2022-06-08 03:59:31

by Vijaya Krishna Nivarthi

Subject: [PATCH 1/2] serial: core: Introduce callback for start_rx and do stop_rx in suspend only if this callback implementation is present.

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")
Signed-off-by: Vijaya Krishna Nivarthi <[email protected]>
---
drivers/tty/serial/serial_core.c | 9 ++++++---
include/linux/serial_core.h | 1 +
2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 9a85b41..338ebad 100644
--- 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
--- 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 *);
--
Qualcomm INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by the Linux Foundation.

2022-06-08 16:07:54

by Doug Anderson

Subject: Re: [PATCH 1/2] serial: core: Introduce callback for start_rx and do stop_rx in suspend only if this callback implementation is present.

Hi,

On Tue, Jun 7, 2022 at 11:53 AM Vijaya Krishna Nivarthi
<[email protected]> wrote:
>
> 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")
> Signed-off-by: Vijaya Krishna Nivarthi <[email protected]>
> ---
> drivers/tty/serial/serial_core.c | 9 ++++++---
> include/linux/serial_core.h | 1 +
> 2 files changed, 7 insertions(+), 3 deletions(-)

Reviewed-by: Douglas Anderson <[email protected]>