serial: xuartps: Fix suspend functionality

The driver's suspend/resume functions were buggy.
If UART node contains any child node in the DT and
the child is established a communication path with
the parent UART. The relevant /dev/ttyPS* node will
be not available for other operations.
If the driver is trying to do any operations like
suspend/resume without checking the tty->dev status
it leads to the kernel crash/hang.

This patch fix this issue by call the device_may_wake()
with the generic parameter of type struct device.
in the uart suspend and resume paths.

It also fixes a race condition in the uart suspend
path(i.e uart_suspend_port() should be called at the
end of cdns_uart_suspend API this path updates the same)

Signed-off-by: Nava kishore Manne <navam@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 0c8baa24ce92e84c7dc1b7cd74ff455f5f5e1e4a..15039d772af0086afc53b7f2ea0cfe20d1f0d2a5 100644 (file)
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1309,24 +1309,11 @@ static struct uart_driver cdns_uart_uart_driver = {
 static int cdns_uart_suspend(struct device *device)
 {
        struct uart_port *port = dev_get_drvdata(device);
-       struct tty_struct *tty;
-       struct device *tty_dev;
-       int may_wake = 0;
-
-       /* Get the tty which could be NULL so don't assume it's valid */
-       tty = tty_port_tty_get(&port->state->port);
-       if (tty) {
-               tty_dev = tty->dev;
-               may_wake = device_may_wakeup(tty_dev);
-               tty_kref_put(tty);
-       }
+       int may_wake;
 
-       /*
-        * Call the API provided in serial_core.c file which handles
-        * the suspend.
-        */
-       uart_suspend_port(&cdns_uart_uart_driver, port);
-       if (!(console_suspend_enabled && !may_wake)) {
+       may_wake = device_may_wakeup(device);
+
+       if (console_suspend_enabled && may_wake) {
                unsigned long flags = 0;
 
                spin_lock_irqsave(&port->lock, flags);
@@ -1341,7 +1328,11 @@ static int cdns_uart_suspend(struct device *device)
                spin_unlock_irqrestore(&port->lock, flags);
        }
 
-       return 0;
+       /*
+        * Call the API provided in serial_core.c file which handles
+        * the suspend.
+        */
+       return uart_suspend_port(&cdns_uart_uart_driver, port);
 }
 
 /**
@@ -1355,17 +1346,9 @@ static int cdns_uart_resume(struct device *device)
        struct uart_port *port = dev_get_drvdata(device);
        unsigned long flags = 0;
        u32 ctrl_reg;
-       struct tty_struct *tty;
-       struct device *tty_dev;
-       int may_wake = 0;
-
-       /* Get the tty which could be NULL so don't assume it's valid */
-       tty = tty_port_tty_get(&port->state->port);
-       if (tty) {
-               tty_dev = tty->dev;
-               may_wake = device_may_wakeup(tty_dev);
-               tty_kref_put(tty);
-       }
+       int may_wake;
+
+       may_wake = device_may_wakeup(device);
 
        if (console_suspend_enabled && !may_wake) {
                struct cdns_uart *cdns_uart = port->private_data;