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authorHaavard Skinnemoen <haavard.skinnemoen@atmel.com>2009-06-16 12:02:03 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 15:01:16 -0400
commit0ccad87012c6c2e7446e4dc0f0894cf182a5270a (patch)
treec5fd8d151469b78f5a003a891b75f3446c0f5062 /drivers/serial
parentdc9879291be479e096c5cfac33effc2ade74309b (diff)
atmel_serial: fix hang in set_termios when crtscts is enabled
After enabling hardware flow control, any subsequent termios call may hang waiting for the transmitter to drain. This appears to be caused by a busy-loop in set_termios() waiting for the transmitter to become empty, which may take a very long time (or hang indefinitely) if the device at the other end is blocking us. A quick look through the tty and serial_core code indicates that any necessary flushing (which is optional) has already been done at this point, so there's no need for the driver to flush the transmitter on its own. Fix it by removing the busy-loop altogether. Tested-by: Eirik Aanonsen <eaa@wprmedical.com> Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/serial')
-rw-r--r--drivers/serial/atmel_serial.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index b3497d7e535..338b15c0a54 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -1104,11 +1104,13 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
1104 /* update the per-port timeout */ 1104 /* update the per-port timeout */
1105 uart_update_timeout(port, termios->c_cflag, baud); 1105 uart_update_timeout(port, termios->c_cflag, baud);
1106 1106
1107 /* save/disable interrupts and drain transmitter */ 1107 /*
1108 * save/disable interrupts. The tty layer will ensure that the
1109 * transmitter is empty if requested by the caller, so there's
1110 * no need to wait for it here.
1111 */
1108 imr = UART_GET_IMR(port); 1112 imr = UART_GET_IMR(port);
1109 UART_PUT_IDR(port, -1); 1113 UART_PUT_IDR(port, -1);
1110 while (!(UART_GET_CSR(port) & ATMEL_US_TXEMPTY))
1111 cpu_relax();
1112 1114
1113 /* disable receiver and transmitter */ 1115 /* disable receiver and transmitter */
1114 UART_PUT_CR(port, ATMEL_US_TXDIS | ATMEL_US_RXDIS); 1116 UART_PUT_CR(port, ATMEL_US_TXDIS | ATMEL_US_RXDIS);