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authorJon Medhurst <tixy@linaro.org>2013-12-10 10:18:58 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-25 08:49:29 -0800
commit81fd649b0a6340d0e311deedc5dd156c36873450 (patch)
tree8285366b4075888329d80eb5c3c091cd335f144c
parent1a912f30eff840b2509762f91f2eaf5769211920 (diff)
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 aaa22867e656..1440d0b4a7bc 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1537,6 +1537,8 @@ 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);
@@ -1561,6 +1563,8 @@ 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
*/
@@ -1629,11 +1633,13 @@ 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