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serial: mxs-auart: fix the wrong RTS hardware flow control 

Without checking if the auart supports the hardware flow control or not,
the old mxs_auart_set_mctrl() asserted the RTS pin blindly.

This will causes the auart receives wrong data in the following case:
   The far-end has already started the write operation, and wait for
the auart asserts the RTS pin. Then the auart starts the read operation,
but mxs_auart_set_mctrl() may be called before we set the RTSCTS in the
mxs_auart_settermios(). So the RTS pin is asserted in a wrong situation,
and we get the wrong data in the end.

This bug has been catched when I connect the mx23(DTE) to the mx53(DCE).

This patch also replaces the AUART_CTRL2_RTS with AUART_CTRL2_RTSEN.
We should use the real the hardware flow control, not the software-controled
hardware flow control.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Huang Shijie 2012-08-08 10:37:59 +08:00 committed by Greg Kroah-Hartman
parent 7d9739cd6b
commit 0059202101
1 changed files with 9 additions and 5 deletions
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14
drivers/tty/serial/mxs-auart.c
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@ -73,6 +73,7 @@
#define AUART_CTRL0_CLKGATE (1 << 30)
#define AUART_CTRL2_CTSEN (1 << 15)
#define AUART_CTRL2_RTSEN (1 << 14)
#define AUART_CTRL2_RTS (1 << 11)
#define AUART_CTRL2_RXE (1 << 9)
#define AUART_CTRL2_TXE (1 << 8)
@ -259,9 +260,12 @@ static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl)
u32 ctrl = readl(u->membase + AUART_CTRL2);
ctrl &= ~AUART_CTRL2_RTS;
if (mctrl & TIOCM_RTS)
ctrl |= AUART_CTRL2_RTS;
ctrl &= ~AUART_CTRL2_RTSEN;
if (mctrl & TIOCM_RTS) {
if (u->state->port.flags & ASYNC_CTS_FLOW)
ctrl |= AUART_CTRL2_RTSEN;
}
s->ctrl = mctrl;
writel(ctrl, u->membase + AUART_CTRL2);
}
@ -359,9 +363,9 @@ static void mxs_auart_settermios(struct uart_port *u,
/* figure out the hardware flow control settings */
if (cflag & CRTSCTS)
ctrl2 |= AUART_CTRL2_CTSEN;
ctrl2 |= AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN;
else
ctrl2 &= ~AUART_CTRL2_CTSEN;
ctrl2 &= ~(AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN);
/* set baud rate */
baud = uart_get_baud_rate(u, termios, old, 0, u->uartclk);