patch "serial: imx: Fix DMA handling for IDLE condition aborts" added to tty-linus

patch "serial: imx: Fix DMA handling for IDLE condition aborts" added to tty-linus

[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 my tty git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


>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

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>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 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 c8cfa0637128..88250395b0ce 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -911,6 +911,14 @@ 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) {
-- 
2.4.1