[PATCH 3.16.y-ckt 019/183] tty/serial: at91: enable peripheral clock before accessing I/O registers

From: Luis Henriques
Date: Fri Mar 06 2015 - 06:13:27 EST


3.16.7-ckt8 -stable review patch. If anyone has any objections, please let me know.

------------------

From: Cyrille Pitchen <cyrille.pitchen@xxxxxxxxx>

commit d4f641876a68d1961e30c202709cc2d484f69f6f upstream.

atmel_serial_probe() calls atmel_init_port(). In turn, atmel_init_port() calls
clk_disable_unprepare() to disable the peripheral clock before returning.

Later atmel_serial_probe() accesses some I/O registers such as the Mode and
Control registers for RS485 support then the Name and Version registers, through a call to
atmel_get_ip_name(), but at that moment the peripheral clock was still
disabled.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@xxxxxxxxx>
Acked-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
drivers/tty/serial/atmel_serial.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index ffefec83a02f..fcb08e87873e 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -2605,6 +2605,12 @@ static int atmel_serial_probe(struct platform_device *pdev)
device_init_wakeup(&pdev->dev, 1);
platform_set_drvdata(pdev, port);

+ /*
+ * The peripheral clock has been disabled by atmel_init_port():
+ * enable it before accessing I/O registers
+ */
+ clk_prepare_enable(port->clk);
+
if (port->rs485.flags & SER_RS485_ENABLED) {
UART_PUT_MR(&port->uart, ATMEL_US_USMODE_NORMAL);
UART_PUT_CR(&port->uart, ATMEL_US_RTSEN);
@@ -2615,6 +2621,12 @@ static int atmel_serial_probe(struct platform_device *pdev)
*/
atmel_get_ip_name(&port->uart);

+ /*
+ * The peripheral clock can now safely be disabled till the port
+ * is used
+ */
+ clk_disable_unprepare(port->clk);
+
return 0;

err_add_port:
--
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