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[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>
This commit is contained in:
Russell King 2006-01-04 16:55:09 +00:00 committed by Russell King
parent 88026842b0
commit 2af7cd68f1
1 changed files with 16 additions and 17 deletions
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33
drivers/serial/8250.c
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@ -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;
wake_up_interruptible(&up->port.info->delta_msr_wait);
}
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);
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)