Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932360AbbFYKUU (ORCPT ); Thu, 25 Jun 2015 06:20:20 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:39593 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752191AbbFYKDC (ORCPT ); Thu, 25 Jun 2015 06:03:02 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Philipp Zabel , Greg Kroah-Hartman , Luis Henriques Subject: [PATCH 3.16.y-ckt 09/71] serial: imx: Fix DMA handling for IDLE condition aborts Date: Thu, 25 Jun 2015 11:01:48 +0100 Message-Id: <1435226570-3669-10-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1435226570-3669-1-git-send-email-luis.henriques@canonical.com> References: <1435226570-3669-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1969 Lines: 51 3.16.7-ckt14 -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: Luis Henriques --- 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 044e86d528ae..e30e52e378fe 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -913,6 +913,14 @@ 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) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/