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 <[email protected]>
---
v1 --> v2:
The ASYNC_CTS_FLOW is set in the `flags` field of the tty_port{},
not in the `flags` field of uart_port{}.
drivers/tty/serial/mxs-auart.c | 14 +++++++++-----
1 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index 2e341b8..3a667ee 100644
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -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);
--
1.7.0.4