[PATCH AUTOSEL 4.19 010/191] serial: uartps: Fix suspend functionality

Sasha Levin
2019-11-10T02:40:35Z

From: Nava kishore Manne <nava.manne@xilinx.com>

[ Upstream commit 4b9d33c6a30688344a3e95179654ea31b07f59b7 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tty/serial/xilinx_uartps.c | 41 +++++++++---------------------
1 file changed, 12 insertions(+), 29 deletions(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 77efa0a43fe76..66d49d5118853 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1279,24 +1279,11 @@ 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);
@@ -1311,7 +1298,11 @@ 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);
}

/**
@@ -1325,17 +1316,9 @@ 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;
--
2.20.1