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serial: 8250: Fix lost rx state 

When max_count is reached, the rx loop exits. However, UART_LSR has
already been read so those char flags are lost, and subsequent rx
status will be for the wrong byte until the rx fifo drains.

Reported-by: George Spelvin <linux@horizon.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2016-01-10 14:39:32 -08:00 committed by Greg Kroah-Hartman
parent 3f6b3ce071
commit d22f8f1068
1 changed files with 4 additions and 3 deletions
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7
drivers/tty/serial/8250/8250_port.c
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@ -1478,16 +1478,17 @@ static void serial8250_read_char(struct uart_8250_port *up, unsigned char lsr)
* value, and returns the remaining LSR bits not handled
* by this Rx routine.
*/
unsigned char
serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr)
unsigned char serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr)
{
struct uart_port *port = &up->port;
int max_count = 256;
do {
serial8250_read_char(up, lsr);
if (--max_count == 0)
break;
lsr = serial_in(up, UART_LSR);
} while ((lsr & (UART_LSR_DR | UART_LSR_BI)) && (--max_count > 0));
} while (lsr & (UART_LSR_DR | UART_LSR_BI));
spin_unlock(&port->lock);
tty_flip_buffer_push(&port->state->port);
spin_lock(&port->lock);