serial: stm32: add no_console_suspend support

In order to display console messages in low power mode, console pins
must be kept active after suspend call.

Initial patch "serial: stm32: add support for no_console_suspend" was part
of "STM32 usart power improvement" series, but as dependancy to
console_suspend pinctl state has been removed to fit with Rob comment [1],
this patch has no more dependancy with any other patch of this series.

[1] https://lkml.org/lkml/2019/7/9/451

Signed-off-by: Erwan Le Ray <erwan.leray@st.com>
Link: https://lore.kernel.org/r/20200519094104.27082-1-erwan.leray@st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 7d1acb3786b8038ab882edd7bc0a69ce02e615b9..8602ff3573218a4cdf97706602fd150fb73038e2 100644 (file)
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -1424,7 +1424,18 @@ static int __maybe_unused stm32_serial_suspend(struct device *dev)
        else
                stm32_serial_enable_wakeup(port, false);
 
-       pinctrl_pm_select_sleep_state(dev);
+       /*
+        * When "no_console_suspend" is enabled, keep the pinctrl default state
+        * and rely on bootloader stage to restore this state upon resume.
+        * Otherwise, apply the idle or sleep states depending on wakeup
+        * capabilities.
+        */
+       if (console_suspend_enabled || !uart_console(port)) {
+               if (device_may_wakeup(dev))
+                       pinctrl_pm_select_idle_state(dev);
+               else
+                       pinctrl_pm_select_sleep_state(dev);
+       }
 
        return 0;
 }