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Commit 2af7cd68 authored by Russell King's avatar Russell King Committed by Russell King
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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: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 88026842

drivers/serial/8250.c

+16 −17
Original line number Original line Diff line number Diff line
@@ -1255,15 +1255,11 @@ static _INLINE_ void transmit_chars(struct uart_8250_port *up) 
		__stop_tx(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) == 0)

		return;





	if (status & UART_MSR_ANY_DELTA && up->ier & UART_IER_MSI) {

		if (status & UART_MSR_TERI)

		if (status & UART_MSR_TERI)

			up->port.icount.rng++;

			up->port.icount.rng++;

		if (status & UART_MSR_DDSR)

		if (status & UART_MSR_DDSR)
@@ -1276,6 +1272,9 @@ static _INLINE_ void check_modem_status(struct uart_8250_port *up) 
		wake_up_interruptible(&up->port.info->delta_msr_wait);

		wake_up_interruptible(&up->port.info->delta_msr_wait);

	}

	}





	return status;

}



/*

/*

 * This handles the interrupt from one port.

 * This handles the interrupt from one port.

 */

 */
@@ -1454,10 +1453,10 @@ static unsigned int serial8250_tx_empty(struct uart_port *port) 
static unsigned int serial8250_get_mctrl(struct uart_port *port)

static unsigned int serial8250_get_mctrl(struct uart_port *port)

{

{

	struct uart_8250_port *up = (struct uart_8250_port *)port;

	struct uart_8250_port *up = (struct uart_8250_port *)port;

	unsigned char status;

	unsigned int status;

	unsigned int ret;

	unsigned int ret;





	status = serial_in(up, UART_MSR);

	status = check_modem_status(up);





	ret = 0;

	ret = 0;

	if (status & UART_MSR_DCD)

	if (status & UART_MSR_DCD)