Patch "serial: imx: Fix DMA handling for IDLE condition aborts" has been added to the 3.14-stable tree

Patch "serial: imx: Fix DMA handling for IDLE condition aborts" has been added to the 3.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    serial: imx: Fix DMA handling for IDLE condition aborts

to the 3.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     serial-imx-fix-dma-handling-for-idle-condition-aborts.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 392bceedb107a3dc1d4287e63d7670d08f702feb Mon Sep 17 00:00:00 2001
From: Philipp Zabel <p.zabel@pengutronix.de>
Date: Tue, 19 May 2015 10:54:09 +0200
Subject: serial: imx: Fix DMA handling for IDLE condition aborts

From: Philipp Zabel <p.zabel@pengutronix.de>

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 <ps.report@gmx.net>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/tty/serial/imx.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -907,6 +907,14 @@ 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) {


Patches currently in stable-queue which might be from p.zabel@pengutronix.de are

queue-3.14/serial-imx-fix-dma-handling-for-idle-condition-aborts.patch
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