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serial: imx: re-enable DMA support without hardware flow control

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The commit enabling DMA support even if no flow control is present
was reverted on the grounds that it uncovered a number of bugs in
the code that lead to hanging tty devices and/or missing characters.

After tracking down the issues it is clear that those were generic
bugs and had nothing to do with flow control being present or not,
only that allowing DMA without hardware flow control increased
the exposure of that code a lot.

Now that those bugs are fixed, it should be safe to re-enable DMA
support.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Lucas Stach 2015-09-04 17:52:42 +02:00 committed by Greg Kroah-Hartman
parent 905c0decad
commit 7e11577ef6
1 changed files with 8 additions and 7 deletions
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15
drivers/tty/serial/imx.c
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@ -1125,6 +1125,11 @@ static int imx_startup(struct uart_port *port)
writel(temp & ~UCR4_DREN, sport->port.membase + UCR4);
/* 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);
/* Reset fifo's and state machines */
i = 100;
@ -1142,6 +1147,9 @@ static int imx_startup(struct uart_port *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;
@ -1312,11 +1320,6 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
} 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;
}
@ -1433,8 +1436,6 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
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);
}