma_wmb - add fixes tags Changelog v2: - adapt title (this patches are not only for i.MX6) - improve some comments and patch descriptions - add a dma_wb() around BD_DONE flag - add Reviewed-by tags - split off "serial: imx: adapt rx buffer and dma periods" Philipp Puschmann (3): dmaengine: imx-sdma: fix buffer ownership dmaengine: imx-sdma: fix dma freezes dmaengine: imx-sdma: drop redundant variable drivers/dma/imx-sdma.c | 32 ++++++++++++++++++++++---------- 1 file changed, 22 insertions(+), 10 deletions(-) -- 2.23.0