tty/serial: at91: enable peripheral clock before accessing I/O registers

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@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index ffefec83a02f0e4055fc70662fd5e73dae49574e..fcb08e87873efcfcc96eda6827f552edd7986fd7 100644 (file)
--- 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: