aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorJon Medhurst <tixy@linaro.org>2013-12-10 10:18:58 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-25 08:27:12 -0800
commit3bb0df1b71413ae789767d928d9126c5a5cb1e11 (patch)
tree4e74156a819f1ac2df5b519c60ae919c01ed61bd
parent2d36355274980e716b832710e8d18b6396594d4e (diff)
downloadlinaro-lsk-3bb0df1b71413ae789767d928d9126c5a5cb1e11.tar.gz
serial: amba-pl011: use port lock to guard control register access
commit fe43390702a1b5741fdf217063b05c7612b38303 upstream. When the pl011 is being used for a console, pl011_console_write forces the control register (CR) to enable the UART for transmission and then restores this to the original value afterwards. It does this while holding the port lock. Unfortunately, when the uart is started or shutdown - say in response to userland using the serial device for a terminal - then this updates the control register without any locking. This means we can have pl011_console_write Save CR pl011_startup Initialise CR, e.g. enable receive pl011_console_write Restore old CR with receive not enabled this result is a serial port which doesn't respond to any input. A similar race in reverse could happen when the device is shutdown. We can fix these problems by taking the port lock when updating CR. Signed-off-by: Jon Medhurst <tixy@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/tty/serial/amba-pl011.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index e2774f9ecd5..7a55fe70434 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1543,6 +1543,8 @@ static int pl011_startup(struct uart_port *port)
/*
* Provoke TX FIFO interrupt into asserting.
*/
+ spin_lock_irq(&uap->port.lock);
+
cr = UART01x_CR_UARTEN | UART011_CR_TXE | UART011_CR_LBE;
writew(cr, uap->port.membase + UART011_CR);
writew(0, uap->port.membase + UART011_FBRD);
@@ -1567,6 +1569,8 @@ static int pl011_startup(struct uart_port *port)
cr |= UART01x_CR_UARTEN | UART011_CR_RXE | UART011_CR_TXE;
writew(cr, uap->port.membase + UART011_CR);
+ spin_unlock_irq(&uap->port.lock);
+
/*
* initialise the old status of the modem signals
*/
@@ -1636,11 +1640,13 @@ static void pl011_shutdown(struct uart_port *port)
* it during startup().
*/
uap->autorts = false;
+ spin_lock_irq(&uap->port.lock);
cr = readw(uap->port.membase + UART011_CR);
uap->old_cr = cr;
cr &= UART011_CR_RTS | UART011_CR_DTR;
cr |= UART01x_CR_UARTEN | UART011_CR_TXE;
writew(cr, uap->port.membase + UART011_CR);
+ spin_unlock_irq(&uap->port.lock);
/*
* disable break condition and fifos