From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935491AbbGHPvj (ORCPT ); Wed, 8 Jul 2015 11:51:39 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:47917 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933814AbbGHPlH (ORCPT ); Wed, 8 Jul 2015 11:41:07 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Philipp Zabel , Greg Kroah-Hartman , Kamal Mostafa Subject: [PATCH 3.13.y-ckt 26/56] serial: imx: Fix DMA handling for IDLE condition aborts Date: Wed, 8 Jul 2015 08:40:07 -0700 Message-Id: <1436370037-25874-27-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1436370037-25874-1-git-send-email-kamal@canonical.com> References: <1436370037-25874-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13.11-ckt23 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Philipp Zabel commit 392bceedb107a3dc1d4287e63d7670d08f702feb upstream. The driver configures the IDLE condition to interrupt the SDMA engine. Since the SDMA UART ROM script doesn't clear the IDLE bit itself, this caused repeated 1-byte DMA transfers, regardless of available data in the RX FIFO. Also, when returning due to the IDLE condition, the UART ROM script already increased its counter, causing residue to be off by one. This patch clears the IDLE condition to avoid repeated 1-byte DMA transfers and decreases count by when the DMA transfer was aborted due to the IDLE condition, fixing serial transfers using DMA on i.MX6Q. Reported-by: Peter Seiderer Signed-off-by: Philipp Zabel Tested-by: Fabio Estevam Signed-off-by: Greg Kroah-Hartman Signed-off-by: Kamal Mostafa --- drivers/tty/serial/imx.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index b2cfdb6..36e52c2 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -899,6 +899,14 @@ static void dma_rx_callback(void *data) status = dmaengine_tx_status(chan, (dma_cookie_t)0, &state); count = RX_BUF_SIZE - state.residue; + + if (readl(sport->port.membase + USR2) & USR2_IDLE) { + /* In condition [3] the SDMA counted up too early */ + count--; + + writel(USR2_IDLE, sport->port.membase + USR2); + } + dev_dbg(sport->port.dev, "We get %d bytes.\n", count); if (count) { -- 1.9.1