From 2af7cd68f1ed20e2e72c91988c3d4f457fa29ebc Mon Sep 17 00:00:00 2001
From: Russell King <rmk@dyn-67.arm.linux.org.uk>
Date: Wed, 4 Jan 2006 16:55:09 +0000
Subject: [Serial] Don't miss modem status changes
Reading the MSR register on 8250-compatible UARTs results in any
modem status interrupts being cleared. To avoid missing any
status changes, arrange for get_mctrl() to read the current
status via check_modem_status(), which will process any pending
state changes for us.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
drivers/serial/8250.c | 33 ++++++++++++++++-----------------
1 file changed, 16 insertions(+), 17 deletions(-)
(limited to 'drivers')
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index d2bcd1f87c..076bf848e4 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -1255,25 +1255,24 @@ static _INLINE_ void transmit_chars(struct uart_8250_port *up)
__stop_tx(up);
}
-static _INLINE_ void check_modem_status(struct uart_8250_port *up)
+static unsigned int check_modem_status(struct uart_8250_port *up)
{
- int status;
+ unsigned int status = serial_in(up, UART_MSR);
- status = serial_in(up, UART_MSR);
+ if (status & UART_MSR_ANY_DELTA && up->ier & UART_IER_MSI) {
+ if (status & UART_MSR_TERI)
+ up->port.icount.rng++;
+ if (status & UART_MSR_DDSR)
+ up->port.icount.dsr++;
+ if (status & UART_MSR_DDCD)
+ uart_handle_dcd_change(&up->port, status & UART_MSR_DCD);
+ if (status & UART_MSR_DCTS)
+ uart_handle_cts_change(&up->port, status & UART_MSR_CTS);
- if ((status & UART_MSR_ANY_DELTA) == 0)
- return;
-
- if (status & UART_MSR_TERI)
- up->port.icount.rng++;
- if (status & UART_MSR_DDSR)
- up->port.icount.dsr++;
- if (status & UART_MSR_DDCD)
- uart_handle_dcd_change(&up->port, status & UART_MSR_DCD);
- if (status & UART_MSR_DCTS)
- uart_handle_cts_change(&up->port, status & UART_MSR_CTS);
+ wake_up_interruptible(&up->port.info->delta_msr_wait);
+ }
- wake_up_interruptible(&up->port.info->delta_msr_wait);
+ return status;
}
/*
@@ -1454,10 +1453,10 @@ static unsigned int serial8250_tx_empty(struct uart_port *port)
static unsigned int serial8250_get_mctrl(struct uart_port *port)
{
struct uart_8250_port *up = (struct uart_8250_port *)port;
- unsigned char status;
+ unsigned int status;
unsigned int ret;
- status = serial_in(up, UART_MSR);
+ status = check_modem_status(up);
ret = 0;
if (status & UART_MSR_DCD)
--
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