linux-kernel - [PATCH 4.1 082/123] Revert "serial: imx: initialized DMA w/o HW flow enabled"

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Date:	Sat,  8 Aug 2015 15:09:20 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, David Jander <david@...tonic.nl>
Subject: [PATCH 4.1 082/123] Revert "serial: imx: initialized DMA w/o HW flow enabled"

4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Jander <david@...tonic.nl>

commit 907eda32a36fcdb979bdb91ea097abb3dd2c23c9 upstream.

This reverts commit 068500e08dc87ea9a453cc4a500cf3ab28d0f936.

According to some tests, SDMA support is broken at least for i.MX6 without
HW flow control. Different forms of data-corruption appear either with
the ROM firmware for the SDMA controller as well as when loading Freescale
provided SDMA firmware versions 1.1 or 3.1.

Signed-off-by: David Jander <david@...tonic.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/tty/serial/imx.c |   15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1132,11 +1132,6 @@ static int imx_startup(struct uart_port
 	while (!(readl(sport->port.membase + UCR2) & UCR2_SRST) && (--i > 0))
 		udelay(1);
 
-	/* Can we enable the DMA support? */
-	if (is_imx6q_uart(sport) && !uart_console(port) &&
-	    !sport->dma_is_inited)
-		imx_uart_dma_init(sport);
-
 	spin_lock_irqsave(&sport->port.lock, flags);
 
 	/*
@@ -1145,9 +1140,6 @@ static int imx_startup(struct uart_port
 	writel(USR1_RTSD, sport->port.membase + USR1);
 	writel(USR2_ORE, sport->port.membase + USR2);
 
-	if (sport->dma_is_inited && !sport->dma_is_enabled)
-		imx_enable_dma(sport);
-
 	temp = readl(sport->port.membase + UCR1);
 	temp |= UCR1_RRDYEN | UCR1_RTSDEN | UCR1_UARTEN;
 
@@ -1318,6 +1310,11 @@ imx_set_termios(struct uart_port *port,
 			} else {
 				ucr2 |= UCR2_CTSC;
 			}
+
+			/* Can we enable the DMA support? */
+			if (is_imx6q_uart(sport) && !uart_console(port)
+				&& !sport->dma_is_inited)
+				imx_uart_dma_init(sport);
 		} else {
 			termios->c_cflag &= ~CRTSCTS;
 		}
@@ -1434,6 +1431,8 @@ imx_set_termios(struct uart_port *port,
 	if (UART_ENABLE_MS(&sport->port, termios->c_cflag))
 		imx_enable_ms(&sport->port);
 
+	if (sport->dma_is_inited && !sport->dma_is_enabled)
+		imx_enable_dma(sport);
 	spin_unlock_irqrestore(&sport->port.lock, flags);
 }
 


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