serial: core: Introduce callback for start_rx and do stop_rx in suspend only if this...

In suspend sequence there is a need to perform stop_rx during suspend
sequence to prevent any asynchronous data over rx line. However this
can cause problem to drivers which dont do re-start_rx during set_termios.

Add new callback start_rx and perform stop_rx only when implementation of
start_rx is present. Also add call to start_rx in resume sequence so that
drivers who come across this problem can make use of this framework.

Fixes: c9d2325cdb92 ("serial: core: Do stop_rx in suspend path for console if console_suspend is disabled")
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com>
Link: https://lore.kernel.org/r/1654627965-1461-2-git-send-email-quic_vnivarth@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 9a85b41..338ebad 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2214,11 +2214,12 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
        /*
         * Nothing to do if the console is not suspending
         * except stop_rx to prevent any asynchronous data
-        * over RX line. Re-start_rx, when required, is
-        * done by set_termios in resume sequence
+        * over RX line. However ensure that we will be
+        * able to Re-start_rx later.
         */
        if (!console_suspend_enabled && uart_console(uport)) {
-               uport->ops->stop_rx(uport);
+               if (uport->ops->start_rx)
+                       uport->ops->stop_rx(uport);
                goto unlock;
        }
 
@@ -2310,6 +2311,8 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
                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);
        }

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index cbd5070..657a0fc 100644 (file)
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -45,6 +45,7 @@ struct uart_ops {
        void            (*unthrottle)(struct uart_port *);
        void            (*send_xchar)(struct uart_port *, char ch);
        void            (*stop_rx)(struct uart_port *);
+       void            (*start_rx)(struct uart_port *);
        void            (*enable_ms)(struct uart_port *);
        void            (*break_ctl)(struct uart_port *, int ctl);
        int             (*startup)(struct uart_port *);