The "serial/8250: Use fifo in 8250 console driver" commit
has revealed an issue of not re-enabling FIFO after resume.
The problematic path is inside uart_resume_port() function.
First, when the console device is re-enabled,
a call to uport->ops->set_termios() internally initializes FIFO
(in serial8250_do_set_termios()), although further code
disables it by issuing ops->startup() (pointer to serial8250_do_startup,
internally calling serial8250_clear_fifos()).
There is even a comment saying "Clear the FIFO buffers and disable them.
(they will be reenabled in set_termios())", but in this scenario,
set_termios() has been called already and FIFO remains disabled.
This patch address the issue by reversing the order - first checks
if tty port is suspended and performs actions accordingly
(e.g. call to ops->startup()), then tries to re-enable
the console device after suspend (and call to uport->ops->set_termios()).
Signed-off-by: Lukasz Majczak <lma@xxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 6.1+
---
drivers/tty/serial/serial_core.c | 54 ++++++++++++++++----------------
1 file changed, 27 insertions(+), 27 deletions(-)
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 394a05c09d87..57a153adba3a 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2406,33 +2406,6 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
put_device(tty_dev);
uport->suspended = 0;
- /*
- * Re-enable the console device after suspending.
- */
- if (uart_console(uport)) {
- /*
- * First try to use the console cflag setting.
- */
- memset(&termios, 0, sizeof(struct ktermios));
- termios.c_cflag = uport->cons->cflag;
- termios.c_ispeed = uport->cons->ispeed;
- termios.c_ospeed = uport->cons->ospeed;
-
- /*
- * If that's unset, use the tty termios setting.
- */
- if (port->tty && termios.c_cflag == 0)
- termios = port->tty->termios;
-
- if (console_suspend_enabled)
- uart_change_pm(state, UART_PM_STATE_ON);
- uport->ops->set_termios(uport, &termios, NULL);
- if (!console_suspend_enabled && uport->ops->start_rx)
- uport->ops->start_rx(uport);
- if (console_suspend_enabled)
- console_start(uport->cons);
- }
-
if (tty_port_suspended(port)) {
const struct uart_ops *ops = uport->ops;
int ret;
@@ -2471,6 +2444,33 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
tty_port_set_suspended(port, false);
}
+ /*
+ * Re-enable the console device after suspending.
+ */
+ if (uart_console(uport)) {
+ /*
+ * First try to use the console cflag setting.
+ */
+ memset(&termios, 0, sizeof(struct ktermios));
+ termios.c_cflag = uport->cons->cflag;
+ termios.c_ispeed = uport->cons->ispeed;
+ termios.c_ospeed = uport->cons->ospeed;
+
+ /*
+ * If that's unset, use the tty termios setting.
+ */
+ if (port->tty && termios.c_cflag == 0)
+ termios = port->tty->termios;
+
+ if (console_suspend_enabled)
+ uart_change_pm(state, UART_PM_STATE_ON);
+ uport->ops->set_termios(uport, &termios, NULL);
+ if (!console_suspend_enabled && uport->ops->start_rx)
+ uport->ops->start_rx(uport);
+ if (console_suspend_enabled)
+ console_start(uport->cons);
+ }
+
mutex_unlock(&port->mutex);
return 0;
--
2.40.0.577.gac1e443424-goog
